SC running "too damn hot": Mechanics stumped, So am I !
 

For years, my 83SC has been running too hot in my opinion. I'm seeking off the wall ideas here...

Everytime it's running 80 mph+ sustained on the highway, in the summertime, it's reaching 230 or so. Gentle use is not an issue, winter/lower outside temps make it fine too...

The car lived in california for 7 years (up to 110F outside) and now in Florida (80+ even in winter!! often 90F) so it's always dealing with hot air. It's reached 170000 miles without ever breaking down so it's not like those occasional temps are killing it - but it annoys me and it makes the car useless at the race track...

The car came with an upgrade to the trombone, a genuine Carrera fender cooler and I had a bosch Fan rigged on it with an adjusteable temps switch, and barricaded all around with plastic sheeting to ensure the air would flow through and not around the cooler.

The oil lines are not crushed and in fact fairly new. There is flow to the front cooler, and both engine cooler and fender cooler thermostats are new as of last week. The cooler does help stabilize things and like I said, daily driving is not a problem, but high speed crusing and hard driving will cause 230+ and track days 250F easy after 20 minutes or so...

Given all the above, what else could it be? Where should I point my IR gun to match the gauge? I can get 5 different readings depending on where I point it - the housing of the oil temps switch is not quite as hot as the gauge but close (-20F)... yesterday I put the numbered gauge of a 77 911 (from a friend's) on my car and it read 20F lower than mine. But I know some gauges must be calibrated to their senders so I am not sure that was a valid test.

Assuming the gauge does not lie (most IR gun measurements confirm the temps, there or thereabouts), what else could it be ??? And where should I shoot to match a normally functioning gauge ?

PS: My mechanic installed a front cooler (race style) in series with the fender cooler, and put a huge fan on it... it made ZERO difference ! Yet I got plenty of oil frow to the front !

PPS: Is it OK to put the oil pressure sender of a 84-89 on an 83 ? (that is all I had with me) The only difference as far as I can tell is the connector, seems to work great ! Thanks !

Check the internal thermostat on the engine. I had a similar situation, and mine didn't open.

is it running lean? could a lean A/F mixture drive up temps? Or a blocked exhaust system?

Do a search on the subject, but I was under the impression that the temp gauge on the dash ran cooler than the temp readings taken on the engine with an IR gun. If this is the case, then the likely culprit is the sender and/or gauge, which can be replaced fairly inexpensively. The other thing to check is the condition of the cooling fins on the top of the motor. Many have discovered rats nests on top of their engines.

You certainly have plenty of oil cooling.
some things that come to mind
*early SC's had a high speed overheating problem that arose form issues w/ the pressure relief valves and the venturi at the sump pickup. Yours should be ok but it's something to check.

*is the oil pump up to spec?

*air/fuel and timing in spec?

* any mice subleting on top of the cylinders?

Bill is right. If the oil thermostat is opening (easy to tell...are your front cooler lines hot?) then my money is on the upgraded sump plate required on early SC's for exactly this symptom. Do a search.

Make sure you have flow not only _to_ but _through_ the cooler. If the cooler itself is cool thought the lines are hot, it means that you have enough of an obstruction--a moderate dent, say--somewhere in the hard lines to persuade the oil to bypass back through the thermostat rather than pushing its way through the cooler. You'll think it's "just a dent, not crushed," but the oil thinks, "That's too much work to get past with adequate pressure to continue through the little tubes in the cooler."

I say that because it's a problem I currently have and am about to cure--a moderate, hey-no-problem oil-line crimp that allows enough oil through to heat the hard lines but won't push through my 18"-wide B&B front-mounted cooler.

Re: SC running "too damn hot": Mechanics stumped, So am I !
 

Up until I read this part I thought "yeah, sounds just like my SC, put in a front oil cooler":

That's just not right.

How did you check oil flow to the coolers?

Time to get a temp measurement setup that will allow you to take measurements both while the car is sitting still and while it is moving.

I used a Fluke 2-channel digital multimeter and two thermocouples like this one:

http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=23290%28FlukeProducts%29 &catalog_name=FlukeUnitedStates&Category=PRTP(FlukeProducts)

If you don't have a 2-channel fluke multimeter, you will need two one-channel multimeters. They don't have to be Fluke, you can buy an adapter kit to use thermocouples with non-Fluke multimeters:

http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=9187%28FlukeProducts%29& catalog_name=FlukeUnitedStates&Category=PRTP(FlukeProducts)

You can drop one of the thermocouples down into the oil filler tube to check oil temp while idling. This will tell you exactly what your temps are, so you can calibrate your dash gauge.

You need to check your oil line temps, but you need to check them while moving. Neither of those coolers will do much if you are sitting still. Use foil HVAC tape (the metal stuff) to tape one thermocouple to the supply tube and one thermocouple to the return tube, in the passenger front fender. Run the thermocouple wires to your digital multimeter placed on the passenger seat. Now drive and get it up to highway speeds. What sort of temp differences are you seeing between supply and return? If you aren't seeing at least 20 degrees then you either have ineffective coolers for one reason or another or you aren't getting enough oil flowing through the lines.

For reference, I have just a front-mounted B&B cooler (the big one) and the hottest that my car has been since installing it is 235 on the track, and that was on a 105 degree day at 4500 ft with 10% humidity. Most days it is around 200. Before installing that front mounted cooler I had a Carrera cooler and the car regularly would hit 250 after 15 minutes on the track, at which point I would bring it in.

Hope this helps,

Jeff

My buddy had a similar issue and discovered that his fan belt was slipping (But remained quiet), as it was old and hard and not getting the cool air to the cylinders and on-engine oil cooler. He replaced the fan belt and properly tightened it and the issue went away.

I know it is something simple, but its worth trying.

Good luck.

you have a cooler and fan, but you probably still don't have much airflow through the cooler. cut the back of the headlight bucket out and make yourself a headlight ring with a screen in it for racing. cut a section out of the front valance above the fog light too. at speed, the fan doesn't help, you need more airflow.

Wow, lots of brains at work there, thanks guys... I appreciate the help !

Bulk reply:
>Check the internal thermostat on the engine

Like I said, that was replaced with a new one, both were, they both flow..

> is it running lean? could a lean A/F mixture drive up temps? Or a blocked exhaust system?

Not as far as I know, it's been like that since 1996, it would have blown by now if running lean permanently. The analyzer says it's fine as of last tuneup, 2 months ago.

>Many have discovered rats nests on top of their engines.

I'm one of them, my ex 73.5 T had a putrefied rat over the fins, it came from a barn though. This car does not... I did not think history would repeat itself, but..... how hard is it to check for rat remains without dropping the motor ? Last time I found a rat it was during a complete engine out overhaul. Ideas ?

>is the oil pump up to spec?

I cannot answer that. I can tell you I've got plenty of oil pressure, so I assume so, would that be a good indication ?
For a car with 170K miles, I still get 1 bar over each 1000 rpm... Not bad ! (i.e. 4 at 3000rp, 5 at 4000 rpm etc, when hot. when very hot, I'm still reading more than one bar per 1000 rpm)

>If the oil thermostat is opening (easy to tell...are your front cooler lines hot?) then my money is on the upgraded sump plate required on early SC's for exactly this symptom

Yes, I mentioned the lines are way hot, 220 in, 180/190 out..
The upgraded sump plate I thought was for early SCs, my car and engine are 83, last ones made. That needs upgrading too ? If so, please confirm ! I'll do it gladly!

>Make sure you have flow not only _to_ but _through_ the cooler

Hmm, good one Steve... I need to recheck that, but I am pretty sure I shot the cooler itself and got solid 180/220 readings. Lots of variation there shooting thru the fins ! Of course I cannot trace the entire cooler route with my IR gun, the damn fins are in the way! Could be a partial cooler blockage and then the oil would flow thru the T'stat..possibly... But I do see a variation in/out, 20 to 40 degrees or so between the in and out lines... So I think it does work. Is that enough of a differential to prove it flows through? I'll remeasure !

>Up until I read this part I thought "yeah, sounds just like my SC, put in a front oil cooler"

Jaydubya, yes, he tested that, said the cooler looked like a brick on the nose of my SC and made no difference anyway. Mind you, that was before he replaced the engine cooler thermostat (the one behind the motor, not the one controlling flow to the front). There was flow to the new "test" cooler, but apparently, too little too late. Either way, I still think a normal SC cooling system should run more efficiently even without a front cooler. Dont you ?

>discovered that his fan belt was slipping (But remained quiet),

Not a bad thought ! It does not seem to slip when I turn it by hand - like to adjust valves - but I will replace it anyway, I've got spares galore, thanks for the tip !

> John walker (just above):
Thanks. The bucket holes idea will probably help at the track, I thought about it and generaly also removed the front reflector on track. It is true that the fan works best in traffic conditions or slower speeds. I still need a solution for non-track high speed driving though - by high speed I mean freeway - the cops require 2 headlights there ;-)

I am starting to believe that maybe it's "normal" after all, it's always been in hot climates and my 912 is not any cooler these days. But you've given me lots of thing to try, and I appreciate your help... I'm going to order a new sender anyway, and try to get precise measurements !

By the way, nobody mentioned where I should shoot the IR gun to match the gauge the most accurately. Anyone ?

The mouse-nest test: pull the alternator, which is an easy job.

You can also, if you have a small and bright flashlight and a good gooseneck mirror, do a reasonably good job of peering in through the fan blades.

One more, check your temp sensor. I had a running hot problem and found the temp sensor was off by 30 degrees. I tested it by boiling a pot of water and dropping the sensor in it while still hooked up to the gauge 242 degrees to my astonishment.
Good luck!

On the external thermostat housing the is a spring loaded thermostat on the side and then a spring loaded pressure piston on the bottom. I'm not sure how the piston works, but I wonder if it didn't open all the way if you would have a restricted flow returning to the oil tank? I also notice the piston is no longer available but the spring is.

Isn't there a chance there is some sludge and grime - from both the breather or return tubes that has distributed over the cyl cooling fins ? Older motors - with various small leaks contribute to grime and prevent the fan from doing it's job effectively. On my SC - I never succeeded more than 60 % in keeping a clean engine - and it bugged me.

Curious also if a 964 curved blade fan would do you some good in sunny Florida...more CFM thru the fins would likely have an effect at the temp gauge.. I'm not sure if it's easy swap.

___________

'82 Targa - sold
'80 928

I chased down this same exact problem on my SC, turned out the gauge was wrong!! Since you checked it with an IR gun, and the temps were 190/220, I would look at the sender/gauge. Does your have the arch needle, or the numbers on the gauge? You can upgrade both for a small fee..

Hmm, another good idea on the boiling water ! I will wait until I receive the new sender (from pelican, it'll take a week at least ;-), there must be a crush washer there and if I pull it to test and put it back on, it might leak afterwards ? But good one, I will do that !! As well as peering through the blades and replacing the fan belt ! All the easy stuff ;-) the rest is beyond my skill level !

Everyone raves about the Carrera cooler upgrade for the SC - I found it to be mediocre at best. Sure it's an upgrade over the trombone, but it does not by any means eliminate hot running under all conditions. My street temps and freeway temps went down, but it was not much help at all on the track. Even on the street I would routinely hit 235-240 up a hill etc.

Make sure your gage is reading properly, then check the temp drop across the Carrera cooler at speed. If you are getting 20-30 degrees drop across the cooler, that's all you can expect.

Agree that the Carrera cooler, which I used to have in my modified '83 SC, is not much of an improvement over the near-usesless 'bone.

Greg,

Let’s not rush out and buy much stuff. You have the tool to do some serious diagnosis first.

Your first order of business will be to calibrate your temperature gauge. I would do that off the car for best accuracy. All it takes is the sending unit, the temperature combination instrument, a 12 V battery (a dry cell will work), some little electrical jumper wires (Radio Shack), some cooking oil, a small pan and a thermometer. Tie the temperature sender to the thermometer and use them to stir the cooking oil.

Your instrument has some small calibration marks visible when viewed at an angle. Reference to them. Find some non-permanent clear tape and make a tape cover for the temperature gauge. You can now take a marker and make calibration marks on the tape. Use your IR instrument to check the cooking oil temperature also

Reinstall everything and you now have a calibrated gauge and confirm your IR agrees with a real thermometer. (You can calibrate the thermometer with boiling water (+212F) and an ice-water mix (+32F).


With your IR gauge, measure the temperature of the oil pipes to and from the cooler. Keep the revs high with the hand throttle. You may have to mask one with a piece of paper to read the other accurately and vice versa. What is the difference when the engine is hot and the fan on?

Compare these temperatures to the temperature of the bottom chamber of the cooler. Is the bottom of the cooler lower temperature than either of the two pipe readings or in between?

With the engine still hot and revved up, what is the temperature of the oil tank compared to your calibrated instrument?

Best,
Grady

Guys,

For track use, try the

“Rubbermaid Solution”


http://forums.pelicanparts.com/uploa...1153751331.jpg


For less than $100 you can solve the problem at the track.

Best,
Grady

Am I the only one who thinks 230 is not too hot driving fast?

Not getting full advance will make an engine run hot at sustained highway speeds (i.e. high RPM's). I've seen this on high mileage cars with mechanical advance.

I've seen advance mechanisms that were so rusty, their movement was restricted.

Also, I've found the springs that hold the mechanical advance weights inboard at idle are worn or stretched. This allows the weights to swing out a bit at idle. In this condition; when the timing is set at idle all looks good. But when you rev the engine, the weights hit the outboard stops before full advance can be achieved. My fix was to replace the springs, or just bend the spring ends in a little.

Good Luck!:)

Sorry, I missed the part about the new engine thermostat. Did you have to drop the engine to change it?

Ok, thanks guys! Grady, I will try all that this week end, I appreciate the breakdown of to-do stuff! Pat, partial drop only. Stealth, it is too hot if you believe the crazy low numbers I've read on this board ! The alternate theory is that 95% of the SC owning board members have a faulty temps gauge and I am fine ;-)

Goth, the distributor is a good theory. I had advance problems with it in the past (high idle) and it was cleaned up at the time - 10 y ago ! I will test advance with my light gun as well, I'll have to look up the specs (don't remember offhand, the 356/912 numbers keep popping up).

I got to drive it to work today, and the new temps controlled fan switch on the cooler does help a lot in town and at lower speeds, say <50 mph. The temps are rock solid then, 90C, 210F , first white bar. Once at 80 mph, it makes no difference anymore, I guess the airflow at speed distubs the little fan blades enough to cancel their effect, I was running 220/225 on this foggy and relatively cold morning (70s) and I am pretty sure it'll be 230 or more tonight when it gets hotter out there. I need more airflow ! The little scoop thing looks awful though. I might punch holes in the valence and route some air or something ! But first things first, I will check the gauge and sender !

Here is an off the wall thing to check, I had a 2.7L that ran hot when I purchased it. t turned out that someone had installed the air flow deflectors that go between the cyliders backwards! Instead of installing them from the bottom up they put them in top down wich basically stopped the air from the engine fan from being directed through the cooling fins of the cylinders. This is easy to spot, just look up from the bottom at the barrels of the cyliders to see that these air deflectors are inserted from the bottom. To really see how they are installed also look at the top of the cylinders (#1, 2 and 3) by removing the air diverter cover that sends air to your heater blower on the left side of your engine, if you take this cover off (it's right behind and just up from your distributor) you will be able to see inside the air housing behind the engine fan. Once this cover is removed you have easy line of sight to the top of the barrels for cyl 1,2,3 - it's good idea to look in here anyway (as already mentioned) to be sure you have NO obstructions to the top of your cooling fins. Mice nest, dirt, rags, ...

Good luck.

If I read correctly there are 3 oil coolers on the car, 1 engine, 1 fender and 1 front. W/ that much cooling you should be running near 190&deg F most of the time.

That is way more than enough cooling for a stock car on the hottst day if everything is functioning properly.

Yes, check the oil feed and returns for temp first, but if you have good flow then there is a problem inside the engine.

It could be
fuel/air ratio
ignition timing
internal oil blockage/malfuction
piston/cylinder/ring issues

or it could be a bad gauge /sensor

>If I read correctly there are 3 oil coolers on the car, 1 engine, 1 fender and 1 front. W/ that much cooling you should be running near 190° F most of the time.

That was temporary. As of now the car has only the stock engine cooler + the carrera fender cooler with an automatic fan on it.

The distributor post really got me wondering. I'll me timing it at 6000 rpm this w/e ! It will make my neighbors happy ! ;-)

Still thinking that if it's any of the above scarier issues, it's lived that way till 170K miles without missing a beat! Not bad ;-)

And let me say "thanks" as well since I'm chasing down my hot-running 3.0 problems, too. Lots of good advise guys!

Greg,

Knowing that you are reading the temperature correctly is always the best place to start. As you said it has run 170K this way with no problems.

Good to see 912 caretakers.

What I am angling for with my proposed measurements is there are some defective Carrera oil coolers where the oil can bypass from the inlet chamber on top of the cooler to the outlet chamber on top. The two chambers are only separated by a partition that apparently weren’t all properly sealed (brazed). This allows the hot oil to come in the inlet and go out the outlet while the fins (and bottom chamber) stay relatively cool with only some oil passing through the cooler.

I would have thought that your temporary additional cooler would have shown a dramatic change in temperature if this were the case.


The temperature sender measures the oil at its coolest. This is after the front cooler and the engine cooler. If the engine cooler is not functioning, the oil temperature measured by the gauge should be about the same or slightly higher than the oil in the tank. The reasons for the engine cooler to not function can be the thermostat, debris on top of the cooler or just oil & dirt.

When you did your partial drop for the thermostat, did you remove the little plastic cover for the cooler and look?

I also agree that timing and mixture are also possibilities but first things first.

A good improvement for you is to find a used crank pulley (134 mm dia.) with A/C shiv from a ’78-’79 911SC. This will replace your pulley (127 mm) and turn your engine cooling fan 1.82:1 ratio (you have 1.68:1). Not only will this cool the hottest parts of the engine (heads and cylinders) but it will reduce the thermal load on the oil coolers. It has the added advantage of improving you’re A/C. (You want the same diameter A/C pulley.)

Porsche was changing the fan size, number of blades and ratio to try and comply with German sound regulations. This was at the expense of the needed cooling here in the US.

You should also try the Rubbermaid solution. It is remarkably effective and cheep. Go get the parts and set the water bag behind the seats and try it on the highway on a hot day. You will be amazed. It isn’t practical for normal highway use but is a savior at DEs.

Best,
Grady

Greg, I just lived through the same situation with my 73T and it was the distibutor advance mechanism as stated in another post. When the car heats up have a timing light with you and check the idle timing. My problem only showed up when the car was hot. If its off your advance weights are mucked up or have a problem with the springs.

Good luck, Joe

Thanks again to all of you ! I would dearly like to "fix" something that 3 mechanics have not been able to! I will do the timing first thing tonight when I get home and the car is fully warmed up (more like 230), and I will probably make my neighbors happy with a 6000 RPM burst! That SC motor is loud ;-)

Of all I heard - all valid ideas - the distributor strikes me as the first one to try because I know it was gunked up in the past and it's been a looong time since it was serviced.

My plan is as follows, please correct if I am wrong: (83 Sc w/ dual vacuum ports)
- unplug both vacuum lines from the distr, plug the lines (?)
- set idle at 900 rpm if it's not there when unplugged
- set timing light and check for 5 BTDC at idle
- Check advance at 6000 rpm and hope for 35-36

I saw much lower #s on the manuals, 20 something - I guess that is with the lines connected? Why the huge difference ?

Then I will move on to the gauge, sender, inspection of the tin and cylinders, temps reading on the cooler, not necessarily in that order ! Once more, I am very grateful for your collective help! Results soon !

Alternate Cooling
 

I added "heet sheets" and the "cooler collar" to my 2.4L and I get a needles worth or two of cooling from these easy add-ons.

I did see in a competitors catalog a very nifty black plastic air scoop that replaces the bumper bellows on the passenger side that directs air flow over the front inner fender cooler.

I would agree with most here on checking the thermostat though.

Good luck

Bob
73.5T

I'm at work and have to type fast, but don't do the 6,000 RPM thing, :eek: It should reach full advance way before 4,000 RPM. You can just increase RPM slowly until the timing light shows no more advance.

Another option and this is what I usually do:

1. Engine off.
2. Suck on the vacuum line going to the can on the distributor, then put tongue on tip of hose, should hold vacuum (laugh if you must, but it works when you don't have a vacuum gage). :p If it does not hold vacuum then replace vacuum canister.
3. Pop the distributor cap.
4. Manually turn the rotor until the weights are at the outer stops, then slowly release. The weights & rotor should have returned to the inner most stop with no notable friction. If not, then lube and/or bend spring ends in or replace springs as needed.
5. Reset base timing.

Hope this helps :)

There seems to be a concensus about the retarded timing creating a HOT engine. I am not seeing the fact in this point. For example, adding more advance means you capture more mixture to burn - which gives you the added acceleration that we all enjoy. More acceleration almost always means more heat.

But guys indicate that they've seen drops on their temp gauges -

after factoring in more advance
http://www.pelicanparts.com/support/...amingdevil.gif.

_________________

'82 Targa - sold
'80 928

Late ignition is less efficient use of the same given energy. Late ignition does not help the piston change direction at TDC, and at BDC piston is coming up while hot exhaust is still trying to get out.

Update:

Got home, pulled th vac lines, plugged them, and reduced idle to 900 rpm.

The car idles at 3 degrees BTDC... ??? (edit) make that 5 even with the new belt and less shaking...

At 3000 RPM = 18 BTDC
At 5000 rpm = 20-22 BTDC, harder to tell

Pretty much spot on with the specs book but I cannot reconcile those numbers with the 35 numbers I've seen here, maybe that was not for a 2 vacuum line distributor ?

OTOH, i may have found the problem ! The belt - at 5000 rpm - while my wife was on the throttle blowing my eardrums away - looked like uncooked spaghetti doing figure eights !!!

it looked almost fine at 3000, but at 5000 all bets are off. Maybe the belt is worn and slips (it slipped a fair bit when I turned the motor by hand to find TDC), even though tension is perfect !

So, off with the belt.. Let me know about the #s in the meantime if you could !! Thanks guys !

Sounds like the belt is too loose or has generally gone tits-up. There could be maybe a bit of whip--variation from an absolutely straight path--at high rpms, but only what you'd call "a little bit of flutter." Definitely not what it sounds like yours is doing.

As for the timing numbers, idle should be a solid five degrees, as I remember. It's a bit hard to pin down the numbers at high rpms, but at 750/900 rpm, either it's five degrees solid or it's mis-timed.

You will have responses, I'm sure, from far more knowledgeable penguins, or pelicans, or whatever they are.

Previous post just reminded me of something...Thanks!

A common symptom of the mechanical advance springs being too loose is the base timing at idle is unstable. Once you fix the springs, it stops jumping around.

Ok, I cheked the distributor and no sticking... decent vacuum too (line stuck to my tongue - if the wife saw me do that she'd know I've gone over the edge).. The base timing seems rock solid now, I guess the slipping/jumping belt did throw me off initially... 5 degrees, rock solid at idle - did not have the heart to retry 5000 at 10 PM, I will tomorrow. I put in a new belt, the old one looks great still, but with the new one at the same tension and deflection, I can turn the motor easily while before it took some serious pinching... And it's not too tight either, so I guess fresher rubber grips better... That's #1 done, that's it for the night, new belt and correct timing, going for a run tomorrow and will remeasure all temps...