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

[Deschodt]

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 !

[patkeefe]

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

[s5uewf]

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

[JP911]

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.

[Bill Verburg]

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?

[Howard M]

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.

[Formerly Steve Wilkinson]

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.

[jaydubya]

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

Originally posted by Deschodt
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 !

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

[Noel]

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.

[john walker's workshop]

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.

[Deschodt]

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 ?

[Formerly Steve Wilkinson]

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.

[Jon Merck]

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!

[Mysterytrain]

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.

[Duckworth]

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

[rattlsnak]

Originally posted by FSTNBLK
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!

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..

[Deschodt]

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 !

[jaydubya]

Originally posted by Deschodt
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 ?

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.

[Formerly Steve Wilkinson]

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.

[Grady Clay]

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