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

[Grady Clay]

Guys,

For track use, try the

“Rubbermaid Solution”





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

Best,
Grady

[stealthn]

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

[Goth]

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...

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!

[patkeefe]

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

[Deschodt]

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 !

[scarceller]

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.

[Bill Verburg]

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

[Deschodt]

>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 ;-)

[s2per]

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

[Grady Clay]

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

[TargaT]

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

[Deschodt]

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 !

[Sunroof]

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

[Goth]

I'm at work and have to type fast, but don't do the 6,000 RPM thing, 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). 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

[Duckworth]

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
.

_________________

'82 Targa - sold
'80 928

[Goth]

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.

[Deschodt]

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 !

[Formerly Steve Wilkinson]

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.

[Goth]

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.

[Deschodt]

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...