Running Hot at DE

DSPTurtle · 06-01-2008, 10:24 AM

Ran my first DE yesterday at Sebring. What a blast!!! One little problem with the car... the temp gauge ran in the middle of the yellow block the entire time we were out there. First time we pulled into the pit to let it cool for about three minutes and it came out of the yellow zone onto the third hash mark so we went back out. It immediately went back into the middle of the yellow zone. Really made it tough to concentrate and run full out.
During our first break I bled the cooling system and popped off the reservoir cap. The fans were working fine even after I shut the car off they kept running. Don't think the fans are the issue. Plenty of coolant in the system. I have the lower temp fan switch and on the road it typically never gets farther than just over the first hash mark. Oil pressure stayed perfect the entire day. But the temp gauge just stayed in the middle of the yellow field for the rest of all the runs. I kept going but really don't want to do that again.
Anyone have any ideas on how to get the cooling system to be more efficient for DE days? The rest of the 944's there said they were never getting past the third mark so it has to be something with the car. I have owned the car since 1985 and have had the radiator replaced over the years with OEM parts.
It has the turbo water pump, lower fan switch and relatively new hoses. I bled the air out of the system (not much in there and did not make a difference) and running good coolant.
Any ideas will be greatly appreciated as I had way too much fun to not go back out there!!! Anyone that has been to Sebring knows that you are flat out in fourth gear about three different times through the course so it is not like it was a lowspeed/low airflow through the radiator.
1983 (Gen 1) 944. No mods other then a lightweight flywheel and sport clutch with no catalytic converter.
Thanks in advance.

924Sman · 06-01-2008, 10:47 AM

A couple of things you can do.....make sure the radiator is good and clean, no "love bugs" stuck in the fins. Adding Water Wetter to the coolant will also help. The oil viscocity can cause a rise in temp. If by chance you have winter oil in try 50w if not already in there.

Could be the flywheel, it is now running higher RPM's which creates more heat. And finally.....DRIVE FASTER!!.....j/k

Dal

HondaDustR · 12:49 PM

Maybe a bad temp guage sender or a bad ground that's causing the guage to give a false reading, which the higher temps make worse.

DSPTurtle · 06-01-2008, 01:09 PM

Running Mobil 1 15W50. I am thinking about changing the theromostat. Do we have one or two when running the turbo water pump? The PP parts catalog seems to list two???
Also, where is the temp sender? I think cleaning the ground is a great idea but don't know where it is???

HondaDustR · 06-01-2008, 05:58 PM

It is a seperate 1 terminal sensor that screws into the engine block just behind the DME temp sensor thats under the cyl #1 part of the intake manifold.

I have no idea where the ground for the instruments is.

924Sman · 06-02-2008, 02:41 AM

To find thw grounds, look at the light brown wires and follow them to a chassis/structural member.

Here is a diagram but think it is for an s model but most are the same.

Dal

DSPTurtle · 06-25-2008, 08:53 AM

This weekend will be the test for all the stuff you guys recommended. I had to buy two different t-stats... even though both were marked 71C/160F one opened at 165 and the other at 175. I also checked the old one... it seemed to be a little cocked, but who knows if it was enough to cause the problem???
I have installed the new t-stat after using a cooling system cleaner/conditioner (Zertex) and then rinsing everything out really well. I used 2/3 of a gallon of anti-freeze (about a 40% mix), distilled water and a bottle of water wetter.
Everything seems about the same after driving it some more but never really laid into like on the track so I won't know if this all helps until Saturday.
Thanks for all the advice and helpful tips... hopefully this will be a Pelican story with a happy ending!!! Or it will all blow up and then I will have a whole new set of questions

Rasta Monsta · Rasta Monsta's Garage

Pull the rad and have it flow tested. People tend to put the wrong coolant in these things, which is the express train to clogville.

DSPTurtle · 07-01-2008, 10:37 AM

Quick update... ran both days at Sebring this past weekend. Car ran great. Used a lot of oil (2 quarts over the 2 days) but only creeped into the yellow zone towards the end of the last day when I graduated up a group and had to run much sooner then usual.
I don't know if it was the t-stat replacement, the water wetter or the fact that I left the belly pan off the car... whatever it was worked like a champ though.
Next time around I think I may be able to leave well enough alone (other than an oil change).
Thanks for all the tips and tricks guys!!!

Rasta Monsta · Rasta Monsta's Garage

Yellow bad. You really should have that rad flow tested. Also, running with belly pan off DECREASES air flow through the radiator.

924Sman · 07-01-2008, 04:06 PM

No pan also creates lift under the hood and can also result in rocks/dirt to get up in there.

On the pan.... I had mine off and noticed my front end go light at hi speed, put it back on and that went away.

Dal

Spidey944 · 07-01-2008, 06:31 PM

OK, there are three pans, the "batwing", the black one in the center, and the metal one that protects the caster blocks from the exhaust heat. Which "pan" are you talking about causing lift?

924Sman · 07-01-2008, 07:21 PM

Quote:

Originally Posted by Spidey944

OK, there are three pans, the "batwing", the black one in the center, and the metal one that protects the caster blocks from the exhaust heat. Which "pan" are you talking about causing lift?

You are referring to a 951, the NA has only one belly pan so it is a moot question in this case. Yours has an entirely different undertray system. but thanks for getting that in there to kill any confusion!!

Dal

DSPTurtle · 07-02-2008, 07:24 AM

Well, up to 130 mph (sanctioned on a track) the car was rock solid. Since it was on a track there was not too much worry about rocks and dirt (that was my primary concern). From an Aero perspective, that pan is not sealed, nor does it have enough surface area to really make that much difference. Remember, these are little aluminum kick plates, not contoured under body belly pans designed to create aero downforce.
The rocks and dirt are the main concern, but since it does not cover the oil pan, the only protection you are really getting is for the belts.
But, there must have been a reason Porsche put it there.
By the way... if removing the pan forces air up under there (around the motor) then it must have an effect on cooling. If removing it cause lift... high pressure under the motor, then there must be some effect on the cooling of the engine. I have had so many problems with the cooling system on this car over the years that I hesitate to say that the factory knew what they were doing when they designed it. Today would be a much different story then 1982 (probably 1979)... it would be really cool to get a Porsche engineer of today to weigh in on the design robustness of a 30 year old car. Clearly that pan was an issue since they changed it almost immediately!!!

924Sman · 07-02-2008, 07:46 AM

Well all I can say is the pan is there for a reason and the car new did not run as hot as it is now, removing the pan is not the issue the issue is something else is not right and needs to be addressed. By removing the pan and solving the temps is just a band aid, the problem is still there.

The pan is for protection from water and other debree. The air flow under the car is a secondary benefit and does make a difference. You want the air to flow directly under the chassis without obstruction, meaning the firewall, air goes up and hits the back wall which
creates drag. If you look at the fins on the pan they are designed to create a vacuum as air passes the fins it pulls air from the engine and out with the flow, same principle as syphoning.

Air coming in through the rad is not all captured by the rad and the rest is caught up in the engine bay and needs to go somewhere so it gets forced down and out through the pan via vacuum induced air flow.

Dal

DSPTurtle · 07-02-2008, 08:52 AM

Good point... however, around town the motor runs at the 1/4 hot mark all day long. It is only when pushing it on the track that it is getting to the 3/4 mark and occassionally into the yellow field. All it took was running the back straight in 5th to get the temp to come down. Maybe that is how it was supposed to run? I flushed the rad and nothing came out. I flushed the whole system actually and nothing came out but clean water after draining coolant. Are there aux coolers that guys use in the spec racing?
Oh, and as for my pan, those fins have long since become dinged and dented so they probably don't contribute to the vacuum anymore. Remember the old beetles that had their fins backwards? Overheated constantly till someone figured out that the factory had made a boo boo