High temp at DE - help

bdonally · 07-23-2005, 04:01 PM

I have noticed my oil temps have been bit higher than last year, driving on the street.
This weekend at a DE (air temp about 85-90) the oil temp has become increasingly hot (280F) to the point that I am less than comfortable.
It's a 84 Carrera, mildly tweaked, with the 28 row cooler.
Question is - can the thermostat fail gradually and restrict (without totally stopping) to flow to the cooler.
The lines and the cooler are hot, so I don't think th flow has stopped completely. There is plenty of air to the cooler - I removed a brake cooling duct and there is a straight shot the size of a fog light directly at the cooler.
If this is symptomatic of a t'stat, next question is whether in the absence of rebuild parts on a weekend, can it be jimmied to ensure flow to the cooler, at the expense of normal thermostat action?
While an upgraded cooler is likely a good idea, I don't think the problem at the moment is the cooler - it has been OK in the past at these temperatures.
Appreciate the input

bigchillcar · bigchillcar's Garage

get an infrared check of oil temps..maybe the sender needs replacing..
ryan

bdonally · 07-23-2005, 04:22 PM

Did that - in fact stuck a thermocouple ito the oil tank.
Gauge is accurate.

bigchillcar · bigchillcar's Garage

hmm..thinking out loud about things you've probably crossed off the list. using a 20w50 weight oil at least? fan belt loose? mixture way lean? if the thermostat is functioning properly, and you've never seen these oil temps before at these ambient temps/de driving..it's hard to say..what temps do you expect to see? in other words, how far off are you from normal? maybe that will provide a clue..
ryan

Grady Clay · 07-23-2005, 04:56 PM

For DE the “Rubbermaid Solution” will solve the problem.

Best,
Grady

bdonally · 07-23-2005, 07:18 PM

I appreciate the suggestion, but my specific problem has, I think, developed progressively, leading me to think about faulty thermostats.
I have dismantled the thermostat and shimmed it into the open position (very neat vale arrangement, btw) and I will see tomorrow what, if anything, changes.
BTW - I noticed a lot of vapor coming out of the oil tank filler - I had noticed it earlier but attributed it to the very hot oil. What are the most likely causes?

Early_S_Man · 07-23-2005, 07:24 PM

Bob,

Any chance of mice having access to the car ... to build nest on top of the cylinders or engine oil cooler? Wouldn't be the first time that has caused severe overheating!

Paulporsche · 07-23-2005, 07:41 PM

Bob,
Just a thought, it's been abnormally hot and humid here the last month (as well as just about everywhere else).

KTL · 07-23-2005, 09:23 PM

How clean is your engine? Seriously.

We had very high temps yesterday at our DE and not one of the cars in my group of friends ('77 w/ 3.2- not necessarily stock with two fender coolers, stock '89 Carrera, stock '86 Carrera, '79 SC w/Webers running lean and a loop cooler- hot but not in the red, my abnormally clean stock '87 Carrera, another stock '87 Carrera that ain't all that clean) had a problem with overheating. It was in the low 90's, humid and calm. Tough conditions and everybody was pushing their cars PLENTY hard. Other than the '79, everybody's temps were between the upper two white marks on the gauge. Probably in the 220-230 range?

Sounds like a thermostat problem (don't rule out the thermostat on the engine itself, but not too likely) or your engine mounted oil cooler could be kinda dirty too?

SCOTITUDE · 07-24-2005, 01:52 AM

Grady,
Whats the "Rubbermaid Solution"?

bdonally · 07-24-2005, 02:19 AM

Thanks for suggestions.
As I mentioned in my initial post - "high" is getting close to the red area - 135-140C, about 280F.

I'll see what happens today with the thermostat bypassed.

Elombard · 07-24-2005, 07:31 AM

DId you change the exhaust to a more restrictive by any chance? I hear 280 is too hot. Shouldnt you be shutting her down about 250?

Grady Clay · 07-24-2005, 09:02 AM

Here is the link

“Water vapor cooled 911 - the Rubbermaid Solution”

I'll put together a system and post pictures, instructions and a parts list.

Best,
Grady

bdonally · 07-24-2005, 11:58 AM

Thermostat bypass didn't solve problem.
There is a lot of blow-by, and I have several opinions that blow-by will put a lot of heat into the oil.
Sounds like I am not going tho be able to remian in denial about a tear-down.
Unless, of course, someone has a suggestion for a magic fix.

bigchillcar · bigchillcar's Garage

although it isn't an easy job with the engone still in the car, i suppose you could pull the engine oil cooler and the aux oil cooler as well and check for restrictions?
ryan

Grady Clay · 07-24-2005, 12:23 PM

Step zero.
Are there any symptoms other than running hot at the DE? Any noises? Mixture seem OK? Starts and runs properly?

Step one.
Cylinder leak test and cranking compression test. Do these several times with some driving in between to get good measurements. What do the spark plugs look like? How do the test numbers change if you add oil to a cylinder?

Step two.
Check sump magnets and cut the oil filter apart for inspection. You need to know if there is anything in the oil system.

Carry your AAA card and cell. If it slows or gets a new noise – STOP and call for a flatbed.

Please report what you find. Good luck.

Best,
Grady

bdonally · 09-05-2005, 06:58 AM

So far I have found the following:
-cyl 1,2,3 - comp ~ 115, leakdown 40%+ - cold, big air leak into oil tank
-cyl 4,5,6 - comp ~ 150, leakdown 3-5%

There is a big enough problem that I doubt that hot numbers will reveal too much, but I seek advice on that.

The big leakdown explains, I think, the hightemperatures. looking over records, the temp has been increasing over the past couple of years. I don't have any earler compression/leakdown info

Any ideas on why one bank would be consistently poor and the other consistently OK?

car has 140,000km, top-notch rebuild (for de/possible racing) at 75,000; has been on track for 20-25% of km since rebuild. Mods at that time include Autothority maf and chip, intake manifold ported, Al flywheel. Exhaust is stock other than some muffler mods, and no cat.

Any further testing ideas before removal?

Bob

kqw · 09-05-2005, 07:39 AM

Pull the fan and look on top of your engine. Clean off any debris/dirt/oil etc.

Make sure the cooling fins haven't shifted.

At that temp. your heater blower in the engine compartment should have activated. Did it?

What was your oil pressure cold vs. warm at 3K rpm's.

Are your oil lines going to the secondary oil cooler getting hot?

bdonally · 09-05-2005, 08:26 AM

All checked and OK.
I think the temp problem is caused by a great deal of blow-by - when how there is a srong stream of vapor coming out of the filler cap.
I am looking for some feedback about the left/right leakdown differences.

patkeefe · 09-05-2005, 08:38 AM

I just had the same thing at DE. I was running high oil temps. I yesterday checked my valve lash and changed the plugs. After inspecting the plugs, I was running so lean that the car couldn't help but run hot. I am in the process of richening the mix back up...PITA on the 78 CIS unit. Valve lash held their settings, at least, considering I pinned the tach a few times.
I also had to change the alternator, so while I was in there, I did check the tops of the barrels and heads as Warren suggested earlier (they were nice and clean), sprayed it all off with Simple Green, and stuck my pressure washer in there for good measure.