Thermostat operation on a six conversion, Still trying to suss out the overheating issue, might be found? Options

[davebrossi]

I tried very hard to get my 914 to Parade, but no matter what we tried, I couldn't stop the motor from reaching temperatures of doom. While I did make it to Parade, the car did not. While there, the theory arose that maybe the thermostat on the 6 had stopped functioning correctly. I just pulled it, cleaned it up, and carried out a boiling test. Hoping someone might be able to tell me if it's functioning correctly or if this is the source of the obstruction to oil flow.

Also worth noting, the 'warm up' time it took to reach 210 was 15-30 minutes. Anyhow, picture time! (IMG:style_emoticons/default/piratenanner.gif)

The following four photos were at 'boiling' (212 at least)









At partial cool down (within five minutes of removing the thermostat from boiling water)







As an addendum; I have a laser thermometer so I had plenty of fun chasing after various temperature readings. I do not have the traditional 911 front mounted oil cooler (and the second thermostat associated with it) and opted for a simplified aux oil cooler with switch controlled electric fan. The difference in temp between oil entering and leaving the aux cooler is significant, I do not believe the car is unable to cool oil in normal conditions, but something changed when I dropped the motor. I've checked all the external oil lines and nothing appears wrong. No lines are touching the exhaust headers, and to test the theory that I had installed the engine rubber with gaps I made certain to seal every stretch off with high temp tape before a run. No change.

[davebrossi]

Hello everyone!

Well.. this thread sort of exploded quickly, so first off thank you so much for the suggestions! Let me summarize what led me to where I am now;

914-6 Conversion was carried out 4000 miles ago. At that time a 3.2 from an 88 Targa was installed with approximately 75k on the odometer. Compression checks were good, the motor itself was gone over, gaskets changed, etc. At that time, a Rich Johnson derived aux oil cooling system was installed. Sadly I'm not an engineer so the cool designs come from other people. The system relies on an aux oil cooler radiator and switch controlled blower motor, and for those four thousand miles, in every condition it's safe to drive a 914, the oil temp was always at or around 210F. The only exception was if I was low on oil.

4000 miles in and an oil leak has me so concerned I dropped the motor. the oil leak turns out to be a crush washer on the oil pressure sender, so with crush washers replaced, I reinstalled the motor. At that time I installed a new oil pressure sender unit, oil temp sender unit, and oil pressure warning sender as well as new crush washers. Wiring, breather lines, electrical connections and all are plugged back in. The car runs, but now it has an issue, after a very long amount of time to reach 210, it overheats. I never found the 'limit' because at 250 I cut the motor and sat in a potato field while I waited for it to cool down. I found that any freeway driving for prolonged periods (specifically an 80 MPH straight of about 15 miles) caused the temp to shoot up. Around town, and with the aux oil cooler fan running, I am fine.

So change of speed, that should mean the rubber seal around the motor is potentially bad? Well, turns out it was. Without heat exchangers the rubber is exposed to a great concentration of heat. Add the age of the material, and you can guess what I found. The side pieces of the seal were cracked and falling apart (the driver's side crumbled into pieces) and I replaced the rubber making certain it properly seals against the engine tin. So that part's taken care of. For the sake of testing, I also temporarily used duct tape to make sure there were no gaps. Still overheats.

Next, I checked the alternator (I was concerned about a different set of issues then overheating, but since the alternator belt was suggested I wanted to bring attention to it) and the fan belt is functioning properly. As is the alternator.

After this, I went back and reviewed the oil lines in and around the motor. Because I opted for a different setup from the traditional 911 (and 914-6) the car relies on only one thermostat, the main unit located right next to the oil pressure warning sender. Oil flows from the tank, to the motor, from the motor, to the Aux cooler, from the Aux cooler back to the oil tank. Lines all appear OK (I know, looks are deceiving, the next step after the thermostat will be to change the oil lines.)

I verified the oil temp sender is functioning as it should by using a Laser thermometer (these are awesome!) I also measured temperatures along each oil line. In the possibility that the aux oil cooler was clogged, damaged, etc I made a point of measuring temp going in and going out as well as the aux cooler itself. The Aux cooler removes a huge amount of heat! The Oil pressure sender is also registering correctly. When the motor is cool, I get 5 ATM with the throttle depressed, three at idle. Once the motor has reached the normal operating temperature range, the pressure at idle drops to 1, and with the throttle depressed 4-5 depending on engine load. Oil level is maybe a quarter of a quart low. At parade I got the pleasure of driving a 997 around and out of curiosity decided to look at its pressures out and about. Same Same!

Having gone back and asked myself the very valid question (what changed Dave!? Why dog, why?) I've looked at the oil tubes at the bottom (all OK) oil breather lines (all OK) the cooling fins on the jugs on the underside (I figured while I was down there, why not?) I've looked at the engine tin and it's new. It's also sealed as it should be. I've got a Mahle oil filter installed (strange but true, this does make a difference) and after consulting Brad at 914 Ltd and my dad (Ernie Rossi) we came to the idea that there has to be some kind of blockage in the oil system. Or rather they did. I just smiled and nodded because this is how I learn. Again, oil lines, or thermostat. So today, I pulled the thermostat.

Going through the build records of the car I noticed that the original O-ring was changed. The Thermostat was not. I carried out a boil test to obtain the images I posted above, but showing the thermostat at room temp should have been a given. You can tell unlike my dad, I'm no engineer. Here are the images of the Thermostat at room temp. That oily sheen is from Kroil. I mean, it's the magic spray!







So;
-Alternator belt is good
-No crushed fittings, Oil feed lines appear to be in-tact (suspect)
-motor was never dropped, forced, shoehorned or otherwise beat up while I had it out of the car.
-Rubber around the engine tin is new (By the way, everyone saying drop the motor to do this? they're right! (IMG:style_emoticons/default/headbang.gif) )
-Oil temp sender reads correctly (Verified by laser gun)
-Oil pressures currently measured are the same levels they were prior to dropping the motor.
-Oil cooling system functioned flawlessly for 4k miles. Other than disconnecting the feed lines from the aux oil cooler to drop the motor, the aux cooler was untouched. Functionality was verified by Laser gun (50 degrees shaved.)
-Oil tubes, all items that might have been crushed when I dropped the motor all appear in-tact visually.

Hopefully that addresses everyone's suggestions, and hopefully sheds some light on what's going on here. Open to suggestions!