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.

[earossi]

Well, it appears my son has done a good job representing the overheating issues with our 3.2 motor.

I was able to ride in the car and had a visual inspection of the engine while I was in Idaho to pick up my son for our trip to the PCA Parade in Spokane.

There are two potential concerns. First, I found that when Dave re-installed the motor, one of the oil line mounting clamps was out of position. As a consequence, the oil return line from the cooler to the oil tank was laying in contact with the exhaust header. As pointed out by a previous poster, the line, visually, appears fine. It is a braided stainless steel covered line. But, I suspect that the line may have collapsed from the heat.

The second item of note is that the engine takes a very long time to reach temperature. From a cold startup, my guess is that it took 20-25 minutes for the temp gauge to reach 210. Ambient temps at that time were in the high 80's. This anomaly suggests, to me, that the engine thermostat may be frozen partially open. Rather than mess with it other then the temp test Dave performed, we have elected to replace the thermostat which we believe may be original. It will be interesting to see how long the oil takes to heat up with a replacement thermostat.

If the thermostat does not solve the overheating, we'll go ahead and drop the suspect oil line that was found to be in contact with the exhaust header.

Thanks for all the input from the group.

Lastly, I provided Dave with specs and pictures of the aux cooler installation, which he plans on sharing with this forum. It is really slick. Being rear mounted, it does not require the routing of oil lines to the front of the car; nor, does it require that you butcher the front trunk for the cooler installation. Cost of the cooler is about $150 plus installation and fabrication of appropriate oil lines, The cooler has an electric fan that can be triggered off a thermal switch or manually, as we chose to do..

[infraredcalvin]

one of the oil line mounting clamps was out of position.

Could this be a result of swapped oil lines?

Also, have you ever performed an oil change since you've owned? Are you using the same weight oil as previously? Are you positive you've got enough oil in the system?

[earossi]

one of the oil line mounting clamps was out of position.

Could this be a result of swapped oil lines?

Also, have you ever performed an oil change since you've owned? Are you using the same weight oil as previously? Are you positive you've got enough oil in the system?

Good questions. The hose design doesn't lend itself to a mixup. They are different lengths and the return line to the tank is the only one that is covered with a woven stainless steel cover.

The oil had been changed at least three times since the installation 4000 miles ago. We are running Mobil 1 20W50 which I have run in all of my other 911's.

First step is to swap out the thermostat next week. If that doesn't cure the problem, the next step will be to replace the suspect oil line. Based on what we have learned so far, I'm thinking the oil line is the culprit.