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]

PS; surprisingly thermostat removal was relatively easy; After two 10 mm bolts removed, I was able to gently pry the top up enough to fit a HF trim pulling tool that had just the right angle under it. Pop! out it shot!

[GeorgeRud]

If the piston in the thermostat moves, it should be working though I don't know what the positions should be. Show pics at room temp as well to compare.

Also, what size engine are you running? Anything over a 2.4 (or 2.7 if you drive gently) would require an additional front cooler or you may see elevated temps.

[porschetub]

What size engine are you running? ,do you have a good seal around your engine tin?,how quickly do you get temp showing on your gauge after cold start ?,I find mine warms up quickly as it should.
I haven't researched the thermostat operation however I know they are meant to be open around 180F,they don't fail very often but are a very important part in our engines.

[davebrossi]

Hi all;

It's a 3.2. Prior to dropping the engine, the engine ran at 210 without fail. Rubber seal around the engine is new.

[mepstein]

Oil pressure still the same?
What did you do when you dropped the engine?
Since it ran cool before, something changed.
Oil flow, air flow?

[rgalla9146]

Check you fan belt.

[porschetub]

Oil pressure still the same?

(IMG:style_emoticons/default/agree.gif) good question to ask Mark,mine got to over 200F once and the oil pressure dropped noticeably,I somehow think the OP will have much luck running a 3.2 without a second cooler up front,depends on how he has mounted the extra one he has now?
Had a look on the net appears that thermostat is opening fully ,a bit hard to tell though.
Perhaps other 3.2 owners running front coolers could add to this.

[mepstein]

Check you fan belt.

I was thinking that too. I would think the alternator light would go on but things happen.

[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!

[porschetub]

You did well @ answering all requested questions and have obviously done the hard yards jeez this makes little sense why had a great running engine before....then this???
Are you on stock motronic or on carbs by any chance ?

[davebrossi]

You did well @ answering all requested questions and have obviously done the hard yards jeez this makes little sense why had a great running engine before....then this???
Are you on stock motronic or on carbs by any chance ?

Stock fuel injection system (Motronic.)

[gms]

What size is the oil cooler and how is it plumbed?

[IronHillRestorations]

As I understand the thermostat should be fully open at 210. What kind of oil lines? I have seen braided stainless that had collapsed internally and was totally closed, but the hose looked fine

[davebrossi]

As I understand the thermostat should be fully open at 210. What kind of oil lines? I have seen braided stainless that had collapsed internally and was totally closed, but the hose looked fine

Hi Perry; they are braided stainless steel and that is a distinct possibility. In fact if the thermostat doesn't work out, that is my next point of focus. Looking at the design of the thermostat I keep thinking the large output should open completely at 210.

As for the plumbing of the oil lines the oil routes from tank to engine, engine to aux cooler and aux cooler over the top of the transaxle to the oil tank. The fan/aux cooler design implemented has a five years onwards development cycle. the testbed 914-6 with the installed aux cooler system has run without any instances of overheating in 100 degree plus summers in Dallas. Brad at 914 ltd did the install.

[gms]

bottom of thermostat should be open with heat


Oil cooler should be placed between scavenge return and tank

[gms]

Brad at 914 ltd did the install.

Should be no question about the installation if Brad did it

[Dave_Darling]

Is there any way the oil sump cover could have been installed the wrong way around? I don't remember if this is a potential issue with 3.2 motors, but with at least some 3.0s there is a way to install the sump cover backwards, and it causes oil pickup problems. Those can in some cases lead to overheating.

--DD

[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..

[forrestkhaag]

Sorta related experience on my Chris Craft twin Merc Mag 350 engined rocket / Under various conditions at sea, it would collapse one of the two seawater intake pipes after the surrounding motor cowling heated up / but not do so when cocktail cruising in Newport harbor. It turned out to be a failure of the fabrication of that particular length of rubber hose (unbraided of course) but possibly it is not your fault but rather, one of a faulty piece of hose.

In my 3.0 conversion, I used AN12 SS braided lines and thermal wrap on all line anywhere near the engine or headers, etc. No issues whatsoever and runs at 85 all day long as needed to compensate for the sale of the boat......... .

cheers