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

[davebrossi]

So after a gentle reminder, I figured I'd post some images of the aux oil cooling setup I use. The design comes from Rich Johnson and has been successfully utilized over a long period, though I imagine he had better control of the aux oil return line than I did. So! more pictures!

Here's an image of the fan;


The bracketing for installation;


And actual physical positioning on the car;





According to Rich; "This is a 72 plate cooler with fan kit from Latest Rage. Part number 117072"

[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.

[davebrossi]

Brief update; I've pulled the oil return line as I'm impatient and also because limited resources for line replacement mean it may take a while. A base 'test' of 'I run the line under a faucet to see if the pressure of water entering is the same as water leaving.' It is not. Bit of a delay and the rate of flow seems less on the back foot.

[davebrossi]

Well, if you'll permit me to resurrect this thread, I do have an update to report; I've replaced the Thermostat and O-ring with a new OEM unit, and at the same time I had the shop that made my original stainless steel braided line make a new one but reuse the fittings off the old. The result? Pretty much unchanged. At freeway speeds (out here it's 80 MPH) it doesn't take long for the temp to spike up to 240. A trip of about 15 miles and you're there. Just like before however, here's the kicker;

After pulling off and letting the car run at a slower speed, I switched on the Aux oil cooling fan, and lo and behold with some distance and gentle driving (I consider that nothing above 50 mph keeping the RPMs at less than 3500) the temperature went down. I now have a car that I can drive through town and never go above 215 with aux fan running. It's not 'fixed' but at least locally I can go out and about.

So to recap;
Thermostat is new, no change
Suspect oil line is changed, and secured above the exhaust header by no less than 1.75 inches.
I changed the rubber seal around the engine tin and I have left duct tape in place for the purposes of ruling it out only.
Oil in it now and filter have less than 200 miles on them.

The aux oil cooling system installed worked flawlessly until I dropped the motor, so I still wonder what on the top of the motor I could have disconnected to cause this. I'm still thinking there is something I missed.

[DaveO90s4]

Does your engine have an 'excess' pressure oil bypass valve to bypass the cooler under very high pressure situations - eg thick oil & cold starts? If so, and if malfunctioning, then possibly little of you oil is going via the cooler?

Is there a rag left somewhere?

[Justinp71]

A few thoughts I have after reading this-

-Is the new oil temp sender the same as the old one? Could it be possible the new sensor is incorrect? Something here seems to be the culprit to me.

-Did you pull off any of the air shrouding? could something be stuck between the cylinders and top cover?

-anything wrong with the aux cooler thermostat possibly?

-Did you change oil types? thicker oil will make for higher temps, but should change that high. What type of oil are you running btw?

Hope you get it fixed... (IMG:style_emoticons/default/drunk.gif)

[gereed75]

I'll mention this only because it has not been mentioned. I am not sure how timing is controlled on motronic, but advanced timing will definitely increase CHT which will increase oil temp. And maybe this is another variable that could have changed since engine ran cool

[earossi]

I'll mention this only because it has not been mentioned. I am not sure how timing is controlled on motronic, but advanced timing will definitely increase CHT which will increase oil temp. And maybe this is another variable that could have changed since engine ran cool

Unlike engines with distributors, the Motronic unit sets engine timing electronically. There is a high pressure regulator in the engine but it does not involve the aux cooler circuit.

[Jeff Hail]

Does this conversion have an 02 sensor. Going back at your photos I'm not seeing one or a bung anywhere. May be obscured by the exhaust?

I've seen some bad Mahle filters that did not flow. Try changing it out for another.

[earossi]

Does this conversion have an 02 sensor. Going back at your photos I'm not seeing one or a bung anywhere. May be obscured by the exhaust?

I've seen some bad Mahle filters that did not flow. Try changing it out for another.

The engine has a single O2 sensor tied to the DME.

We started out with a Mobil 1 oil filter; but in trying to address the over heating, we swapped it out for a Mahle which did nothing to address the oil temps.

I'm beginning to suspect the the oil always ran this hot and that was masked by a temp sensor that read low.

[Justinp71]

Does this conversion have an 02 sensor. Going back at your photos I'm not seeing one or a bung anywhere. May be obscured by the exhaust?

I've seen some bad Mahle filters that did not flow. Try changing it out for another.

The engine has a single O2 sensor tied to the DME.

We started out with a Mobil 1 oil filter; but in trying to address the over heating, we swapped it out for a Mahle which did nothing to address the oil temps.

I'm beginning to suspect the the oil always ran this hot and that was masked by a temp sensor that read low.

Is there an oil cooler on the motor and also an auxiliary one? If so it should be able to keep under 200f, per other 3.2s I've seen.

[GeorgeRud]

Two ideas, check that the fan is pulling air through the cooler and not trying to blow through the cooler. Also, could a second cooler be added on the driver's side of the transmission? If the one cooler drops it 50 degrees, another one should certainly bring the temps down to safe levels.

I'm a bit concerned that the air over the headers is quite warm (check your trunk floor after a summer drive), so eventually a front mounted cooler may be the best option.

[porschetub]

I'll mention this only because it has not been mentioned. I am not sure how timing is controlled on motronic, but advanced timing will definitely increase CHT which will increase oil temp. And maybe this is another variable that could have changed since engine ran cool

Motronic has most of that covered,never go's lean just rich if an issue,possibly issue with the distributor,is it firing on all 12 plugs ?,however my experience with early 3.1 so I could be well wrong.
The 914 gets more inward air than the 911 so this one is strange ,as asked has the OP lifted the fan shroud to check for crap around the cylinders,really important for good cooling.
The 964 is known to have oil leaks around the cylinders that could well cause lots of crap around the cylinders,just saying.

[earossi]

Thanks for all the replies. The 3.2 has an integral oil cooler that is controlled by a thermostat, which we just replaced. In addition to the engine cooler we have added an auxiliary external cooler with an electric fan which remains in operation via an on/off switch.

The 3.2 is a 6 spark plug engine.

[Justinp71]

Do you have the flaps on the under body of the car to lower the pressure under the engine so the air can exit from the motor? I know these make a bigger deal on the freeway than I would have thought. Someone might be able to post a picture of what I'm talking about, this was an issue on someone else's car.

Also do you have heat exchangers on your headers? There was a case where a guy had the inlets/outlets of the heat exchangers taped off and they basically were insulating the headers and making the car overheat.

[porschetub]

Thanks for all the replies. The 3.2 has an integral oil cooler that is controlled by a thermostat, which we just replaced. In addition to the engine cooler we have added an auxiliary external cooler with an electric fan which remains in operation via an on/off switch.

The 3.2 is a 6 spark plug engine.

Sorry yes had 3.6 in my head for some reason (IMG:style_emoticons/default/biggrin.gif) ,whats your cold oil pressure by the way ?,have you run a heat tester gun over the engine by any chance ?

[earossi]

Thanks for all the replies. The 3.2 has an integral oil cooler that is controlled by a thermostat, which we just replaced. In addition to the engine cooler we have added an auxiliary external cooler with an electric fan which remains in operation via an on/off switch.

The 3.2 is a 6 spark plug engine.

Sorry yes had 3.6 in my head for some reason (IMG:style_emoticons/default/biggrin.gif) ,whats your cold oil pressure by the way ?,have you run a heat tester gun over the engine by any chance ?

Cold oil pressure pegs the gauge at about 5 bars. Hot oil drops pressure down to about 3 bars. Those numbers are at about 2500-3000 rpm.

We did use an optical pyrometers to map out temps in the external plumbing and to determine how well the aux cooler was performing.

[Montreal914]

Oil temp sender needs to be matched with the gauge. I understand that you took measurement with the laser pointer but you still might want to check that.

On my /4, the thermocouple down the dipstick tube dipping in oil really gave me the feedback that I needed. I had the wrong sender (~+20 deg). It wasn't that clear with the laser pointer.

[davebrossi]

So the common repeating theme was 'whatever's gone wrong is going to be blindingly obvious when we figure it out.' Sure enough, while poking around I realized the fan belt has stretched over 6000 miles.. enough so that I can worryingly rotate the fan blades with one hand and a little force. Looks like we've found the culprit. Sadly this means dropping the motor again.. oh well, I'm pleased it's not 'you have a clog in one of the oil channels internal to the block' or something exotic. Fan belts, they're trixie.