928S4DUBAI

Will a faulty oil thermostat cause a 928 to run at high engine/water temps?

chris

dprantl

If you mean the one that regulates flow to the cooler, then yes it can. And it's not hard to replace during an oil change if you have the right size crow's foot wrench.

Dan
'91 928GT S/C 475hp/460lb.ft

928S4DUBAI

Yes Dan,thats the one do I replace individual components or a single unit?

chris

borland

It might be better to replace the oil pressure sensor with new one at the same time. Then you wouldn't need a crows foot to reinstall the oil regulator.

But the regulator does needs to be tightened with a torque wrench per WSM specified torque value, so as, to avoid leaks or damage to engine block.

borland

There are two springs that you could replace. The regulator insert is just a valve seat, nothing to wear, but may need cleaning/polishing.

dprantl

When I did mine, I replaced all of it. The two springs, seat, piston and crush washer (I think the usual 928 vendors sell a kit for this), and also replaced the sensor with a used one. My old sensor was gunked up since it receives pre-filtered oil.

Dan
'91 928GT S/C 475hp/460lb.ft

928S4DUBAI

thanks guys,will report my findings.

chris

Glenn Evans

Why do you suspect the oil thermostat? Are the hoses to the cooler relatively cool when the engine is hot?

Are both the fans coming on, and running at full speed? Is the bottom of the radiator as hot as the top? (If not, there is a lack or coolant circulation, and your water pump or coolant thermostat may be at fault.)

928S4DUBAI

Hi Glenn, new fans, thermostat,refurb rad,new water pump,new hoses and rad cap fitted.....not much left in the cooling department to replace.I don't have access to the car at the moment but intend to feel the pipes. It's 100F+ by 10am here in Dubai it pushes the temp beyond the comfort zone with gentle motoring and reduces the a/c output...think it has to be the oil stat/reg parts not performing.

chris

dr bob

Chris--

The reduced AC output may be a telltle that the fans aren't functioning adequately. The only thing common to AC and engine cooling is airflow. If everything goes cooler when you are beyond "gentle motoring" speed, look at the fans. With the removal for the radiator replacement, they would have been removed/replaced too. Easy enough to miss getting one fan connector attached for instance.

Glenn Evans

Chris,

What sort of coolant temperatures are you seeing? If you are in slow or stationary traffic at highish ambient temperatures, the engine will run warmer than it would if you were traveling at 45mph or more, or in cooler ambient temperatures. Is your gauge reading higher than it did previously in similar conditions?

Until MY89 or 90 (can't recall exactly), the oil "cooler" was a heat exchanger in the left side radiator tank. The later external tank, mounted in front of the radiator, doesn't look to get a lot of airflow from the fans (I could be wrong there). So neither type of oil cooler provide much cooling when stationary or at low speeds, so I doubt that oil not flowing through the cooler when in traffic will cause the engine to overheat.

If you spend a lot of time in traffic at high ambient temperatures, you could remove the belly pan. Its main benefit is the reduction of drag at highway speeds. Its removal will improve the airflow past the other oil cooler (the sump) and its radiation of heat.

cfc928gt

Chris, my '89GT ran cooler after I replaced my failed oil thermostat. The GT had it's radiator replaced at 40k miles with a Devek aluminum one by the PO even though the original radiator was in perfect condition. It always ran past the last white line and on very hot days with the A/C on in traffic I got the first warning on two occations. After the oil thermostat was replace the car ran cooler and I never had another overheating problem. I suspect the OP replaced the radiator chasing down a cooling problem that could have been solved by simply replacing the oil thermostat.

928S4DUBAI

I have been chasing this problem for a while now; I have had my car for over 5 years now, it has always run on the warm side then I had no2 fan fuse blowing in a big way.. the correct fuse melting on several occasions. I purchased replacement fans from 928 specialists a while back but only just got round to fitting them.There is no change to the previous condition the no2 keeps blowing.
Temps a year ago were mid 80's to 90 moving or in traffic but lately 90 to the top of the scale! I have to fix this as I have sold the car to my daughters boyfriend. I know how good this car can be and I want Phil to enjoy Porsche's finest the way I have. (I also have a 65 911 ;in my possession for 30 years so I bat for both sides!)
I am putting my faith in a new thermostat assembly,filter and a few litres of mobil 1.
Thanks for all your help.

Let you know the results!

chris

PHIL928

Hey guys
Thanks for the help!
I was on the verge of buying a new radiator and this seems like such a cheap and easy fix!
Chris thanks for starting this post, I really appreciate it!
I'm truly glad I bought this car, it's been awesome to drive so far, and fixing this overheating problem would make it much nicer :P
I can't believe how undervalued this car is, my dad has an M5 and I think he is a bit jealous of my shark :P

Yeh I'll post the results on here within the next couple of weeks.