AD7TCAR

My oil lines to the front cooler on my 87 Carrera don't get hot, even when temp gauge reaches mid-way, or about 221F. The going line gets hot/warm a couple of feet past the external tstat, but I feel like that is from temp transfer from the tstat body, not flowing oil. How successful are tstat rebuilds? I have heard conflicting opinions. My local guy will not rebuild them. Some one said only about 1 in 4 attempts is successful. Is that because you can't get them apart? Seems as if you replace internal parts properly the unit should work.

Summer in Mississippi can be brutal, and it's getting warm already. I want to fix it ASAP. Any suggestions will be greatly appreciated!
Thanks For The Help!
Tim

Jeff Curtis

Tim, how long have you had the car? Does it ever get past the 9 o'clock position on your temp. gauge??

My suggestion would be to pick a warm day and leave it running or drive it through traffic for awhile and feel the lines through the front wheel well.

I used to check mine periodically on my SC...because I was always paranoid of something not working correctly with the cooling system. There was never anything wrong, but it seemed I had to wait a bit for the car to get heated up enough to flow oil up into the cooler.

If you still think you're having problems, it might be as simple as removing the thermostat and having everything flushed out. I've heard of trash getting in there from broken rings, etc.

Hopefully that hasn't happened to you...but it's possible that this stuff can sneak past the screen on the scavenge pump...I've seen it!

AD7TCAR

Good advice. I don't want to spend $350 plus half a day if I don't need to. 9 0clock would be 105C on the gauge or 221 F, and I've been there numerous times although not much above that. I think the tstat is supposed to open at around 180F or so?
Since it's not a daily driver, I think I'll try to take off the tstat, and if I can get those caps off, clean it out and try it again. (John Walker said if you can get them apart and re-do them, he doesn't see why they wouldn't work, although he replaces them, himself.)
Like you say, it may be clogged or fouled. ( I hope not with the precious insides of my engine!)
By the way, I've had the car about 17 months, and about 7k miles.
Regards,
Tim
Tim

Viv Offord

I've got the same problem on a '85 Carrera. The 'stat is very difficult to get apart. After welding up a tool to grip those large slot headed screws that cover the pressure relief valve and thermostat and then breaking the tool I gave up and took the car to a garage.

Unfortunately the garage could only get the thermostat cover off to change that part and that hasn't cured the problem.

I think the pressure relief valve is an important part in controlling the flow to the front oil rad as the thermostat part only allows the incoming hot oil to flow to the rad or not. In other words the pressure relief valve is the bypass to maintain flow back to the engine when the thermostat is in the cold position. Otherwise hot oil wouldn't get to the thermostat housing in the first place.

Well that's my theory gained from looking at the parts and from the fact that its still not working properly! I reckon the pressure relief valve is jammed open, diverting oil back to the engine regardless of the actual thermostat position.

AD7TCAR

Thanks, Viv. I am learning that this is maybe something I don't really want to tackle! I really appreciate all the responses to my query. Atleast I will be making a decision on a situation I have been informed about. (Surely some one has been succesful in a rebuild, as all the intenal parts are sold separately.)
Regards,
Tim

Jeff Curtis

Tim, I forgot to mention that I don't think your car is getting that hot. From memory, I think the thermostat opens a bit higher than 180 deg. - as that is a common standard for water cooled cars.

I believe it's around 230 deg?? I may be dead wrong, I'll try to look it up tonight in my Bentley manual.

Either way, the 9 o'clock position on the temp. gauge isn't that hot at all, the third tick mark on the gauge is a start!

You have a thermostatically controlled fan on your oil cooler correct? Can't remember if that was standard in '87 or not?

...if so, does your fan cycle at all on hot days?? Mine rarely came on unless I was at an autocross or DE. I had a Carrera oil cooler/fan setup from an '87, I believe on my '82 SC.

It's hard to diagnose being this far away! I would bet if you wait for a nice warm day, and drive through traffic a bit, etc. that your fan will cycle...that would prove that hot oil is getting up there.

I've witnessed two people chase this "problem" to death, only to find out that everything was fine...their car just wasn't getting hot enough!!

AD7TCAR

Hi Jeff. Thanks for your interest. If I understand correctly, the 4 tempmarks are 60, 90, 120, and 150C. 9 oclock would be 105C or 221F. 2/3's of the way between the 2nd and 3rd marks would be 110C, or 230F. I have been there with no oil getting to the front cooler. That's getting pretty hot.
I also have a Bentley manual for the 84-89 models, Bentley Stock # P989, and it has some bizarre info in it. I. E. on page 170-14, it says that the fan on the front cooler comes on at oil temp of 188 C or 370 F! A little late, wouldn't you say? (Gotta be a mistake!)
At the top of page 170-4, there is a somewhat confusing description of how the TStat/PRV works. It basically says returning oil temp of 113 F controls the operation of the tsat valve. (If it isn't working, there is no going or returning oil!)
I know I read somewhere the thing is supposed to open at somewhere under 200F. Heck, the internal tstat doesn't let oil go through the engine mounted oil cooler until 176F.
I'm still somewhat confused!
Again, thanks for everyone's interest and help.
Tim

AD7TCAR

Jeff: Forgot to add that yes, I believe the fan started on the 87's, and no, to my knowledge, it's never come on.
Tim