Front Oil Cooler Not getting hot?

ZCAT3 · 07-29-2003, 10:50 PM

My 87 Carrera has been running a little hotter than I think it should. It actually seems to be fine under track conditions, but runs a little high under city and freeway driving. I removed the front cooler thermostat and tested it last year and it works. I also recently installed some of Chuck Moreland's finned oil ines. The odd thing I am seeing is that then temp gauge is getting about a needle width above the 90 degree celsius line (which should mean the thermostat is open) but the front cooler is not getting hot. The supply line to the cooler will be hot but not the return line? Any suggestions as to where I should look?

jluetjen · jluetjen's Garage

I believe that Sherlock Holmes pointed out that if you've eliminated all of the other suspects, that the butler may have done it.

In your case, what's the problem that you're trying to fix? How hot is "a little hotter than I think it should"? Under what conditions have you been seeing these temps? Have you considered that the heat is being radiated from Chuck's lines (as designed) and as a result the external cooler is sort of redundant in the situations that you noticed?

Wil Ferch · 07-30-2003, 05:02 AM

Whenever I've tested my system ( by hand) , you will notice that as the temp valve in the right/rear fender opens, the supply line to the front cooler will get *progressively* warmer on it's way to the front cooler. Meaning? It's warm to the touch at the thermostat, and the supply line "warm front" moves forward...in time...toward the front cooler. At some point, the front cooler itself gets hot ( just feel the front fender behind the headlight bucket !)...and then the return line gets hot too.

If the return line is still cold, either the hot oil is not reaching the front cooler or you have a blockage in the cooler itself...wouldn't you agree?

--Wil Ferch

Chuck Moreland · 07-30-2003, 08:19 AM

I'd like to say the return line is cold due to the finned oil lines dissipating heat, but it just doesn't work that way.

The supply side of the thermostat is always open, it's just a through pipe. The valve is on the return side only as in this picture:

The picture is desgined to illustrate finned oil line purge valve operation, but ignore that and just look at the thermostat diagram.

So the supply will always be hot near the thermostat, even if the thermostat has failed closed or the cooler is plugged up. Feel the supply oil line near the cooler to see if oil is truly flowing.

I suspect your thermostat is not opening, or perhaps opening just a bit and not fully.

ZCAT3 · 07-30-2003, 09:17 AM

Chuck - I think you are right. I had a problem with the T-stat not opening all the way last year and I pulled it out and cleaned it up and it worked again. Perhaps I should just replace the internal plunger T-stat mechanism at this point.

Chuck - do you know where I can get an internal mechanism that opens a little earlier - say 180 degrees?

Wil Ferch · 07-31-2003, 08:52 AM

The internal mechanism *already* opens up around that temp ( 182-189 degrees, or so, depending upon model year).

---Wil Ferch