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Oil Pressure and overheating problems

My problem child is a '84 944. I just replaced the oil cooler seals, the oil cooler, the housing, the oil pressure sending unit, the thermostat, hoses, the radiator, and the thermoswitch for the radiators. The thermostat is OEM - 83 degrees C, the thermoswitch is a 75 degree C. I seem to have traded a LOT of oil leaks for an over heating problem. Here are the symptoms.

Temp gauge at the 3/4 mark or above
Fans come on above 3/4 mark - more like in the bottom of yellow
lower Hose cool
radiator cool

I bled the system, and only get coolant out of the bleeder - no bubbles. The system took over two gallons of coolant My guess is that the new thermostat isn't opening. Although it is new, I think it is the problem - any thoughts? Also, if I change to a cooler thermostat, any ideas about what temp, size, part number?

But I am getting ahead of myself. Shortly after the oil cooler seal, etc, my oil pressure read ok (4-5 until warm, 3-4 on highway, higher at load). Then, I hit a pothole, and the oil pressure gauge danced around abit and has finally settled on "0". I checked the leads on the oil pressure sender, and they are tight. Could I have a crappy sender and a thermostat? Seems unlikely - any educated guesses? - Thanks

Old 11-16-2004, 06:50 PM
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STOP DRIVING THE CAR.

FIrst thing you need to so is confirm that you have oil pressure. Since you just redid your oil cooler seals, you may have installed something incorrectly - like the oil pressure relief valve.

To check your sender, reverse the wiring, the gauge should peg at 5. If not, you may have a faulty sender.

I would suspect for the temp problem, that you have a thermostat problem. Did you install all fo teh seals\washers, etc?

You can get a lower temp thermostat at any auto parts store - it is the same thermostat that went into a lot of 80's VW cars.

Same rules apply to the thermo-switch.

AFJuvat
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Old 11-16-2004, 07:01 PM
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The thermostat came with the rubber seal that fits around the outter lip of the thermostat. I replaced all the pieces that came out with new pieces - the rubber ring that fits around the lip of the thermostat was all that was used. The box had a large "o" ring as well, but one didn't come out, so I figured that it was for another application. Yes, the snap ring is a pain. Any ideas what temp and what size I should look for? Does anyone else have a part numer (NAPA, etc) that will work?

The oil pressure relief valve went in pretty straight forward. I put it in place before tightening down the housing. Once everything was tightened, it slid in and out smoothly. I was gettting normal oil pressures before the aforementioned pothole, so I am reasonably sure the oil pressure is ok. Also, no lifter chatter or rod or main bearing thump (yet). I will heed your advice and verify Oil Pressure, though, before it gets on the road again.
Old 11-16-2004, 07:13 PM
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Cool

2 gallons of anti freeze is quite a bit of over kill. anti freeze leaks where water won't.
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Old 11-16-2004, 07:14 PM
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Also, I get no movement on the oil pressure gauge at all, even when I start the enigne from dead cold.
Old 11-16-2004, 07:22 PM
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I am using 50/50 antifreeze/water
Old 11-16-2004, 07:26 PM
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I know one is available that is 10 degrees C colder from Napa.

Don't remember a part number. Just ask - think it is a 84 - 86 deg C

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Old 11-16-2004, 08:03 PM
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If the thermo switch is 75 degrees and the T-stat is 83 degrees how is the car going to get hot enought to open the t-stat???? The fans will come on way before the temp is correct to open the T-stat. Am I just being stupid (its been a long long day)
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Old 11-16-2004, 08:03 PM
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thermostat will open because it is subject to the water that is inside the block. i am wondering if the thermostat isn't in there backwards...
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Old 11-16-2004, 08:23 PM
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I don't think you're stupid. I thought of this as well (maybe I am stupid too) but it seem that this set up is talked about on these threads. I assume that the fans will run all the time around time, but will shut off on the highway. The forced air at speed should take the radiator temp below 75C.
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Old 11-16-2004, 08:24 PM
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Thermostat is not in there backwards - I double checked before I put it in. Spring goes toward the pump...
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Old 11-16-2004, 08:26 PM
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i think afjuvat is correct.
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Old 11-16-2004, 08:45 PM
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Coleman, did you check the tightness of the oil lpressure relief valve? It could have "popped" out of its proper seating when you hit the pothole. Also, did you ever find the cause to that leak you mentioned during the test drive?

As far as the overheating goes, its really pointing towards a thermostat issue. Its not out of the realm of possibility that you picked up a garbage one. I've heard of this happening before. This is further supported by the hoses being cool after driving.
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Old 11-17-2004, 05:47 AM
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ColeLauterbach:

Just some thoughts:
-for your oil pressure problem, your service shop should have a mechanical oil pressure gauge, ( if they do not, but a cheap gauge from an auto supply store )use that first to check pressure, if you have pressure on that gauge, then it is an electrical not an engine problem (as in NOT terminal!)

-if you have put in a lot of coolant, have you checked your oil level ? if it has risen, or the oil has gone "milky", you have glycol in the oil....this is BAD !

-for your overheating, have you checked the temp gauge sender? Other than the temp gauge reading high, what makes you think it is overheating? Turn the heater control to full hot - does it blow hot air, are the heater hoses hot? If the engine really is running hot, and the upper and lower hoses are cool, that means there is no flow, and the first thing I would check is the thermostat - like Panzer909 said. Try running the engine, and putting a thermometer in the rad cap opening.....

-if none of the above provide an answer, I would start looking for something plugging the system.....example - when you installed new hoses, are you sure there was not anything inside the hose?........go ahead and laugh, I have seen it happen...............

Last edited by GUMBALL; 11-17-2004 at 02:58 PM..
Old 11-17-2004, 02:49 PM
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Hmm, the fans do come on though?...
Interesting, if the fans come on, then you're getting coolant flow, and warm coolant is getting to the thermotime switch on the radiator.

This is a little bit puzzling.
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Old 11-17-2004, 05:15 PM
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Thought #1...You might have multiple component failures. I hate troubleshooting these. Pull your thermostat and dump into boiling water and make sure it opens. Do you have a new radiator or did you replace it with a used one? When was your water pump last replaced?

Thought #2...electrical system problem. Yeah I know, there doesn't seem to be any connection, but I've seen a few really strange problems due to a blown fuse or a corroded ground. If you have several bad grounds (either open circuit, a short, or high resistance due to corrosion) then you could get no oil P indication and high engine temp indication and/or an erratic running fan. I suggest you check all of your fuses and reseat your relays. Pull all of your engine compartment grounds, sand them a bit with 220 grit, and reseat them. Don't forget the engine-block-to-chassis ground and the battery ground cable. The loss of oil pressure over the pot hole sounds like a broken wire.

Good luck and keep us updated.
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Old 11-17-2004, 05:55 PM
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Fear is a good thing. It usually keeps you from hurting yourself, or your Porsche. Today I drained all the oil and coolant. Oil nice and clean, considering it had only about 50 miles on it-no milkshake. Oil pressure sending nuts removed, cleaned, re-tightened. New thermostat - 83C. New 50/50 anitfreeze/water mix (the orange stuff - same as last time)

At start-up - low and behold - oil pressure (thank god). 5 at start up , 3 at idle.

However, after very little time temp gauge rose to just below the yellow. Bled it like crazy - seems like I would get clear coolant (no fuzz or sputters) and I would tighten it back up. Lower radiator hose remains cool, expansion tank remains cool, bottom of radiator cool, upper hose is hot, but not its-gonna-blow-any-second hot. At one point the top hose felt like it as under pressure, so I opend the bleeder. a little steam and then steady coolant - I tightened it back up, hose nice an soft.

Could it be that I am not bleeding this thing correctly? I even tried the mouth to mouth method, and got clear coolant from the bleeder.
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Old 11-17-2004, 06:31 PM
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Also - the radiator is new. I tested the thermostat in hot water - it opened nice and wide. When I pulled the bottom hose off to get the thermostat out, there was no question that the radiator was full of coolant, and it drained, so I don't thik there is a clog there.

I didn't check the hoses for any junk before I put them on. I really hope I don't have a bunch of packing peanut stuck in my head...
Old 11-17-2004, 06:34 PM
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This is a real melon scratcher indeed.

Looks like you licked the electrical issue on the oil pressure, now it's just the cooling problem.

Does the temperature ever get into the red area? (or is it yellow on the early cars?), or does it stay just shy?

How long did it take for the temp gauge to come up that high?...
I don't know if this is a useful comparison or not, but if I start my car on a warm day, it takes almost 15 minutes of idling before the temp gauge gets to it's normal position.

Seems to me the last tick on the temp gauge is 90-something degrees, it should never get that high under normal conditions.

I'm almost leaning towards an electrical issue on the temp gauge. Seems like a long shot, but if it only takes a minute or two to come up that high, then it's definately not that hot.

I'm trying to think of an alternative way to test whether the engine is indeed that hot, but nothing comes to mind.
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Old 11-17-2004, 06:49 PM
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I was thinking of installing an Autozone temp gauge just to see what it says. I think I can tap right into the threaded hole that the current temp sender sits in.

The temp came up to the yellow in about 5 - 10 minutes, maybe sooner. I wasn't really watching the time. I took it out an drove it a bit, and the needle stayed right on the edge of the yellow area.

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Old 11-17-2004, 07:14 PM
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