84 944 running warm & shaking

Tiny
944_RAD
  • MEMBER
  • 1984 PORSCHE
Hi folks, '84 Porsche 944 160K miles. Regular good maint. Since summer has arrived the car is now running at or slightly above the 3/4 mark on the temp gauge. When it does this it starts to idle rough. The tach remains constant however the car shakes at idle when it is hot. Thermostat recently replaced, the fan relay in the radiator is OK, fans engage at 80 cel. Thing is, it doesn't act up immediately after I change the oil. It does fine for about 100 miles, and then it starts shaking again. It has 10x40 oil. I have been told that it may need a bleed on the sealed cooling system, maybe a partial blockage somewhere in the cooling system, or it may be an idle adjustment thing. It is extremely expensive to go the 'trial and error' route. I am just looking for some input or guidance from folks who may have seen this type of symptom in the past. Thanks for you time. Rad
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Thursday, July 6th, 2006 AT 9:22 PM

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Tiny
944_RAD
  • MEMBER
As a follow-up. I took the car to two different professional shops and the second one made a diagnosis. They said that their external thermometers showed that there was not a clog in the coolant system. That they beat on the dash a bit and the gauge became unstuck, or adjusted itself down. (They didn't charge anything for this bit of insight ? ) The gauge still reads around 3/4, or a little less as things cool as winter sets in.

I did question them about the motor mounts and their collapse. They showed me how the original ones were full of fluid and would collapse but once collapsed then they don't generally degrade from there. I went ahead and had them replace both mounts with ones they said were solid rubber.

That helped with the rattle a little. What actually helped a lot was that they adjusted the idle a bit. So now it runs as it always has, which is smooth.

I have a sneaking suspicion that the O2 sensor may have something to do with something, or the DME going bad? Who knows?
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Saturday, September 9th, 2006 AT 9:08 PM
Tiny
KEN
  • ADMIN
Have you checked the car for a blown head gasket?
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Tuesday, September 12th, 2006 AT 6:42 PM
Tiny
944_RAD
  • MEMBER
Hi, Thanks for the question. Head gasket? I hope not. It burns no oil, so I hope that sign is that the head gasket is OK. Plus, one thing that the second shop did was to sell me a $20.00 radiator cap, so now it doesn't even lose any coolant. As far as I know, the thing is fine. Again, hopefully.

A guy was telling me that, in low profile engines, that the internal oil tubes are very small. So he suggested flushing the engine oil and switching to all synthetic. His rational was that synthetics flow easier and hold less heat. I wasn't sure that was all true and before switching over the oil I asked for a second opinion. The end result is that I did not flush the engine but did switch to a synthetic blend. And again, everything is fine with the motor for now.

There are several reasons that I didn't want to flush the engine. Primarily is the fear that I would throw off whatever homeostatic equilibrium or balance that is going on internally. (That sounds strange but.) If there are deposits in places inside of that motor, and it works fine, then those deposits should stay right where they are. I was worried that if I kept fooling with it that I would break something (oil pump, seals, etc.)
8)
Rad
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Tuesday, September 12th, 2006 AT 8:44 PM

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