Serge944

When you don't restrict the the flow with a thermostat (at full open it only allows about 1/4 of the flow as an open water pump) the system doesn't pressurize properly and doesn't cool as efficiently once the engine has warmed up. More pressure = higher boiling point. Several 944 racers and I have noticed this trend.

Maybe if you ask me this question again next year, once I've learned more about thermodynamics, I'll be able to answer properly.

bjzorn

I had my rad replaced just recentl(Actually in Nov) because my gauge would go up to the bottom of the thrid line fans would come on and cool it down(This is when iding in traffic) still does it today I am going to try and replace th etemp sensor switch(You know the one that screws into the bottom of the rad) I will get back to you guys on what happens after I do this. MAybe check that too

Oh yeah and my car always sits below the second line when on the highway and slighty above it on touching when driving in the city

Brandon

Mark944na86

Hmmm. Interestingly theory, but I must admit I'm a bit skeptical. In a closed system, I'm not sure that restricting the flow would cause a pressure increase on one side of the restriction only. In an open system, sure. Now, the pressurised cooling system on our cars is not a perfect closed system (in a hydraulics sense) because there is still some air that can be compressed (in the reservoir), so in principle there is some capacity for a pressure differential in the system of the sort you describe to occur. But from a practical point of point, I would be surprised if such a pressure difference would be enough to make a difference to the cooling efficiency of the system at all.

But I could be wrong. Anyway, thanks for sharing your reasoning.

-Mark

Crackhead944S

My car too is running hot. At idle it will go to the third white line, then the fans kick in and goes downs to just over the second white line. I too have changed almost everything in the cooling system. Belts, WP, radiator, hoses, expansion tank, thermostat, coolant, bled with a pressure tester with the passenger side jacked up.....

I don't know what the problem is. Some people claim that this is normal, but none of my other cars' temp gauges move once they get up to temperature. Also, it has been so long since driving this car that it is tough to remember, but I believe, when I first bought this car, that once it got to just over the second white line it NEVER went higher/moved up or down.

Anyone?

Although the water pump was replaced with a "Porsche" rebuilt one that my mech got from a dealer, so I know that it could be the bad impellor.

I guess I should have done it myself. I was worried about messing up the T-belt.

KuHL 951

I think some people without thermostats have found that without this minor restriction the rate of flow increases in the loop and doesn't really spend as long in the radiator to cool down. This is more prevalent under load and hotter weather. Without a thermostat the radiator inlet/outlet temp differential becomes closer resulting in higher overall temps but not necessarilly overheating.

NICK G.

I don't know, tonight I gave it a drive but here in ST.LOUIS MO.it was 55 degrees here and I took it out for a drive and the hottest it got was below the 3rd mark under heavy driving but it had lots of fluctuation on the gauge like they say it should.The weird thing is it gets hotter as the days get hotter.I thought once you had the temp where it should be the weather would not affect it, like in a regular system.I mean I have a truck and a van that stay the same temp reading hot or cold out side.I have been pressure bleeding it every other day for a couple of days and I am not getting as much air out as I was.With every thing replaced how do you tell if the water pump is not functioning wright. NICK G.

Nasty Dash

I also have an early '85 and replaced WP, belts, rollers, thermostat, temp senders, etc., etc. and was still running hot. Fans would cylcle on/off once and then stay on.

Here's what I finally ended up doing.........

First: When I replaced the WP I got a NAPA 160 deg. thermostat and a 70 deg. celcius (158 deg. f) auxillary (radiator) fan switch thinking the temperatures would match. Didn't work. Ended up putting in a slightly hotter fan switch (83c) so the fans wouldn't kick on before the thermostat fully opened.

Secondly and probably most importantly was the bleeding... tried and tried.... finally ended up using the overfill/overflow method (Clark's Garage). Get the car at operating temp... heater on.. front end up high.. turn it off and then and fill the sucker up! I can tell there's no air because the upper hose is firm (not empty) and you can feel the backpressure when it's running when you squeeze it.

One more thought: you say the temp gauge is lower at night... Lights on? does your guage fluctuate when you turn the lights on/off? My oil pressure guage drops a hal bar when I turn the lights on

Damn those grounds!!!!!

Crackhead944S

I am going to check the grounds again. And, then I'm going to drive the hell out of it. If/when something breaks I'll let you know what was wrong. My wife, the CFO, says drive it. So, I said ok but we may need a new motor soon. She seemed to be fine with the risk, probably because she doesn't think there is any thing wrong.

Jeremy

Nick -

Any chance you have some illumination on the side of the gauge where your battery dummy light is? This was a sign that I had grounding issues on my early 944. It is just a soft red illumination that is only seen @ night - not as though the dummy light itself was on -

Jeremy