New to Porsche - Advice Needed for 924S Overheating

[adamvuletich]

Hello all!

About a month ago, I purchased an '88 924 S and have been really enjoying it so far. I had been looking for a project car, and this guy really caught my attention. I am born and raised from Detroit - plenty of corvettes and mustangs rolling around already, so the uniqueness of the 924S caught my eye (I work for GM, so don't tell them I own this )


I bought it for a good price, and have fixed a lot of the issues it had with it (speedo cable, power window short, motor mounts, etc) but quickly started noticing that it had some overheating issues. To be honest, I am not sure if the issue has always been present, or if it is something that I caused since purchasing it. Maybe this is even normal.... I am used to the engine temp needle sticking straight up unless there is a dramatic problem.. This car seems to enjoy running at the third white line (the last line before the red zone) so I am concerned there is an issue. It might also be worth mentioning that driving at higher speeds seems to bring it down; that is, idling is when the temp will creep up.

Here is what I have done so far:

- Replaced the coolant with a generic dexcool coolant. It was sitting for a while, so I wanted to make sure there wasnt something wrong with what was in there.

- Replaced the expansion tank cap

- Replaced the water pump (URO brand). Had the front timing belt plastic cover off so can see that it is seemingly operating as it should. Also getting good heat in the cabin.

- Replaced the thermostat. As some forums forewarned, this sucked, especially since I didn't put it in when the water pump was out
After some reading, it seems like different water pumps seat the thermostats differently. There is a chance that my thermostat is not seated 100% properly. Could this cause an overheating issue? I have been assuming that this is a non issue.

- Replaced the upper and lower radiator hoses

- Ran 5 gallons of water through the radiator. It seemed to run through fine without any noticeable contaminates coming out with the water.

- Around the time that the thermostat opens, I can feel that the lower radiator hose is hot.

- I have tried bleeding this thing a lot. I understand this can be tricky for this car. I ran the car for about 45 minutes doing the 'ole tube and grease fitting over the bleeder valve trick and I still was seeing bubbles. I have it jacked up about a foot with the heater on full blast. I ended up calling it for the day and will try again tomorrow. Could my issues be because the car is truly that hard to bleed?

-I don't really understand how the cooling fans are supposed to operate on this car, but I am assuming this is fine. With early, late, 924, 944 models, it is hard to determine how the fans are supposed to operate. I disconnected the two leads from the switch and taped them together for testing. Based on my understanding, it seems like one fan runs when the car is off, and then both run at one speed when the car is "on" and same for when the ignition is running.

-I don't think I have a head gasket problem, but what do I know? I have not done a proper oil change yet, but the coolant drains fine, and oil on the dipstick seems normal.


Am I missing anything here? I would really like to get this addressed so that I can enjoy the few weeks left of nice weather before it has to sit in the garage over winter


These forums have been incredibly helpful, and in the end, I am learning a lot about how cars run, which was the main goal.

I appreciate any advice I can get!

AV

[Ernie944]

If you got heat in the car it mean that the thermostat is opening,if the fans doesn't come on it could be your Thermo fan switch which is acting up ...see pics no1 ,located on the left upper side of the rad see pic...btw thermo fans switch come in different degree.Hope this will help ,take care & let us know if any progress.

[Ernie944]

Clark's Garage Home Page Ok adamvuletchi I'm linking you to the site above ,it will greatly help you resolve any problems with your car in the future....once on site clic on the garage shop manual

[SilverLined]

Great advice, Ernie! Check for corrosion on those contacts, before replacing the switch.

[adamvuletich]

I appreciate the replies! So I just want to clarify, the fans do kick on, around the third white line at one speed. Is it supposed to have another speed? If it is, how do I know if I am seeing a high speed vs low speed? The only time I see something other than the one speed at the third white line is if the car is off, and the drivers side will continue to spin for a bit.

Might also be worth mentioning that when the the fans kick on for the first time, the engine temp will cool to around half way... then hover for a minute or two, then climb right back up to the third line. When the fans kick on for the second time, it seems as if the fans do not do enough to bring the temp down, and will just hang out in the third line area.

[adamvuletich]

Oh also - I notice that both fans will run when I turn on the AC. I still experience the overheating problem when the AC is turned on the whole time (fans constantly running).

[adamvuletich]

Thanks for the advice Ernie. I think I lost one of my replies, but does the 924S have multiple fan speeds? Both fans of mine pop on when the car hits the third line, nothing before that. The fans bring the temp down for the first time (to the middle mark), but it will creep back up. When the fans turn on for the second time/cycle, it seems as though the fans are not able to help bring the temp down, so it will hover right at the third mark.

PS SilverLined, I was just looking at your project last night, it is looking excellent! I hope I can get mine to turn out as nice

[Ernie944]

Originally Posted by adamvuletich

Oh also - I notice that both fans will run when I turn on the AC. I still experience the overheating problem when the AC is turned on the whole time (fans constantly running).

Click on Clarks garagrage ,then on Shop manual ,then scroll down...to troubles shooting....TS2 Cooling system.Let me know how your doing

[SilverLined]

Originally Posted by adamvuletich

PS SilverLined, I was just looking at your project last night, it is looking excellent! I hope I can get mine to turn out as nice

Thanks Adam! Will stay tuned in to your progress, as well. I'm also new to Porsche, and am learning as I go. Thank goodness for these forums, and invaluable resources like Clark's garage... we'd be lost without the great community surrounding these cars!

[Ernie944]

Originally Posted by SilverLined

Thanks Adam! Will stay tuned in to your progress, as well. I'm also new to Porsche, and am learning as I go. Thank goodness for these forums, and invaluable resources like Clark's garage... we'd be lost without the great community surrounding these cars!

Thanks for your positive respond,if you guys wondering where the cooling fans resistor are ,here is pics of location ,bad corroded connections such has ....pic.... on them could cause fans problems .

[Ernie944]

One last comment,you guys like all the rest here migth think that I'm sending lot of pics but my way of thinking is that pics are sometime worth a thousand words,ex if you don't know where the wiper switch is on your new to you car & you hit pouring rain ,then you will stranded on the side of the road rigth?

[9FF]

Originally Posted by Ernie944

Thanks for your positive respond,if you guys wondering where the cooling fans resistor are ,here is pics of location...

Well I learnt something today, I always assumed those resistors were under the dash on a 924S same as the early cars.

[16again2009]

I have a 1988 924S and have the exact same problem. I'm wondering if the radiators in these cars were just to small from the factory. I think the radiator in the 944 with the same engine is bigger but I'm not sure.

[Ernie944]

Originally Posted by 9FF

Well I learnt something today, I always assumed those resistors were under the dash on a 924S same as the early cars.

For the older car 84 like Silverlined .no luck they are under the dash,but for Adam he won the lottothey are located as shown in the the first pics ,so 9ff you really didn't learn somethig new ,my badbut difficult when dealing with late & early car in the same post.FYI the resistor is the round ..thing ...that look like a speaker magnet with red & brown wires.

[adamvuletich]

Glad to hear I am not alone. After pondering on it some more, I am wondering if there is a bad ground. When I purchased the car, one of the first things I changed were updates to the lighting in the gauges. When I put it all back behind the steering wheel, I noticed the fuel level stopped working. Took some fishing around to realize that there is a ground on the fuel level gauge that wasn't tightened all the way. As soon as I tightened it and cleaned it up a bit, it instantly started working. I am beginning to wonder if the gauge is reading higher than it really is due to a bad connection. I suppose the only way I can find out it to either a) clean the contacts and see if I notice a difference or b) purchase a temp gun to see if it matches the gauge.

Ernie, definitely appreciate the pics. I have a lot to learn still. I looked through the clarks troubleshooting, and have one way or another looked at all of the issues they list with the exception of a head gasket problem, but I am thinking that is highly unlikely the issue.


PS, I was reading through the manual during the LED swap and found that there is a light bulb inside the ash tray (mine was burnt out)! Hopefully that random bit of information helps someone out there. I would have never known about it without happening to see it flipping through the book.

[Ernie944]

Originally Posted by 16again2009

I have a 1988 924S and have the exact same problem. I'm wondering if the radiators in these cars were just to small from the factory. I think the radiator in the 944 with the same engine is bigger but I'm not sure.

Your rad is the rigth size ,if flush & clean properly it should work just fine ,the only time you'll need a bigger one is if you race the car then it will be advisable to install one like in the pic,,,Here we go again

[TheSecondChris]

It sounds like there may be nothing wrong with your cooling system and that the cooling fan switch and more importantly the thermostat you installed operate at the higher range of the gauge scale. By "overheating" do you only mean that the temp gauge goes to the first line to the right of the center line? If so, that's not overheating - unless it keeps going past that mark even with the fans blowing.

At what part of the gauge is your thermostat opening? It sounds like you may have installed a thermostat that is opening later than you'd like. This could be because it's faulty, or you installed one with a higher temp rating.

[jjeffries]

That fan sensor lists for less than $20. John

[Ernie944]

Originally Posted by TheSecondChris

It sounds like there may be nothing wrong with your cooling system and that the cooling fan switch and more importantly the thermostat you installed operate at the higher range of the gauge scale. By "overheating" do you only mean that the temp gauge goes to the first line to the right of the center line? If so, that's not overheating - unless it keeps going past that mark even with the fans blowing.

At what part of the gauge is your thermostat opening? It sounds like you may have installed a thermostat that is opening later than you'd like. This could be because it's faulty, or you installed one with a higher temp rating.

Agree with you about the thermostat oparating at higher range temp, but you should always match both the thermostat & the thermo fan switch in the same temp range exp a good match will be 71*-75*.I did on my 944 & never had over heating problems

[adamvuletich]

Thanks everyone for the help! To clarify, by “overheating” I do in fact mean the third white line on my gauge, aka the next white line after the middle. The new thermostat is indeed I think about 3 degrees C higher than the one that was in there before. Can’t recall off the top of my head what it was. After a lot more research, and the comments on here, I am also starting to believe this is normal. I just found it odd that Porsche designed a temp gauge range that is designed to flirt with the red box. It never ends up getting there, but it stresses me out I must just be used to the ones that don’t move.

Really appreciate all the help! Closing this issue out in my mind as resolved!