New To Me 1987 924S Arrived

[River19]

Again, really appreciate the support here and my crash course in German engineered hydro-dynamics lol

I grabbed some premixed coolant this morning. I noticed when the car was cold (overnight) the expansion tank was pretty dry, below min line so I added some......worst case it blows out the overflow tube.

I took the car around the block, which in a 5 min drive is more than enough to get my needle into the red.

When I came back, with he car still running I cracked the 12mm open and sure enough there was sputtering, steam, some splashes etc. I let that do it's thing for several minutes, rev'd the engine a bit as well etc. I never reached a point where I would say a "steady stream" was coming out but I was getting coolant out and of course then it just started steaming on the engine so I couldn't tell if steam was still coming out per se. So I gave the hose a little squeeze and tightened the 12mm and released the hose. Checked the temp gauge and it was still sitting solidly in the red.

A few observations and notes:
While I was letting things bleed, the heat was pumping in the cabin and the radiator fan was on.

I took new temp readings as well (ambient temp was ~35F); the top hose to the 12mm bolt was reading 155F. The bottom hose from radiator to pump was cool at ~60F; The hose from the expansion tank was also cool at ~60F. The block opposite the Porsche logo side was ~165-175F and the logo side was ~180-190F. Meanwhile the gauge was showing full red zone.

I wish I could post a video of the bleed screw action as it was as @Tom described, spurting drops of coolant and steam initially, then I think the steam was cause more from the coolant leaking out onto a warm motor vs. coming up out at an angle from the bleed screw.

I think I will need to repeat the heat cycle/bleed process a couple more times to get all the air out. If I do that and assuming I remove additional air from the system, and knowing the fan kicks on, the heater core appears to be operating as I get plenty of cabin heat........can we be reasonably sure the engine is actually cooling and perhaps it is a gauge or temp sending unit issue?

Do those temps appear out of whack?

Please and Thank you !!!!

[Tom]

Hard to say from that alone if--

--You still have air pockets --most likely

--Your thermostat is stuck -- possible

--Or your gauge is lying - less likely, especially if it smoothly climbs from the bottom of the gauge until in the red.

How much coolant did you add? Did you add any after opening the bleed screw? The last time I filled my coolant, it took nearly an extra gallon of coolant after the initial fill. I'd keep bleeding. If you have cooling system pressure tester, you can put 5-10 psi in the system and bleed it that way -- that tends to be more efficient. If not, I'd bleed it several more times before ruling out air as the root cause.

Also try pointing the IR gun right at where the gauge temp sensor screws into the block.

Are your fans kicking on?

Do you have a multimeter you are comfortable using to check resistance? We could rule out a faulty sender quickly that way...

[River19]

Hard to say from that alone if--

--You still have air pockets --most likely

--Your thermostat is stuck -- possible

--Or your gauge is lying - less likely, especially if it smoothly climbs from the bottom of the gauge until in the red.

How much coolant did you add? Did you add any after opening the bleed screw? The last time I filled my coolant, it took nearly an extra gallon of coolant after the initial fill. I'd keep bleeding. If you have cooling system pressure tester, you can put 5-10 psi in the system and bleed it that way -- that tends to be more efficient. If not, I'd bleed it several more times before ruling out air as the root cause.

Also try pointing the IR gun right at where the gauge temp sensor screws into the block.

Are your fans kicking on?

Do you have a multimeter you are comfortable using to check resistance? We could rule out a faulty sender quickly that way...

Thanks Tom.

Just did another round, got it up to temp (seemed like it took a touch longer to get to red) then cracked it open (even elevated the front of car a touch) and when cracking the 12mm I was greeted with more steam and sputtering, I let it go for a few mins until I couldn't stand the mess anymore.

I only added about 1/3 of a gallon or maybe 1/2.

No matter where I measure temp right now the highest I am getting is like 180-190F. I will look for where the temp sensor screws in and hit that the next time it is up to temp.

My multi meter was stolen so that is out for at least the next day or so.

Fan kicks on and off, meaning it isn't stuck on, it cycles as you would think. Meanwhile once it is in the red, it tends to stay there through my bleeding although I did notice it dropped from being in the red to a tick below as soon as I rolled the car back to flat ground from front end elevated. Not meaningfully so, but still.

I also notice the common "old car" electrical phenomenon that when I put my turn signal on the temp and fuel needles move, either in rhythm with the signal load or sporadically.

The car drives and behaves like nothing is out of the ordinary etc. with the exception of the temp gauge reading hot ...

I will try another round of bleed in the morning.

[Tom]

Hard to say from that alone if--

--You still have air pockets --most likely

--Your thermostat is stuck -- possible

--Or your gauge is lying - less likely, especially if it smoothly climbs from the bottom of the gauge until in the red.

How much coolant did you add? Did you add any after opening the bleed screw? The last time I filled my coolant, it took nearly an extra gallon of coolant after the initial fill. I'd keep bleeding. If you have cooling system pressure tester, you can put 5-10 psi in the system and bleed it that way -- that tends to be more efficient. If not, I'd bleed it several more times before ruling out air as the root cause.

Also try pointing the IR gun right at where the gauge temp sensor screws into the block.

Are your fans kicking on?

Do you have a multimeter you are comfortable using to check resistance? We could rule out a faulty sender quickly that way...

Thanks Tom.

Just did another round, got it up to temp (seemed like it took a touch longer to get to red) then cracked it open (even elevated the front of car a touch) and when cracking the 12mm I was greeted with more steam and sputtering, I let it go for a few mins until I couldn't stand the mess anymore.

I only added about 1/3 of a gallon or maybe 1/2.

No matter where I measure temp right now the highest I am getting is like 180-190F. I will look for where the temp sensor screws in and hit that the next time it is up to temp.

My multi meter was stolen so that is out for at least the next day or so.

Fan kicks on and off, meaning it isn't stuck on, it cycles as you would think. Meanwhile once it is in the red, it tends to stay there through my bleeding although I did notice it dropped from being in the red to a tick below as soon as I rolled the car back to flat ground from front end elevated. Not meaningfully so, but still.

I also notice the common "old car" electrical phenomenon that when I put my turn signal on the temp and fuel needles move, either in rhythm with the signal load or sporadically.

The car drives and behaves like nothing is out of the ordinary etc. with the exception of the temp gauge reading hot ...

I will try another round of bleed in the morning.

Sounds like you are making progress on bleeding out the air. If you added 1/3 to 1/2 gallon already, that means you had lots of air in the system. I'd bleed more and see if things keep improving. Like I said, I had to add nearly a gallon to my system recently even though it 'looked' full -- so you could still have lots of air (or not, hard to say). After bleeding it again, sit in the car and rev the motor to 3k for 10 seconds to see if the coolant temp drops quickly. If it does, that's a tell-tale sign of air in the system (still).

Sounds like you have some ground issues going on too, which could be causing your gauge to read higher than actual. It's a 944 rite of passage to go through the chassis ground points and clean them up, as well as the 'football' connectors on the back of the cluster. Sounds like your car is a prime candidate for that!

Don't suppose you have any resistors sitting around? If you had, for example, a 68 ohm resistor, you could pull the spade connector off the sender and connect it to ground through the resistor to see if the gauge produces the right temp for that resistance level (69.1ohms = 80c, first hash). Similarly, if you get a multimeter, you can check the resistance of the sender at ambient temps to confirm it's reading correctly.

Also, for what it's worth, it doesn't sound like the engine is truly overheating given the IR temps, but running it a long time with a dry/steam-filled head is still not a great idea -- so fingers crossed a little more bleeding will at least keep it under the red zone until you get it to the shop...

[River19]

Thanks @Tom

Tomorrow morning is another round of driving around the block to get it up to temp and making a mess with spurting coolant. I am also curious to see what the coolant level is in the reservoir after sitting all night as it was basically dry this morning.

One of the allures of the 924/944 for me was the ability to tinker and learn as there is no way I am "tinkering" on my 997 as that is intimidating, expensive and a wild PITA for access to things in comparison. So here I am trying to figure this crap out and at the very least I am taking a crash course in the coolant system.

BTW, I saw a video on the temp sensor replacement (trying to find the location) and it looks like it is on the front of the block under the throttle body and top coolant hose......is that the one that I should take a temp reading on with the IR gun?

Again appreciate all the support.

Morning Update:

Expansion tank was again low this morning, which makes sense if there were voids in the system. I checked and I had only added 1/4 gallon yesterday. I added about another 1/8 to 1/4 gallon and then I took it around the block for a heat cycle and it never approached the red but did warm up sufficiently. I performed another short bleed, some steam but seemed to be less vigorous than previous bleeds.

I did notice a decent sized puddle of coolant under the car but I believe that was from yesterday's bleed activity as I have not seen a puddle like that before (like if there were an obvious leak). So I put down fresh cardboard and went out for a another loop.

The car felt great and the temp stayed close to the middle of the gauge on my normal loop so I extended it for ~15-20miles total and I wasn't abusive but wasn't gentle either and the needled never approached the red. It stayed between half and 3/4 and mostly half and when it did approach 3/4 at either a light or while lightly cruising in 5th gear, it quickly returned close to halfway.

Short of a massive leak somewhere I believe we have mostly solved for my issues. I will see what the cardboard looks like tomorrow morning as well as the reservoir before I head out for the 45 mile trip to the shop. If the reservoir is low I will top off and head out.

Thank you @Tom for the help and hand holding as well as others with helpful suggestions.

(BTW, the car was a delight to drive.....so connected and balanced)

[River19]

Update 4/10/26:

Car has been at the shop this week and I spoke with them today. Overall, solid bill of health with a few things to address. Clearly we knew something was up with the cooling system and it looks like there was a leak at the heat valve, so they are taking care of that. The other item I had them look at was a vibration above 3500rpm and they suspected and confirmed the balance shaft belt wasn't timed correctly, I guess that is an easy thing for a non-experienced shop to get wrong (previous owner used a more general shop vs. a Porsche specific shop).

They also identified that when the previous shop replaced the water pump they did not replace the cam seals etc. and they are leaking as you would suspect.

So this round we will address the balance shaft, coolant system and a few other smaller things which will include tensioning the timing belt correctly to make sure everything is good to go with the proper tools etc. Then the plan is to drive it for the summer and then get it in for a major service in the Fall and address the seals etc.

They also thought the paint looked fantastic and with a solid detail etc. they can pull out a couple dings and the car will look pretty damn good.

I asked if I in his opinion I bought a decent starting point and he said the list of "to do" items is actually really short for a transaxle car and it was a really solid buy, so that makes me feel a little better, well that and I got my 997 out of my winter bubble storage and drove it 80 miles in the past couple days.

[944er]

One thing I learned when I replaced my radiator is that bleeding the system with the front elevated is really good for getting all the air out of the engine block. Unfortunately, this leaves the upper radiator hose and part of the radiator above the bleeder, and thus the system is not completely void of air. I now would suggest bleeding once with the front elevated, then bleeding again (and again...) with the car level.