Coolant Leak When Refilling System

[EuroFighter2003]

Hello All,

I have an issue that really stumps me, and I am hoping some of you may have some knowledge on where to look from here. Last night I had a coolant leak after refilling the system (after a couple of cooling system flushes with distilled water). When refilling the block via the upper radiator hose (as Clark's garage suggestes), I get a coolant dump once the liquid reaches a certain level in the block. And I mean A LOT of fluid leaks out of the system, not a small gradual leak. Keep in mind that this is leak before I get coolant spilling out of the bleed screw (indicating that the block is full).

However, when pressure testing the sytem overnight, I didn't get any leakage, and the system held 8-10 psi overnight. Any ideas what might have caused such a leak when refilling the system? If it was leaking out of the water pump, I would imagine that it would have shown some signs of leakage when pressure testing the system.

Also, do 944 pumps have a weep hole? I have searched online, but have not found anything definitive.

Any advise on further troubleshooting would be greatly appreciated. I am hoping that the pump or pump seal didn't go bad, as they are only slightly over a year old.

[walfreyydo]

Could it be that the system was holding pressure due to the closed thermostat? Once thermostat opens then you have coolant flowing to all parts of the engine, likely where your leak is located.

There are a limited number of locations where you can have a coolant leak, so where is it coming from? Its either the hoses/hose connections, the radiator, the oil water separator, or the seal on the pump.

Secondly, I never fill coolant through the upper radiator hose. I add it to the coolant tank with the bleed screw cracked, tank cap off and the car running, making sure that as the coolant level decreases (as it continues to circulate through the engine once the thermostat opens) I am adding more coolant. Once coolant starts to flow out the breather screw (with no air), I close the bleeder, turn off the car and ensure the coolant level is within the marks on the tank, if needed, top off.

Ive used this method probably a half dozen times and have never had an issue with air pockets or anything. If you fill it through the upper radiator hose there is no way for you to know if you are adding too much (maybe you are over filling?), whereas the coolant tank has actual lines for max and min that you can keep an eye on as you go through the bleeding process.

[EuroFighter2003]

There are a limited number of locations where you can have a coolant leak, so where is it coming from? Its either the hoses/hose connections, the radiator, the oil water separator, or the seal on the pump.

Thanks for narrowing down the list of places where a leak might occur. I have so far checked that it is not any of the hoses, and based off the leak location, I doubt the radiator is the offender. Pressure test last night did not reveal any leakage at all, might do another test later tonight to confirm.

Secondly, I never fill coolant through the upper radiator hose. I add it to the coolant tank with the bleed screw cracked, tank cap off and the car running, making sure that as the coolant level decreases (as it continues to circulate through the engine once the thermostat opens) I am adding more coolant. Once coolant starts to flow out the breather screw (with no air), I close the bleeder, turn off the car and ensure the coolant level is within the marks on the tank, if needed, top off.

My only concern with using the method described above is that I fully drained the system (both the block and radiator together). I was following the instructions posted on Clark's Garage as closely as possible. If I were to "overfill" the system, I would assume that the excess would leak out of the bleed screw on the top of the engine, and not other parts of the system. But I also am pretty new to these cars, and this is my first time messing with the cooling system so I may just be missing something.

[jeyjey]

If you're filling through the upper radiator hose, then the other end of that hose is disconnected from the radiator, right? Any chance it was spilling out there?

[EuroFighter2003]

If you're filling through the upper radiator hose, then the other end of that hose is disconnected from the radiator, right? Any chance it was spilling out there?

Potentially, but I thought that this section of the system was isolated when refilling the block only. I think the best plan would be to set up a camera later tonight under the car to see where the leak is originating from. I plan on doing one last flush and refill.

[danmartinic]

Though I believe the bleed screw is on the other side of the thermostat from the hose you're filling, perhaps your thermostat is letting coolant by.. it's coming out of the bleed screw without you noticing.. and dripping on the floor

I assume you're holding the hose above the bleed screw

[jeyjey]

Potentially, but I thought that this section of the system was isolated when refilling the block only.

The thermostat's job is to redirect much of the coolant flow to the bypass loop during warm-up. It's not necessarily water-tight.

[zooklm1]

I had a problem once where when I installed the upper radiator hose it stuck out a little too far and when the fan came on, it clipped a small hole into the hose. The pre-start bleeding of air was all good and initial no leaks until there was one. This was on an 86 944 turbo. Mot sure if it is applicable to your situation but thought it might help someone.
Lee

[whalenlg]

I had a problem once where when I installed the upper radiator hose it stuck out a little too far and when the fan came on, it clipped a small hole into the hose. The pre-start bleeding of air was all good and initial no leaks until there was one. This was on an 86 944 turbo. Mot sure if it is applicable to your situation but thought it might help someone.
Lee

Same. Turned out the new hose was a wee bit longer than it should've been.

[BennSport]

I had a problem once where when I installed the upper radiator hose it stuck out a little too far and when the fan came on, it clipped a small hole into the hose. The pre-start bleeding of air was all good and initial no leaks until there was one. This was on an 86 944 turbo. Mot sure if it is applicable to your situation but thought it might help someone.
Lee

Same thing for me! The alternator pulley had sheared a huge gash in the hose draining most of my coolant I ended up trimming a new hose and upturning it away from the alternator