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(SOLVED) Magic coolant loss

NugMugs

NugMugs

New member
Joined
Apr 23, 2024
Hello, my 940SE has recently been having a problem where the coolant tank appears completely empty when the engine is running, with no visible leaks underneath the car. I have inspected all hoses, and there are no bends or leaks. I even bypassed the heater core just to be sure. The turbo seems to be whining a lot louder, although this doesn't seem to affect the performance at all. Could these issues be connected? I recently installed a new fuel pump and filter and performed a general tune-up. The car also has a new water pump. Any pointers in the right direction would be greatly appreciated.
 
Try pressure testing the system - had this problem on a Porsche 944 and it was a water pump gasket leak that was impossible to see. Also ensure you have no air in your system.
 
TilledChip said:
Try pressure testing the system - had this problem on a Porsche 944 and it was a water pump gasket leak that was impossible to see. Also ensure you have no air in your system.
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I second this. Air in the system can take a while to work itself out.

I've seen where a minuscule leak will evaporate before any coolant spreads. Pressure testing with a cold engine will reveal an external leak. Get underneath the car--use a mechanics mirror if you have to.
 
Allrounderco said:
I second this. Air in the system can take a while to work itself out.

I've seen where a minuscule leak will evaporate before any coolant spreads. Pressure testing with a cold engine will reveal an external leak. Get underneath the car--use a mechanics mirror if you have to.
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I'll get a pressure test done ASAP, thanks!
 
TilledChip said:
Try pressure testing the system - had this problem on a Porsche 944 and it was a water pump gasket leak that was impossible to see. Also ensure you have no air in your system.
Click to expand...
Didn't think the check that since the pump was replaced 6 months ago. Thanks!
 
A friends 90 245 had a sneaky head gasket leak. It would only leak under high speed driving. The damn thing passed compression and exhaust gas in the coolant tests. Finally used UV dye in the coolant and we could spot the dried trail of coolant coming from the back of the cylinder head down onto the bell housing. Try some UV dye in there and get the kit with the flashlight and glasses.
 
dl242gt said:
A friends 90 245 had a sneaky head gasket leak. It would only leak under high speed driving. The damn thing passed compression and exhaust gas in the coolant tests. Finally used UV dye in the coolant and we could spot the dried trail of coolant coming from the back of the cylinder head down onto the bell housing. Try some UV dye in there and get the kit with the flashlight and glasses.
Click to expand...
I guessed it would be something like that, but on a car with only 114k? It's been maintained well it's whole life. I've recently replaced the fuel pump, fuel filter, spark plugs, whole distributor, rebuilt the injectors, cleaned the throttle body and gasket, and crank position sensor, all OEM.
 
If the car was locally driven more than likely it probably got a lot of heat soak with the electric fan cycling a lot in hot weather. Hope the dye helps you figure it out. Don't forget to do the heater valve. There is a turbobricks thread with a replacement one that is cheaper.
 
dl242gt said:
If the car was locally driven more than likely it probably got a lot of heat soak with the electric fan cycling a lot in hot weather. Hope the dye helps you figure it out. Don't forget to do the heater valve. There is a turbobricks thread with a replacement one that is cheaper.
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Huh, does that happen normally or just the fact that it was the original gasket?
 
NugMugs said:
Huh, does that happen normally or just the fact that it was the original gasket?
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I will try to be more clear with what I mean. One of the things about an electric fan setup is that the fan has to react to a temp setting sensor and then the fan runs, cooling the engine. A mechanical fan is always moving air over the engine so the system doesn't have to react to heat building up and then running the fan, catching up to cool the temperature of the engine.

So, if a lot of that happens due to localized hot weather driving. I could see that wearing out a head gasket. Personally, every B230 I've had eventually needed a head gasket. Thankfully these are about the easiest car to do head gaskets on ever made. Not that it isn't a big job.
 
Hopefully you remedied the heater valve & hoses on the back side of the RB engine whilst the head was off? If not, you will be some day.
 
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