Fault - Cooling System and Overheating issue
#16
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So after letting the car sit a few days, I went to check and it is dripping coolant from the driver's side even when sitting and cold. Without the crazy removal of parts, I took out the engine bay fan and stuck my hand around a bit and sure enough the coolant tank seems to be leaking from the seam along the bottom of the tank. I'm concluding the tank has a fracture/crack. I also learned that the entire country has no Expansion Tanks in stock, they're in Germany and they won't be available until end of Feb/early March. Ouch - I just bought a used one off Ebay that belonged to a car with 13k miles, I'm hoping it'll hold until FCP gets the part. That said, I'm still trying to understand the coolant system a bit - particularly why tank rupture would pop a fault code indicating Vacuum Leak? where's the vacuum connected to this? Most of the coolant flow is pretty simple to grasp but I'm unable to find any information on the bleeder valve operation and the 2 hoses that come off of that - one is called Coolant Vent Line but again, I don't see any information on this. @Autobahnschreck or anyone who may know how this line works, to what it connects on the other end? And might this have any bearing on the Vacuum leak code? Or does the DME just state Vacuum leak by default when there's a loss of pressure in the coolant system in general? Thanks again and I'll follow-up once I've installed the new (used) Expansion Tank.
![](https://cimg7.ibsrv.net/gimg/rennlist.com-vbulletin/982x722/cooling_scheme_991_2c0015e9aad2a4a2684acceb712a8e96c8a91aa4.jpg)
Above see the cooling circuit of the 991.1 (Motor type MA1.0x ). The expansion tank (6) has two vent lines, for both the front radiators, the cabin heatexchanger and thetwo gearbox heat exchangers. If the comfort valve (5) is manually opened, it allows for venting residual air into the expansion tank.
There are 3 disc valves, controlling flow to the heat exchangers for cabin heat and for gear oil /clutch fluid. A fourth disc valves controls the "short circuit" of the cooling circuit from clyinder outlet to the thermostate. This valve allows for rapid switching to complete flow across the radiators, if required. All four valves are operated by vacuum. The respective vacuum lines are controlled by the infamous electromagnetic "change-over valves". The COV get their vacuum from the pump driven by the right exhaust cam shaft, as does the brake booster. Further ( up to 6) COVs are controlling flaps for air filter, intake manifold, and exhaust flaps.
What happens if there is a serious vacuum leak ?
a) if between pump and any COV: 1) the brake booster does not work 2) exhaust flaps remain open after starting the engine. Probably warning: reduced/missing braking support .
b) between any COV and its user: the respective user/ valve remains in its position, even if required to operate. Exhaust flaps remain open (you should hear it, if you try to quiet them).
When the motor/gear oil/ clutch oil warms up and requires action of the respective COV without appropriate response, the DME will through a yellow error messsage ( " ..fault in cooling system,..service required".
A joke shop technicians sometimes play on their customers is not re-connecting a vacuum line to the exhaust flap actors. This results in the above quoted message, but only after about 15 mins. of driving after taking over your car.
Finally, what does this mean if your expansion tank leaks and you get the message "vacuum leak" ? I do not see an immediate connection between both problems. Even if the leaking expansion tank leads to boiling at normal operation temperature and thus insufficient cooling of the gear-/ clutch oil, the error message would not refer to "vacuum leak", but "cooling system"
From MD's I learned, people may have fleas and lice at the same time, i.e. , there may be different root causes for even unlikely symptoms you (or your car) suffers from.
The following users liked this post:
dannyk304 (01-11-2024)
#17
Instructor
Thread Starter
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
![](https://cimg7.ibsrv.net/gimg/rennlist.com-vbulletin/982x722/cooling_scheme_991_2c0015e9aad2a4a2684acceb712a8e96c8a91aa4.jpg)
Above see the cooling circuit of the 991.1 (Motor type MA1.0x ). The expansion tank (6) has two vent lines, for both the front radiators, the cabin heatexchanger and thetwo gearbox heat exchangers. If the comfort valve (5) is manually opened, it allows for venting residual air into the expansion tank.
There are 3 disc valves, controlling flow to the heat exchangers for cabin heat and for gear oil /clutch fluid. A fourth disc valves controls the "short circuit" of the cooling circuit from clyinder outlet to the thermostate. This valve allows for rapid switching to complete flow across the radiators, if required. All four valves are operated by vacuum. The respective vacuum lines are controlled by the infamous electromagnetic "change-over valves". The COV get their vacuum from the pump driven by the right exhaust cam shaft, as does the brake booster. Further ( up to 6) COVs are controlling flaps for air filter, intake manifold, and exhaust flaps.
What happens if there is a serious vacuum leak ?
a) if between pump and any COV: 1) the brake booster does not work 2) exhaust flaps remain open after starting the engine. Probably warning: reduced/missing braking support .
b) between any COV and its user: the respective user/ valve remains in its position, even if required to operate. Exhaust flaps remain open (you should hear it, if you try to quiet them).
When the motor/gear oil/ clutch oil warms up and requires action of the respective COV without appropriate response, the DME will through a yellow error messsage ( " ..fault in cooling system,..service required".
A joke shop technicians sometimes play on their customers is not re-connecting a vacuum line to the exhaust flap actors. This results in the above quoted message, but only after about 15 mins. of driving after taking over your car.
Finally, what does this mean if your expansion tank leaks and you get the message "vacuum leak" ? I do not see an immediate connection between both problems. Even if the leaking expansion tank leads to boiling at normal operation temperature and thus insufficient cooling of the gear-/ clutch oil, the error message would not refer to "vacuum leak", but "cooling system"
From MD's I learned, people may have fleas and lice at the same time, i.e. , there may be different root causes for even unlikely symptoms you (or your car) suffers from.
The following users liked this post:
wkearney99 (01-11-2024)