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Re: If it is the bypass tube it usually..............

Thanks Guys,

Im losing about 8oz per tank of fuel so theres no highly obvious source of leak. Having replaced three head gaskets, hoses, crossover pipe, O rings,coolant pump and two expansion tanks in numerous visits to the dealer you'd I'd be expert in 745 coolant faults but there seems to be no end to it.

I was hoping for a miracle cure by adding a little radweld maybe to cure an inaccessible pipe fault. If it woudn't compromise the system it might buy a little quiet enjoyment of what is despite all its faults a magnificent car.

Regards

If it is the bypass tube it usually..............

..pisses a stream of coolant out of the front timing cover, there is a small hole in the timing cover where the coolant will come out of when the seal fails on the bypass tube. The engine WILL NOT hold coolant, you wouldn't even make into the dealer without losing almost all your coolant.
Where are they saying this tube is leaking?
It is inside the engine and cant be seen unless you disassemble the center section of the motor.

You really need to find the REAL location of the

leak before throwing more money at it. It sounds like they have not really found it. I would probably stay away from Stop Leak stuff.

Go to this thread and look up the link he gave

and see if this fits your problem. I have also posted this on the e65 board of bimm erb oard dot com where it is not censored.

Re: Coolant system repair products

I am having the same problem right now and my car is at the dealership as we speak. I had been getting a low coolant indicator light for the last two weeks but I knew I had a scheduled appoint coming up so I just topped off anti-freeze until inspection. Took the car in and they found that my cars auxilary water pump was not functioning they replace the auxilary water pump expansion tank and radiator cap. the next day when I start car I get low coolant indicator light and call service department they tell me to bring car back probably air in the system they would top off and make sure no big problem they kept car gave me loaner. this morning service representative calls me and tells me that my coolant bypass tube was bad and that it would cost approximately $5700 dollars to fix. I am in negotiatons with them because car did not have any problems just went in for normal service inspection now I am having problems with the same system that they worked on.......coincidence I don't think so

Coolant system repair products

My 02 745 is losing coolant (again). It needs a top-up about every 1000 miles. I've had several head gasket repairs and the crossover pipe done. Literally thousands spent out of warranty in addition to warranty works done. The car has 100k miles and is otherwise magnificent but Im reaching a point where Im considering adding a coolant system sealing product. Even after the last head gasket repair I was topping up monthly.

I often get a yellow engine light briefly on cold startup. I believe this is a little coolant boiling out of one of the cylinders. Usually clears within about 30 seconds.

I hear both positive and negative feedback on sealing products. Im worried about clogging up the heater matrix or the radiator itself. Ordinarily I'd just get the repair done but my experience so far is that repairing coolant problems is difficult, expensive and very unreliable.

Should I just keep topping up until it gets serious or would a chemical solution prevent things getting worse quickly?