Strange coolant loss

[klaus]

Hello,

I have a strange problem on my 1974 P6 3500:
Everytime I take my P6 out for a ride, put it back in the garage and have a look the next day there's a little puddle below the LH side of the engine bay, I suspect where the heater hoses meet the heater matrix. Also, the small raked bulkhead panel below the bottom heater hose mount is a little wet. So far, so obvious.

Now to the puzzling part:
When at operating temperature and pressure, the system is perfectly watertight. You would expect that under pressure water seeps out somewhere, but it never does.

It seems to me that a gap widens when the system cools down and still is under pressure, releasing up to a halfpint of coolant every time. I had this checked by a very competent mechanic already, but he had no clue what could be wrong here.

I am a little worried as next week I am going to take my P6 from Zurich to Salzburg to the International Rover Meeting. Can someone give me advice on whether this is a severe problem and what I could do about it?

Many thanks,
Klaus (Zurich, Switzerland, P6ROC-Member 1490)

 

[BBLongman]

Could it be the matrix itself is leaking and the water is running out of the heater box onto the bulkhead.

You could maybe test for a leak in this area by temporarliy connecting the two heater hoses together and taking the matrix out of circuit. Since it's the summer you could always make your journey like this if it solves the problem.

(I use 15mm domestic copper for these connections if you solder half a solder ring straight coupling on the end it gives a ridge to stop the hose slipping off under pressure)

Bennet

 

[DaveHerns]

Maybe it leaks when hot and only trickles out later because of the angle it's parked at ????? Have the system pressure tested - it won't cost much and will show up any leak

I suppose you haven't got Air Con ? you always get a little puddle when parked as ice melts off some part or another
Dave

 

[02GF74]

bear in mind the thermostat openms when the water is hot thus the water flows in different part of the system.

Does this happen when you are running the engine from cold and idling until it reaches tmepearture? when doing this, are you able to crawl about to look for leaks?

You need to pin point the place that is leaking from. Try dusting varous bits and pieces with chalk dust or talc; it will be washed off by the water.

 

[klaus]

Hello

Thanks for all the info and advice. I think I'll do the following:
- I will try to fasten the heater matrix hose clip screws more strongly
- If no success I'll try the dusting method
- Lastly I'll have the system pressure-tested

I'll keep you informed on the results.

Greetings from Zurich,
Klaus

 

[klaus]

Hi all,

just found that rather old msg of mine about coolant loss. I thought I might let you know how this problem was solved:

I went to a Viennese (I now live there) mechanic & P6 nut who uses his 3500S almost every day. He suggested a faulty head gasket, which allowed to push the exhaust fumes into the coolant circuit, thereby increasing system pressure up to a point where some water blows down the overflow pipe to return to operating pressure (15 psi, that seems to be). So I had both head gaskets replaced and the problem was indeed solved. Now holds coolant level like a car with header tank, I'm very pleased. Somehow the guy even managed to bing down fuel consumption from almost 15 ltrs/100km to around 12-13 (no idea what mpg figures these might be). By looking at the old gaskets it was even possible to identify the spots where the pressurised exhaust gases made their way into the water jacket.

The tiny puddles under the heater matrix seem to have been completely unrelated, being drips of brake fluid. As my 3500 is a Swiss model, it has a dual circuit system with one of the two fluid reservoirs near the LS of the heater matrix. The problem was fixed (so I guess) by properly screwing on the reservoir's lid.

Hope this is of help to anybody.
Cheers, Klaus