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Hello David
I have had coolant leaks with the B280F, and they can be a bit of a bear to track down. You've received some good advice to date, but some of it does not apply to your car.
Fundamental checks:
1) oil dipstick-- does the oil look normal on the stick? It should be somewhere between honey and black like ink, but definitely not like a chocolate milkshake. If there is milkshake oil, you are leaking your coolant into your oil.
2) Transmission fluid at the dipstick-- does it look clear and pink? If it looks like strawberry milkshake, your transmission fluid is being contaminated by coolant.
3) Exhaust pipe-- when the car is warmed up from driving for a while, is there any white smoke at the tailpipe? Particularly if it smells a little sweet, then you have coolant being burned by your engine (leaking into the combustion chamber). Another useful thing to do is remove one spark plug at a time and look for one that looks perfectly clean compared to the other-- this would suggest a head gasket leak.
4) Coolant recovery tank (where you put the coolant in)-- is this part full of oily scum? That would indicate an oil leak into the coolant.
If not, then you most likely have an external leak. Look in the valley between the banks of cylinders-- is there coolant (green) or a white crust in there? Carefully inspect all the hoses, the heater control valve, the base of the coolant recovery tank, the radiator tanks and hose inlets and outlets. Look at the water pump (behind the fan on the motor), particularly at the back where the gasket is. There are coolant bypass hoses that go into each head-- the gaskets leak where the steel hose bosses attach to the aluminum heads (dissimilar metal problem resulting in corrosion). There are to hoses exiting the back of the water pump, one big fat one and a smaller one. Check those carefully. Sometimes getting the car warm and then looking immediately after shutdown is the best way to find leaks-- the system is still pressurized to some degree but nothing is moving anymore.
Definitely shampoo the motor-- get some engine shampoo spray and take it to a pressure washer-- don't blast electrical components-- otherwise it is pretty safe.
Leave cardboard under the engine compartment after you shut it off and check an hour later for stains.
Practical concerns-- watch your coolant level very carefully-- keep it topped up. Watch your temperature gauge-- if is getting hot, stop driving it! You need to find a mechanic who is willing to work on this car and who has the know-how and access to special tools. Taking a head off of one of these cars is not trivial-- there are steel cylinder liners inside the aluminum bores-- if the head is removed incorrectly, the liners will move and you will have coolant leaks at the base of the cylinders and you will have a whopping repair bill. Any shop should be able to pressure test the system to locate the leak if you can't find it yourself-- you may get lucky and just need hoses or a radiator.
Good luck-- those 760GLEs are nice cars-- they tend to be bargains because of the undeserved bad reputation of the B280F, which is actually quite a robust motor.
--
Herb Goltz, London, Ontario, Canada '92 245 w/109K mi
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