I recently replaced the thermostat due to failure, now I seem to be loosing coolant but cannot find any external signs of leakage, neither can my mechanic.

I fill everything up (including expansion tank) but after a week (250 miles) the expansion tank is practically empty and the radiator is down a few inches.

Anyone know what the cause/cure is?

 

Thanks

It seems to me that the coolant may be getting boiled off somewhere. Perhaps either it's leaking somewhere onto something hot enough to boil it off, or it's getting into the combustion chamber.

 

Has the oil level risen? Does the oil look milky or muddy?

 

One way to pinpoint leaks is to park over a clean piece of cardboard.

I would think to make sure the whole system was filled with the full amount of coolant. Possible that there was a lot of air that wasn't "burped" when the coolant was added, leaving a misleading level of full coolant? After driving the air has been squeezed out?

 

Just a thought. I'm about to do the coolant swap here, soon, and the big issue that people tell me is the whole burpage thing.

Check the radiator on the front side near the right (driving direction) headlamp. There may be a vertical crack in the frontside of the housing.

Look close because sometimes it's not easy to see.

 

Urban.

If you are sure that you don't have any hoses that leak under pressure then you either have a intake manifold or headgasket leak.

My 86 is leaking from the turbo.Is this a possibility with you?If you have a Turbo,check where it meets up with the exh header of white residue.

I've re-looked at everything and there is no sign of external leak.

It can't be the turbo, cause I dont have one .

I checked the radiator for a hairline crack but didn't see any.

About the air trapped, it is a very small possibilty because I have added more coolant than the capacity of the system.

The oil level hasn't risen to my knowledge and the oil isnt muddy.

 

I'd now like to check the system under pressure. How is this done? What equipment do you need?

 

If there is still no leak under presssure, then it's an intake manifold leak or a headgasekt leak, is that for sure or is there another possibility?

Setright says it takes 600 miles to get all the air out of his soob.

 

I'd check the level, refill as necessary, maybe put the front up on ramps and run with heater on untill the fans come on. Let it cool, refill. Then watch it for a few weeks. If it doesn't change and there are no other symptoms, it may have just burped itself.

BUT, if you're sure you've put in more than system capacity, try comparing the appearance of the plugs to each other, an internal leak may alter their surface coatings from normal and you'know it's an internal HG leak.

 

very odd. good luck

I would back the hairline crack in the radiator end cap. These caps are made of plastic and is a usual cause of loss of water from the radiator.

When the radiator pressure rises the crack opens a very small amount to discharge water and when the pressure is relieved the crack closes. The closed crack is almost impossible to detect visaully. You can perhaps get an indication of the leak be observing if the bottom of the radiator is moist.

It can be tested by filling the radiator and then running the car to raise the pressure but you will need to look in the correct spot at the time it discharges because it will just squirt it out and the close the crack.

The best method is a pressure test

Regards

Peter