Coolant Loss

[MarkTwo]

Hi, I am looking for some advice on coolant loss. The engine does not overheat, has Kenlowe fans and engine oil cooler with original Mk 2 overflow bottle. Several times now having driven 20 - 50 miles, there has been no issue, no coolant loss, but I park the car and several hours later there is a small coolant loss under the car, which looks as if it is coming from the drain tube of the overflow bottle.

On running the engine up to temperature stationary or even when I get back after a drive, there is no leakage I can see. I have also tried opening the heater and topping up the coolant system via the top left radiatior plug. It does gradually reduce in level, ending up in the overflow bottle from what I can see.

I guess this could be a head gasket problem, but no water in the oil and no real problem yet, apart from having to top up again. Any checks recommended?

Thanks, Mark

[martin]

Hi Mark, it is possible that you're over filling the expansion bottle and it's finding it's natural level, this can vary from car to car, but often winds up at about a third of the bottle. Never fill it past half way, it'll just chuck it out. Another possibility, is a leak past the brass neck on the bottle. Martin.

[jleyton]

Are you sure your expansion bottle isn't overfilled ? It should only be about half full when cold.

Cheers

Julian

Oops - too slow

[MarkTwo]

Hi Julian and Martin,
I had it higher than half when I first refilled it and thought it needed more room for expansion when hot, but now it is less than half and it has still dumped some coolant, albeit a small amount this time. I feel I am fast getting the Stag paranoia!! Only aftter 3 weeks as well.
Mark

[jleyton]

Ok, so try it next time with just a third full and see how it goes.

From what you've said so far, it doesn't sound like head gasket to me so put that paranoia to one side for now

Cheers

Julian

[ampotter]

Hi Mark

How old is the pressure cap on the expansion bottle? If this has a weak spring or the rubber seal has deteriated, it will allow coolant to escape. The cap should be rated at 20lbs.

Andrew

[Stevekid1]

Hi Mark, I had similar problems with mine early on, bottle used to fill up and i would end up syphoning coolant out of the bottle and putting it back via the rad filler. Go for no more than one third full in the bottle. Top the radiator up via the neck filler. Sqeeze the top hose so that the water is at the top of the filler neck and add coolant as you gradually release the hose. This I find avoids the air lock. Finally, change the expansion bottle cap as Andrew suggests for a new one of the correct pressure and with any luck the problem will be solved. I only ever fill the system via the radiator cap not the bottle but since I changed the cap on the bottle I rarely have to top up. Previous to that it was every time i used the car.

Steve

[silverfox]

Hi Mark, I had a similar problem and eventually found the coolant was leaking between the metal ring at the neck of the bottle and the plastic bottle neck. I just put some araldite all round the neck where the metal ring fixes and it cured the problem, Terry

[StagnJag]

Probably worth checking for leaks arounf hte neck of the bottle and the cap. Take the bottle off, complete with the pipe, empty it and try and rig up some way of pressurising it using a tyre foot pump with a gauge or something like that. Dunk the bottle under water and look for bubbles. (It won't take much to reach 20psi so go easy.

Rgds

Dave

[MarkTwo]

Thanks for all the advice. The radiator cap was bought new 2 years ago and the prior owner only did about 500 miles in those 2 years. It looks new still. It is still leaking coolant over night, despite the bottle being only 1/3rd full. I have it booked in a local garage that works on a number of Stags. They are going to pressurise the system and check for leaks. So we will see if they find the problem. Otherise I will take the bottle off and pressure just that.

Regards, Mark