Mystery disappearing coolant

[Rob B]

Hi Guys,

Wonder if anyone can shed any light on my mystery coolant leak - if indeed thats what it is.....

The problem only seems to have developed since i moved it up to Manchester, no hint of it when it was down at my mum and dads in Gloucestershire (maybe it doesnt like the weather!). Shortly after bringing the car home i noticed that it had lost some engine coolant, radiator level was well down and the overflow bottle was empty. Checked all the usual points where they leak, everything seemed dry, no sign of any fluid on the driveway. So i topped it up thinking that perhaps the car had just cleared an air lock and the level had dropped. Car drove fine, temp gauge never went higher than half, no signs of overheating so i just put it down to "one of those things".

A week later, checked the levels and same again, coolant level had dropped but no visible signs of a leak. After much head scratching i noticed a tiny dribble of water coming out of the radiator cap, running my finger round the cap revealed it to be quite wet. Took the cap off and when i looked at it the seal was completely knackered. Problem solved i thought, evidently as the engine was pressurising the system it was forcing water out through the worn seal and the coolant was then evaporating on the hot engine, hence why i couldnt see any leak.

Ordered a new cap from Rimmers, topped up the system again and the car has been fine for the last week. Until today........... really thought thats what it was but this morning when i checked the engine the coolant had dropped again and once again the overflow bottle was empty. Now the stupid thing is i havent driven the car for the last 3 days and it hasnt rained, so if it is a leak i would expected to have seen signs on the drive but its bone dry. It cant have blown it out of a weak point whilst going along cos as i say the car hasnt moved for 3 days and the level was fine when i parked it up. All the hoses feel dry, its dry round the radiator cap and along the bottom of the rad, water pump feels dry, interior of the car is dry so its not leaking back into the cab anywhere........... frankly im at a loss.

After speaking to my dad, our thoughts are that it could be a massive airlock in the rad, meaning its not actually as full as i think it is. The rad has been repaired before and non too well by the looks of it.

Any suggestions/advice gratefully received, is it worth just changing the rad to rule it out?

Cheers

[Alec]

Hello Rob,

I've never experienced an air lock in a radiator and think it would be unlikely in a car that runs at normal temperature which indicates the core is pretty clear internally.

A pressure test would be one way to check or even after a good run so it is as hot as possible. One weak point, I don't think you mentioned, is the steel tube that runs behind the manifolds. They do corrode and you could have a pin hole developed which would be obvious under pressure, although you may need to crawl underneath to see it?

[Jonathan Lewis]

Rob,

I have had a 2000 radiator airlock, but once only, and which resulted in the engine running obviously hot - cured by jacking-up the front of the car, supporting it on stands and running the engine with the radiator cap off until all the air/steam had been expelled, refilling with new coolant at the same time.

I suppose that it is possible that you might have had an airlock in the heater which gave a false high level when last you refilled, but which has now purged itself out, hence the unexplained drop in level.

If coolant is actually escaping under pressure, I'd expect to see stains adjacent to the point of leakage. As you say, after a good run, there's usually enough heat in the engine compartment to flash off any water, but the tell-tale blue-grey marks usually remain...

One thought - does the car still have the drain taps on the radiator bottom tank or engine block? If so, are those leaking at all?

Regards,

[CAR]

Rob, when I bought the estate it was loosing coolant with no apparent sign.
One day whilst doing something else I noticed a drip under the car.
The engine had been off for 5mins or so and was leaking from a very small 'vent' hole at the back(underneath) of the water pump. Didn't show itself until the car had been stopped for a bit though!
New water pump cured it, but there were no other signs, overheating etc.

Cheers Colin.

[Rob B]

Rob, when I bought the estate it was loosing coolant with no apparent sign.
One day whilst doing something else I noticed a drip under the car.
The engine had been off for 5mins or so and was leaking from a very small 'vent' hole at the back(underneath) of the water pump. Didn't show itself until the car had been stopped for a bit though!
New water pump cured it, but there were no other signs, overheating etc.

Cheers Colin.

Thanks Colin. Im really glad you have said that because this is now finally starting to make sense. When i collected the car from my parents my dad and i ran it down to the local garage for some fuel. When i pulled up at the pump we noticed quite a sizeable puddle forming under the car. When we lifted the bonnet it seemed water was leaking from the water pump itself.

We limped the car home (less than a mile) popped the bonnet again - no sign of a leak. We ran it for ages and checked all over for a leak but found nothingand the level hadnt dropped noticeably. In the end we put it down to the fact that Dad had accidentally soaked the engine with the hose when he did the anti-freeze earlier that day and that it was jsut a puddle of water that had lingered somewhere.

Of course ive subsequently discovered that the radiator cap was leaking, so that explains some of it but now, hearing your experience im thinking the water pump is at fault too. Or maybe even just a knackered seal around the pump? Happily i have a good spare pump that i took off the scrap car so thats my next job.

Cheers!

[TedTaylor]

Rob

I strongly recommend that you invest in a new pump unless you know that the pump you plan to use has done minimal mileage and has not been standing for very long on the engine. You don't know whether the pump is at or near the end of its working life and precisely how good the bearings and seal are. You could end up with you going to the hassle of fitting the pump and having to redo again within a few thousand miles.

I will quite happily recycle most bits off scrapped cars if they appear in good condition ......... but the water pump is one that I would not re-use unless of known low milage or attached to an engine that I was swapping and engine had been run and pump ok (but even then I would consider changing).

Simplest check for your old pump is to remove the drive belt, grab the pulley, and check for sideways movement. If there is any then pump IS useless, but even without the play the seal could still be on its way out.

Ted

[Alec]

Hello Rob,

it is possible for a small bit of debris to unseat the seal and cause it to leak and then reseal, (the tell tale drain hole being designed so that a passing seal has a chance of being noticed and diverts water from entering the bearing.)

However, water from there is never a good sign so keep a close eye on it.

Alec

[Rob B]

Rob

I strongly recommend that you invest in a new pump unless you know that the pump you plan to use has done minimal mileage and has not been standing for very long on the engine. You don't know whether the pump is at or near the end of its working life and precisely how good the bearings and seal are. You could end up with you going to the hassle of fitting the pump and having to redo again within a few thousand miles.

I will quite happily recycle most bits off scrapped cars if they appear in good condition ......... but the water pump is one that I would not re-use unless of known low milage or attached to an engine that I was swapping and engine had been run and pump ok (but even then I would consider changing).

Simplest check for your old pump is to remove the drive belt, grab the pulley, and check for sideways movement. If there is any then pump IS useless, but even without the play the seal could still be on its way out.

Ted

Good advice thanks, given that new ones arent that dear i shall invest.

[Rob B]

Hello Rob,

it is possible for a small bit of debris to unseat the seal and cause it to leak and then reseal, (the tell tale drain hole being designed so that a passing seal has a chance of being noticed and diverts water from entering the bearing.)

However, water from there is never a good sign so keep a close eye on it.

Alec

You saying it could be symptom of something else?

Im not overly worried as the car pulls like a train with no sign of overheating. Were it not for the overflow bottle empyting all the time i would never know anything was wrong.

[Rob B]

Gotta hope for a break in the weather to try and do it now as i dont have a garage big enough to work in and im a little concerned that i might not be able to get it back together again in a single weekend if i encounter problems and i cant really afford for the car to be off the road