The V8 Owners Forum -

After a recent possible overheat (hose blew off, warning light came on and I pulled over) my car is using coolant. 20 miles drops the level of the tank about a inch.

I have a kit car with a Rover 3.9l V8. I bought the short block off a guy from eBay as a 'new' reconditioned block that V8 developments had pressure checked, a balanced crank, new shells, rebored with new pocketed pistons. Supposedly it had top hat liners in as well but they didn't look like top hats to me. (knowing nothing about engines at the time I took his word) I have no paper evidence this was all done but the block certainly looked new, the pistons were pocketed and the bores newly honed with zero evidence of wear. And the crank had evidence of balancing. The cooling system has a radiator from a TX1 black cab with a non-pressure relief cap on. The header tank is a VW globe type.

There is no evidence of pressure in the system. The pipes are still easily squeezable when warm. 30 minutes after the engine has stopped you can open the header tank with a gentle hiss of air. No sign of oil in the water or water in the oil. When cold starting there is not very much smoke from the exhaust, if I blip the throttle a normal amount of smoke comes from the exhausts.

The car heats up as normal and drives as normal. When sitting in traffic the fan kicks in pretty swiftly but the temp gauge drops when the fan kicks in.

I can't find any leaks anywhere, I did 35 miles last night and put about half a litre of water in afterwards. Got a torch out a searched for leaks but I can't find any.

The only evidence I have to where the water is going is on first filing the water system up and rebleeding, the system chucked water out past the seals of the rad cap. I assumed I had overfilled the system and the pressure found the weakest point (why the pressure relief on the header tank didn't go first I don't know), or I hadn't screwed it down correctly.

I am struggling to believe the water is leaking and I am not finding a leak. This points to a blown head gasket (tin) or a dreaded dropped liner. But I have no evidence of either.

Any thoughts?

when you remove the cap when the car is stone cold - does any air/pressure escape?

if so, hg or block is likely cause i'm afraid.

Eliot wrote:when you remove the cap when the car is stone cold - does any air/pressure escape?

if so, hg or block is likely cause i'm afraid.

No, no pressure in the system after a few hours

It's very much easier to check for leaks etc using a pressure kit so you can pressurize the system with the engine stopped. You might then hear a leak the engine noise would cover. Other trick is to add a UV dye and check in the dark with a UV light. A tiny leak can evaporate and leave no trace. The dye shows where it is.

If it tests ok cold, heat up the engine and repeat.

Best to make absolutely sure it isn't something simple before thinking liner etc problems.

Ok
You have no idea if the system has filly burped all air or not
You also have an idea you are losing coolant
So
Drive the car, let the coolant overflow and then find its own level and once cooled mark header tank with level

Then do not add coolant

Take for another drive and then allow to cool
Has coolant level changed or not? If not that is the level at which your system will run at
If yes then either it has burped more air, it has, had a hot spot which caused steam and blown out some coolant, it has a leak somewhere, like past water pump seal, hose etc. Or lastly there may be a problem with the engine

That is the order I would imagine it would work out.

If you still consider it is the last option take out your spark plugs
If you are leaking into a computation chamber one or more plugs will be steam cleaned

Ian