My Cooling system - Still not right - what now?

[SD1too]

I have just started my KV6 from cold and remembered to remove the expansion tank cap to see what was happening with the small bore hose at the neck. My engine is not suffering from the symptoms described by Ps3000 and heli flyer.

There was a steady stream of coolant being returned to the expansion tank by the small bore hose with no air bubbles whatsoever.

So it seems that it's back to the drawing board with this particular theory:

Originally Posted by T-Cut

There isn't a flow through the small bore pipe pipe under normal running conditions. The bore is too small and it's clearly not designed for that purpose.

I hope that this is reassuring to those with problems.

Simon

[heli flyer]

Hi Simon,
Funnily enough, I have just done the same check as you and I have a steady stream of coolant too. Seems I have got rid of, maybe, some residual air since being sorted. I wonder how Ps3000 is getting on. At the moment, I have cleared the plenum drain and now on to sort the airbag light (again!)

[Ps3000]

Well, I've been using the car for a few days since I bypassed the oil cooler and it's been behaving reasonably well.

Upon start from cold, I also now get the steady stream of water from the little pipe back int the tank.

Today I didn't use the car at all - last trip was at about 8pm last night, so at lunchtime I removed the coolant cap.

There is still a huge pressure difference - I honestly can't tell if it's pressure release or vacuum.

I am still losing water somewhere. I estimate I needed about 100-200 ml to get back to max. I am not unduly worried or unhappy at present - I am going to run it like this until something breaks or it cures itself. I have a full spare engine in the garage and I'm saving up for an engine crane

I am not going to do the blowby/leakdown test for now - if I have a cracked liner or HGF, they will fail "properly" eventually and there's a heck of a lot of work to get to a point where I could turn the engine over by hand to TDC on each of six cylinders to do the test as well as having to make up the tester.

Thanks everyone for your input. I promise to come back with a further update when I have more news. I also promise that the car won't be abandoned or scrapped if/when it lunches it's engine.

[T-Cut]

Originally Posted by Ps3000

Upon start from cold, I also now get the steady stream of water from the little pipe back into the tank.

It's a meaningless 'test' and tells you nothing. It will stop when the pressure cap is in place. It's primarily to allow air out of the head when refilling/bleeding., which is done with the cap off. There's a natural flow as the head contents expand and also because it's being pumped. The cap blocks it off.

- - - at lunchtime I removed the coolant cap.
There is still a huge pressure difference - I honestly can't tell if it's pressure release or vacuum.

It's pressure for sure. Any possible vacuum is relieved by a hair spring valve hidden in the cap housing. It relieves at miniscule vacuum. A significant hiss when opening the completely cold system is due to exhaust gas. I believe your diagnosis above is correct. Thanks for the update.

TC