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[YZ250]

I need to do a sniff test, just to be sure,..I'm puzzled with this one

If you’re losing coolant now you could try a pressure test, with a schrader valve in the coolant tank cap. There may be a guide on here somewhere. I’m wondering if the HBV could be failing.    You have low/no cabin heat and engine coolant temp apparently affected by vacuum (revving). 

[danzigfan]

To many things...will check for oil in coolant tomorrow and start from there. Oil could block heater matrix too

[TheBoy]

OK, as its rust and not oil, oil cooler is fine.

The bottles sometimes develop hairline cracks around the base of the neck where the cap screws on.  The other common place for weeps in is the plastics one the end os the rad.  Both these are hard to find as they only happen when pressured.

If you still have you old cap, modify it to remove pressure valve, and put in a Schrader valve.  Put it on, and pressure the cooling system to 8PSI (no more!).  Then visually inspect for leaks.  If the pressure drops over time, it's leaking somewhere.


The fact that the water is rusty does show the coolant has lost its anticorrosion properties, and will need flushing through ASAP - not the easiest on Omega V6 due to no block drain.  You may simply want to replace the coolant 2 or 3 times in quick succession to get the rusty stuff out, and get the mix up to strength.

[TheBoy]

Like this (sorry it's photo bucket, not got a local copy of the pic)

[danzigfan]

Yes, I will do that and pressure test it, thanks. I'll upload pic of the result of 90 minutes motorway drive from yesterday...It seems like coolant bottle "puked" all over air filter housing. Some thoughts please

[danzigfan]

[TheBoy]

Can you tell if it over pressurising?

If it's not, it's either the cap or the bottle looking at that.  Again, using a modified cap allows you to pressure test it all up to safe values (not sure what the release pressure is on the cap, not got one to check - it will be written on it.  Defo keep it well below that figure.

If no leakage when testing, it must be overpresurising, and the cap doing its job and spewing it out.

[danzigfan]

I think it's overpressurising. See, with old cap, the hoses were really hard and small leak appeared on the weakest point of the system - in my case on the top of radiator where fan switch lives.
With new cap, it seems that pressure releases trough the cap and hoses stay always soft. I'm really afraid of head gasket again, although it was fine for over a year after heads were off.

[TheBoy]

Which engine is it, and what year is it?

As a rule, V6 HG are rock solid, and almost unheard of for the firings to fail.  97.5 model 3.0l engines (so the very first of the 98MY cars) occasionally allow coolant out to the outside of the engine via the HG, at the back of cylinder 6

[danzigfan]

I'm waiting for a sniff test to arrive, if it'll show there's no exhaust gasses in system I m going to build pressure test cap and replace thermostat and flush entire system with some washer tablets at least three times and than replace with new coolant.

[TheBoy]

It's worth making the test cap anyway, if you have an old broken cap.  A valve can be got from any tyre place.  Bodge it in and seal the valve to the cap.  Keep it in the shed until you get an coolant leak, and it's ready to test

[danzigfan]

It's 2000 model 3.0. Gasket was leaking inside the system around two years ago but it was also visibly rusted trough at the back oc cylinder 6, so yes it was classic fail

[TheBoy]

It's 2000 model 3.0. Gasket was leaking inside the system around two years ago but it was also visibly rusted trough at the back oc cylinder 6, so yes it was classic fail

Unusual on a late 3.0l, assuming it's the original engine.

Rusted through does sound like you have a recurring issue with coolant strength - you should be using a coolant with corrosion inhibitors, and changing at the required interval (2 or 5 years maximum, depending on type used).

[YZ250]

……..
Again, using a modified cap allows you to pressure test it all up to safe values (not sure what the release pressure is on the cap, not got one to check - it will be written on it.  Defo keep it well below that figure.
……..

The caps are rated at 1.4 bar, but as said, no need to go anywhere near that figure.

[danzigfan]

Just did a sniff test...blue liquid turned green and lot ob bubbling inside liquid....Head gasket failed again only two years after both were done...I'm at a mental crossroad now...