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[Fresno Bob]

Hi guys,

My 1999 2.0 16v is using considerable amounts of coolant, but I cant find an obvious leak anywhere.

All I can see is a slight (and I mean slight) weaping around the top joint of the expansion tank (just below where the cap screws on)

I have run the car up today from cold, drove it around the block but no evidence of a leak to account for the amount I am loosing. I have monitored this weeping and if I wipe it away, it takes a good 5 mins to build up again. I know I will have to replace the tank, but it does not seem that htis is the main issue, more a red herring?

As an example, topped the water up to the cold line at work, drove home (18mile journey) aprox 12 miles into journey, indicator panel in car is telling me low coolant level.

When I let it cool down, sure as eggs is eggs it is well below the cold line?

Many Thanks

Lee

[Brikhead]

As long as there are no signs of water and oil mixing, and no excessive white smoke from the exhaust, then you must have a leak.
You mention the expansion tank, sometimes these start to crack around the top half and allow loss of pressure and coolant vapour, It would be a good idea to get a replacement...

[Fresno Bob]

There is no visible leak, I have white smoke upon start up, but appears to clear when warm.

I have my replacement tank ready to fit this afternoon when engine has cooled down.

Just seems a lot of water to loose to what is a pin hole at the top of my expansion tank?

[Entwood]

If the header tank cap has failed, the seal is poor, or you have small cracks around the threads  .. the same thing happens in all cases ... the system will not pressurise.

If the system is unpressurised the boiling point of the water is lower. As the engine runs at just below boiling point (97°C) it is very close to boiling , its almost like "simmering" a pan on a cooker. So evaporation will take place at a high rate. This can lead to an apparent drop of level very quickly.

Make sure the system is SEALED .. as it was designed to be .. the few PSI pressure raises the boiling point to around 105°C and prevents evaporation.

HTH

[Fresno Bob]

Replaced expansion tank, no leaks etc from there.

Car is still loosing water, no obvious leaks / puddles, oil looks ok, no gunk on oil cap.

I am fresh out of ideas :-/

[ScaniaV8]

Pressure test the system, the only real way to see where leak is coming from in the system. There is a guide on how to do this check.

Also, have you definitely concluded it's not the obvious candidate....the HBV. Depending on heater settings you can lose alot of ccolant very quickly if it is faulty. They are a regular culprit...and only fit a genuine VX replacement. 

[Abiton]

To reassure yourself about the head gasket, try the following.
With cold engine, remove sparkplugs, ensuring that any fluid around them is mopped out before you unscrew them.

Shine a small bright torch down each hole in turn, looking at the top surface of the piston.  If there is fluid on any of them, sample it with a bit of kitchen roll taped to a stick.  If it looks/smells/tastes like coolant, that would be bad.

If they are all dry, that would be good.