Expansion tank question

[TimShoubridge]

As some of you know, I've fitted the Mercedes expansion tank setup to my car along with a 16" electric fan. All seemed to work ok until the Brands Hatch meeting. Whilst we were sitting outside the gate waiting to get in my gauge went up to a needles width from the red, however, the fan cut in and kept it stable. This is the only time it's done this and it behaved well on the run there and the journey home.

The other odd thing is that the water level in the expansion tank rises about 1in or more from cold to hot. There is no pressure release, the hoses are the correct type and are all fitted well (no leaks) but it is clear that the whole system is under pressure, maybe more than I'd like.Once all cools down the level returns to normal.

Now I know the "Stag paranoia" is with us all but this jst seems odd. I can understand the temp rise but am stumped by the apparant pressure issue.

I haven't fitted my electric pump yet but this makes me think it will be a good idea.

Any ideas?

[sjm]

imported post

TimShoubridge wrote:

As some of you know, I've fitted the Mercedes expansion tank setup to my car along with a 16" electric fan. All seemed to work ok until the Brands Hatch meeting. Whilst we were sitting outside the gate waiting to get in my gauge went up to a needles width from the red, however, the fan cut in and kept it stable. This is the only time it's done this and it behaved well on the run there and the journey home.

The other odd thing is that the water level in the expansion tank rises about 1in or more from cold to hot. There is no pressure release, the hoses are the correct type and are all fitted well (no leaks) but it is clear that the whole system is under pressure, maybe more than I'd like.Once all cools down the level returns to normal.

Now I know the "Stag paranoia" is with us all but this jst seems odd. I can understand the temp rise but am stumped by the apparant pressure issue.

I haven't fitted my electric pump yet but this makes me think it will be a good idea.

Any ideas?

Hi Tim,

Sorely this is the idea expansion, water level rises when hot and under pressure then returns back to the level you have set up in your tank when cold.

I have the standard set up but I did notice when I returned from Brands that my expansion bottle was slightly higher than normal , but I did give it some on the M25 until I hit traffic at the A3 junction.

But all back to norm the next day Stag paranoiayou worry to much and this will spoil your driving pleasure with the Green Hornet.

Regards

Steve

[stagstr]

imported post

TimShoubridge wrote:

There is no pressure release

Hi Tim,

Do you mean there is no pressure release facility or that the pressure did not rise above the 20lb release level, therefore there was no release of water?

If it's the latter, then all should be OK. Have you removed the viscous fan? If so, then under idle there will be no air cooling whatsoever and the water temp will continue to rise until the electric fan cuts in to provide a cooling draught. So, how far the needle goes over to the red, is determined by where you have the fan cut-in set.

However, if you have a viscous fan as well as the electric one, then you need to investigate if it is working.

I think Boyles Law applies here (school 'O' level Physics and all that) I think this means that PV/T is a constant. So if the temperature rises (T) then either or both the pressure (P) and the volume (V) will. Hence the rise in water level when hot, returning to normal when cool.

Can you let us knowwhy you think there is apressure problem?

cheers

Ray

[TimShoubridge]

imported post

OK....Paranoia it is then.

There is a release system and it did not cut in, so no issue there. The water level does go back as I said so again, no issue.

Viscous fan in place and spins correctly when tested.

Electric fan now set at lower temp so should cut in earlier.

Just need to sort the gearbox fluid leak onto the exhaust system now.

[Arbman Al]

imported post

TimShoubridge wrote:

OK....Paranoia it is then.

There is a release system and it did not cut in, so no issue there. The water level does go back as I said so again, no issue.

Viscous fan in place and spins correctly when tested.

Electric fan now set at lower temp so should cut in earlier.

Just need to sort the gearbox fluid leak onto the exhaust system now.

Hi Tim,

No joy in finding out where the fluid is coming from then?

Al.

[TimShoubridge]

imported post

arbman101 wrote:

Hi Tim,

No joy in finding out where the fluid is coming from then?

Al.

Al,

No joy in finding where from.......plenty of evidence of where it's going to.

May be time for a recon BW35. Can't afford the ZF conversion.

[Arbman Al]

imported post

TimShoubridge wrote:

arbman101 wrote:

Hi Tim,

No joy in finding out where the fluid is coming from then?

Al.

Al,

No joy in finding where from.......plenty of evidence of where it's going to.

May be time for a recon BW35. Can't afford the ZF conversion.

I have got a BW35 sitting in my garage...

it was the original box for my Stag before being converted to a mod.

[Guest]

imported post

TimShoubridge wrote:

Just need to sort the gearbox fluid leak onto the exhaust system now.

Aw don't fix it ! love the smell, ignore the smoke. Martin.