Pressure cap on expansion tank

[Mark 4.3]

Having a minor problem on cooling system of my 4.3BV Griff. It basically works well, running at 75-80 degrees on a run and up to the 88-92 range in traffic, with fans kicking in when they should. System has also been pressure tested, with apparently no problems. However it frequently pi**es out a small quantity of coolant onto my drive. I established that the coolant is coming out of the top of the expansion / swirl tank, via the pressure cap. At the point when this happens, the temp guage is only around 90deg, but I can hear that the coolant is 'excited' (if not on a full boil!). The system is not over-filled (tank about 2/3 full). Also I have to bleed the system very occasionally, so it seems there is some air ingress. Has anyone had similar experiences? Is it time for a new pressure cap, or something more serious? Or is it a case of "they all do that sir"? Thanks for any comments....

[neilmac]

My 500 chucks a bit of coolant out after parking it up for the night, can't find a leak and I think I have cured it by making sure the Blue cap is done up really tight. I think I remember the previous owner saying something along the same lines come to think of it.

I expect a new cap is probably the answer.

[HomerJ]

For what it's worth my S2 (not the same I know but....)used to p out the contents of the exp tank from fairly early on, esp after parking if it was a bit warm. If I didn't refill it, it didn't do it, and no other water loss, checked regularly via the swirl tank. So I gave up worrying about it. No further problems in at least another 5 years of ownership.

Ditto the new cap suggestion though. Changed an old one which looked fine (re above) for one with a rubber seal, and cleaned up the surface to meake a good seal (to swirl tank). Ran a notch lower on the temp guage after that.

Suspect there's more threads on this elsewhere - more technical too!

Good luck.

[Patrick L]

I get my 500 serviced by David Batty, a specialist in Surrey, who has advised me on this specific point. Only fill 1/2 way max. It has worked for me.

[Mark 4.3]

Thanks for the advice guys... think I'll get a new cap and stop topping it up so much!

[simpo one]

I know the 500 is different from a 4.x in having a sepearate expansion tank but my experiences are thus: 4.0: level in swirlpot 1" below bottom of side tube - no problems at all. 500: level halfway up expansion bottle - piddles a little coolant onto garage floor. It doesn't come from the cap, in fact I've never found where it comes from. But once the level is a little below halfway, it's happy. Bizarre!

[bogbeast]

neilmac said: My 500 chucks a bit of coolant out after parking it up for the night, can't find a leak and I think I have cured it by making sure the Blue cap is done up really tight. I think I remember the previous owner saying something along the same lines come to think of it.

Ditto mine. I noticed water marks appearing around the cap, a good tighten and its fine now. I have also added water wetter and fitted a lower temp otter switch (from Leven) and this has really evened out the temp (no more spiking to 100c) and I rarley have to top up now..