Dreaded over heating

[Gilespfr]

Hi folks
I haven't been on the forum much recently (three kids, own business, recession!). There's loads of good stuff about over heating. My Stag has run beautiful since I've owned it from last June. But over the weekend (OK it was 30 degrees), it went into the red on the temp. gauge for the first time ever. On firing it up yesterday, it did the same. I have recently topped up the coolant for the first time. So am assuming that the thermostat has gone, is that the most likely thing? The first time it happened on Saturday the coolant had clearly boiled over and we had a good 'smoke screen' of coolant steam. Luckily it happened locally to where I live.

Thanks for your help.

Giles

[V Mad]

You may have run low on coolant without realising.

[MarkTwo]

Giles , Did you fill up at the overflow bottle or via the brass plug on top of the radiator? Presuming a Mk2 stag.

Mark

[Gilespfr]

Mark, Chris
Thanks for your help. I've read a few people have taken their thermostat completely out, are there downsides to this approach for Mk2 if this is the prob for oveaheting?

Cheers
Giles

[GDPR]

Definitely not recommended for a mk2 - it needs the bypass foot to close off to get the flow right, and a good thermostat will not impede flow. Usually to get to the red quickly, there will be no coolant, a stuckclosed stat, water pump failure with either the drive gear failed or the impeller adrift from the shaft so no circulation - or the dreaded HGF.

Top.the coolant up correctly, then run it up trying the hoses for temperature, going hard through pressure and cold spots in the rad. When you have more info, get back to us for further clues....

[Gilespfr]

That's a great help thanks, why did they change the theromstat form Mk1 to Mk2?

Cheers

Giles

[GDPR]

If I remember correctly, they changed the waterways in the inlet manifold so that a greater proportion of the cylinder head coolant could be bypassed back to the water pump when the thermostat was closed to give a faster warm up. To restore the coolant flow to normal, the thermostat had a sprung foot attached to the back so as the wax bulb pushed the stat disc open, it also pushed this foot against the port in the manifold to close the bypass. That's why you must have the correct thermostat, as if one is fitted without the foot it will recirculate coolant straight back to the pump instead of through the rad.
Incidentally, my late mk2 has a mk1 manifold but has a decent warm up time.....

Russ