Morris Minor Owners Club

Hello there,
I set out yesterday to investigate a water leak which I'd assumed was from the radiator but it turns out that the end of the thermostat cover which joins the hose from the radiator has corroded and turned into a crumbly mess. I've got a new cover but the old one isn't budging. So far I've tried tapping with a hammer to try and free up the bolts, given it several soakings of WD40 and similar and even tried to pry it with a flathead screwdriver (Result - the end of the screwdriver snapped and is wedged in the gasket ).... Any tips would be much appreciated!

If the housing is scrap - and it certainly sounds like it... Simply run a hacksaw through it a few times next to the studs but be carefull not to cut through to the cylinder head

That sounds like a plan.... how do I then get the remains off the studs? Will it unscrew with molegrips maybe?

Destroy the old one completly

But what about the studs? Are they part of the cylinder head or can they be replaced too?

The studs can be removed and replaced.

Try to avoid damaging the studs. If they break they can be a pain to remove and also try to avoid damaging the surface of the head.

Smash the old one with a chisel and heavy hammer. Fit new studs if in any doubt. It's a good idea to run a drill bit down the stud holes in the new cover - easing the holes out slightly - and smear copper slip (or even just grease) on the studs when fitting the new cover.

As Mike says try and avoid damaging the studs - run the saw blade down either side of the stud, if possible just away from them.

The remains of the housing should just fall away as they usually seize around the studs with corrosion.

New studs are simply screwed in but you need to go carefully when you remove the old studs - unscrew them a bit at a time and if theyre stiff, then screw them back in a little and unscrew again with some plus gas- repeat until they free up.

When you fit the new housing a smear of copper grease on the studs will help them to free up when you next have to do it!

Taupe

Try a brass housing, I never have any trouble with corrosion since fitting one.
Minor developments used to sell them.
It's been mentioned before but don't know if they are still available.

The alloy ones are fine - IF decent antifreeze is maintained in the engine.

Thanks all for the tips and advice, the pesky cover is now removed thanks to a little bit of cutting next to the studs with a dremmel combined with prying it up with a heavy duty flat-head screwdriver, studs are intact and no damage done to the cylinder head

Nice job! It's one of those that needs a mixture of brute force and care.

Don't forget to Copaslip or grease the studs, it'll be a piece of cake for the next person, which might be you!

bmcecosse wrote:The alloy ones are fine - IF decent antifreeze is maintained in the engine.

Not all of them, the new one I had was corroding badly in less than a year snd that was with Bluecol antifreeze. It also seized up on the studs.....

A good tip if you replace the studs is to put some thread sealant or hylomar on before screwing them into the head - this reduces the tendancy for fluid to leak up between the studs and housing which is the cause of the corrosion.

Not all of them, the new one I had was corroding badly in less than a year snd that was with Bluecol antifreeze. It also seized up on the studs.....

That's quite worrying!! One of the main reasons to use antifreeze all year round is to stop that kind of thing
You should only expect to see a seriously corroded or crumbled thermostat housing if the car has been run without a decent antifreeze dose.

Yes, it may have been a 'bad batch' as it didn't have the same smooth appearance or quality of old stock. Corrosion took the form of a sort of white effervesence and pitting to the surface. This was a few years ago so I think 'new' new ones are probably OK as nobody else has reported this since.