MGB Register Forum

Week is been 3 years since I got the B out the garage.
3 hours to get it running the pooof, steam venting from the radiator cap.
I've tested the thermostat which is fine, flushed the rad and engine to ensure no blockage. Removed the stat and fitted the Moss adapter for stat removal also. When idling I can feel the top and bottom hoses heating up nicely so assume flow is ok. I've not got as far as driving out yet lol.
Run it up to normal temp on the gauge and steam is venting from read call again, grrr.
I'm out of ideas currently, any Suggestions?

There's quite a bit in your post I don't understand. Can you proof read and correct miss-typings?

What is a Moss adapter for stat removal?

Ian F

This is the adaptor
https://www.moss-europe.co.uk/blanking- ... j4012.html

What part is not making sense? I've flushed the cooling system checking for blockages, all clear.
Removed the stat to aid with overheating.
Yet still when the engine is idling at normal on that temp gauge the radiator is blowing Steam and water out.

Did you drain and bleed the radiator with the heater open so you don't get an air lock?

I normally associate the venting of water/steam from the cooling system as a symptom of head gasket failure. This over- pressurises the cooling system and introduced gases into the system.

There is a kit available for testing the cooling system for combustion gases, might be worth considering.

This kind of fault may not show up as a loss of compression in the cylinders, hence the test kit referred to above.

Please report back with what you find.

Ian F

I'm hoping it's not head gasket failure, when it was last used 3 years ago it had a new unleaded had fitted as they original leaded head had a crack in it.

I did drain the rad with top and bottom hoses off, I think the heater was on. What's is the process for filling the cooling system to clear airlocks?

Sorry but I'm new to this as I inherited the car from my late father 10 years ago and haven't personally needed to do any work one it yet.

Should have added it's a 1967 with rear elbow fed radiator.

James, I have a 72 BGT, very similar to yours, and with a very similar simple cooling system. I have never followed any particular process for refilling with coolant which I have done many times.Just leave the rad cap off, turn the heater on, and pour in the coolant (I always have had a thermostat installed). Start the engine and warm things up. Keep an eye on the coolant level in the rad and run until hot, topping up if necessary, and that's it - should be simple.
I have had over-pressurised cooling systems on B series engines (not my MGB) and others, and it's always been a head gasket replacement job.
I would get one of the kits I referred to if you have tried everything else. Replacing a head gasket is not really that difficult, but you must check that the head and the block are both absolutely flat and clean, and use a good quality head gasket - Payen or Elring.

Ian F

As a p.s. - you could try just re-torqueing the cylinder head nuts if there is any doubt about the installation of that replacement head. These nuts should be retightened after a few miles when the engine is hot.
Maybe not a permanent fix, but worth a try.

IanF

Thanks for all the advice Ian, I'll find out how it goes tomorrow as I'm moving the car out to storage