MGB Register Forum

I think it is almost impossible to get all of the coolant out when draining the block, so any residual coolant may have enough of the marker gas in it to give another positive result?

I think just using the B now as you propose is the wisest course of action. Just make sure that the expansion tank is only filled to minimum when cold. (And retorque those bolts of course - when hot I think?).

Ian F

Yes, that's my plan. It seems impossible to have the expansion tank half full though. I took some coolant out of it but it just fills up again when the system gets up yo pressure.

I'll re-torque after a few heat cycles.

Cheers

Stu

Good luck and keep us posted!

Ian F

More driving today and still no leaks. I'm beginning to think there was never a problem in the first place and the leak was from the top hose on the radiator not being completely tight and me being fooled by the testing kit.

If that turns out to be the case at least I know the combustion chambers are free of carbon and that my engine is 40thou overbored

After further driving still no issues so the main thing to take from this is the combustion gas testers are only fit for the bin.

Thanks for keeping us updated. I must say I am a bit surprised, but I accept your conclusions of course. It certainly is very useful to know whether to use one of these kits - can you tell us which one you bought as I think there are several available?
If you have another vehicle (in good working order!) it would be very interesting if you could check the coolant with the gas tester and see what results you get.

Have you avoided the coolant loss issue by keeping the coolant level low in the header tank, allowing lots of air space for expansion?

Thanks again for the feedback. So many folk on the forum never provide any feedback so we aren't able to learn from the outcomes.

All the best

Ian F

I'm surprised too, and still not 100% sure the gasket is fine but it certainly looks like it.
The brand of the tester was Reld though my theory is that there's nothing actually wrong with the tester but the false positive is caused by very small amounts of oil contaminating the coolant. In my case possibly by using a not completely clean funnel to put the coolant in.

I actually re-used the coolant I took out as a temporary measure to avoid wasting a lot of new coolant if the head gasket was still leaking. I'll be flushing and refilling now it seems ok so will test again after that.

On the leak I think that all along it was the top radiator hose that was dribbling on to the overflow making me think the leak was coming from the header tank. I replaced the pipe clip and the leak stopped, so I suspect there was never a head gasket issue and I was too quick to assume there was based on the leak and the test result. The amount of coolant in the header tank seems to makes no difference.

I'll update again when I have replaced the coolant and tested again.

Thanks, Stu.

Hopefully the final update on this one. Last night I drained and flushed the cooling system with some Wynns radiator flush, and then flushed out with clean water. This morning I refilled with coolant and tried the Reld head gasket tester again and it as I suspected it remained completely blue.

So the lesson is don't trust combustion gas testers unless you have replaced your coolant first!

My B now warms up and keeps a fairly even temperature and doesn't get too hot even if left ticking over.

Thanks for all the input.

Cheers

Stu

That was quite a saga Stu, many thanks for keeping us informed!
Probably about time to put the B into hibernation for the Winter, so hope you get a few trips out before then.

Best regards

Ian F

Thanks - mine doesn't hibernate and will be driving all winter, though not too much when it's really wet.

Next job is to get my axle clonk sorted out.

Stu