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MG MGB Technical - Coolant Leak?

Hi, sorry if this has been covered before, but I couldn't find anything in the archives.

After a spirited drive in my 72 GT, and engine temp rising to mid way on the dial (N), very soon after parking up, I get a dump of cooling water from engine bay (about a pint)on to drive way.

I'm guessing this isn't normal? I've checked all hoses I can get to and core plugs, nothing seems to be obviously at fault, any ideas?

Just to confirm, after a relaxed drive, temperature dial 4/5's between "C" and "N", not problems at all???

Thanks in advance

Darrel
Darrel Laidler

Did the coolant come out of the overflow tube? It's not normal to lose coolant after a spirited drive. That said, if the radiator is over filled some coolant will overflow until the system has some expansion space at the top of the radiator.

Clifton
Clifton Gordon

If you fill it too full it will force some out due to expansion. With no overflow tank it'll spill onto the ground. When you shut the engine off the temperature under the hood actually rises and may force more out. Fill it to about an inch from the top. Leave some expansion space.
tom

Check your radiator cap for holding pressure. If the fluid is leaking from the filler neck, usually but not necessarily showing by staining the radiator face, there is a fair chance that the cap is not holding pressure. That may also expalin the temperature not reaching N, which you seem to be concerned about.

Parallel experience of mine recently. My cap was leaking to zero but looked perfectly good. Change of cap and all is good. Most workshops can do a quick check on the cap - should not cost anything if they know you.

Regards
Roger
Roger T

Dumping coolant *after* switching off implies problems. Dumping during warm-up is normal if it has been overfilled. Temp should be able to get right up to the start of the H section at the very least without losing coolant. Cap is the first thing to check (or simply replace if you can't find anyone easily to check the pressure), a friends 78 was doing much the same thing and I found his 15lb cap was only holding about 3lb.
Paul Hunt

Thanks for all the responses. I'll try a new cap and see how it goes.

Just to clarify, what is the correct water level. I have mine filled to just under top of rad, before it touches the neck of the filler pipe?

Cheers

Darrel
Darrel Laidler

Darrel - "I have mine filled to just under top of rad, before it touches the neck of the filler pipe?" That is probably too full. Instead of refilling the radiator each time it dumps coolant, leave it alone and monitor the level after a few runs. As long as the coolant is a 1/4 - 1/2 inch above the top of the core tubes, you have plenty of coolant and much more than that will be pushed out, usually after driving and then shutting the engine off. For more information on this and how to install a coolant recovery system, see the article, Expansion Tanks, Coolant Recovery Systems, and How The Cooling System Works in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ I am sure that Paul has covered a lot of the same information on his web site, the Pages of Bee and Vee at: http://www.mgb-stuff.org.uk/ Cheers - Dave
David DuBois

Thanks David. Read your article on Cooling Systems and found it very interesting. I'll leave the coolant level where it is after it last vented (just over the top most fin) and monitor it over the next few months.

Thanks again.

Darrel
Darrel

This thread was discussed between 22/05/2009 and 29/05/2009

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