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MG MGB Technical - Overheating Auto 69BGT

Hello Everyone,

Just looking for some advice to remedy a problem that has just occurred and hopefully solve after the help from all you experienced people ;-)
My 69 BGT has just started to squeal on acceleration I think it could be the water pump but am not sure, yesterday I took a short 5 minute drive and noticed a short while after the squeal that the temperature guage had increased drastically, once back home I took a look under the bonnet and did not see anything unusual, I turned off the engine then a few moments later water was seen appearing under the car, on investigation it appeared to come from the radiator overflow / pressure relief pipe and must have had some mighty pressure as there was a lot of mess.

What I need to know is why would this happen as before hand all had been fine oil and coolant levels both physically and on the guage looked right. Would it be the thermometer suddenly jammed or something much worse?? All help and suggestions would be most appreciated.

Thanks Richard

Richard Geer

You've deduced the most likely culprit. But before you damn the water pump, make sure your belt tension is good. Push with your thumb on the longest span of the belt (between alternator and crankshaft pullies). You should only get between 1/4" and 1/2" deflection.

To check out your water pump - Take off the fan belt. Grab the cooling fan and try to wiggle it in all directions. There shouldn't be any play in the bushing. When you turn the fan, it should move smoothly. There may be a little resistance, but should not be a lot. These aren't comprehensive tests, but are tests you can make without taking off the pump.

If this hasn't turned up any evidence, run the motor without the fan belt on. (It'll be alright for a few minutes, just keep an eye on your temperature guage.) Is it still squealing? If not, then the problem was in your fan belt, water pump or alternator. Since you had the overheating, safest money is on the water pump.

BTW, while you have the fan belt off, check it for glazing or excessive wear. That squealing was probably the belt slipping, which takes a toll on them.

Lastly, current wisdom says it's better to have your cast iron water pump rebuilt than to replace it with the newer alloy replacements. I can't speak from experience on this one, but am just repeating what I hear.

Matt Kulka

Matt, the fan belt looked pretty sound on first glance but I'll remove it and take a closer look over these items tonight and report back with my findings tomorrow.

Thanks.
Richard Geer

Richard,

I had exactly the same coolant loss on my '64 but no squeal at all. I got a new replacement pump, replaced it and cured this issue as simply . I did not check the previous pump but it sounded good. HAve a look to anoyher post on this BBS " Running hot (Again) FIXED !!!" that muight help too.
Renou

Just snuck out to the garage, before the missus noticed me gone, and managed to take a look at the fan belt tension and condition, the tension could have been a little more tense and the condition was slightly worn, I have a spare so will replace it. There seemed not to be any play on the cooling fan.

However I also wobbled the front wire wheels and noticed some vertical play on the passenger side, I am now quite convinced that this may hold a key to the problem as this would have put much more strain on the engine and other components causing heat to build up quickly, possibly with the wheel wobble it may have caused brake bind??

One thing leeds to another:-0 if nothing else these great little classic cars provide great entertainment through puzzle solving.

Have to look into the wire wheel / hub issue and maybe that new set wont be too far off.

Richard.
Richard geer

This thread was discussed on 08/09/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.