Overheating

Technical MGB discussion
Vic Butler
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Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Overheating

Post by Vic Butler » Mon Jun 15, 2020 7:49 am

No Charles. I can push it and I never leave the handbrake on in the garage. It's always in neutral with a chock in front of the offside rear wheel.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

Dave Wheatley
Posts: 146
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Mon Jun 15, 2020 11:00 am

I did a 50 mile round trip yesterday, and the temperature was significantly hotter than normal on N instead of half way between. It was a hot day, so that obviously didn't help.
My car goes well over N if I get into slow traffic, but never gets to the red. I run retarded on account of the unleaded.
I wonder if these cars have been marginal on the cooling since new.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

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Charles Farran
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Location: Warwickshire

Re: Overheating

Post by Charles Farran » Mon Jun 15, 2020 12:08 pm

Hi Dave,
In standard form the 4 cylinder engine cars are very tolerant of operating in warm climate conditions. Certainly the temp gauge rises when the car is held up in stop start traffic. I holidayed fro many a year in the 80's with the MGB (that i still have) in the south of France with no issues. I am aware that there are differences in where individual car's gauges read for any given temperature of the engine - i guess it's knowing what is normal for one's own car. My fan (touch wood) always kicks in before the gauge gets to red & about 2/3 across the range of the gauge.
More problematic is the life of the water pumps & the heater valve - but i believe the former is possibly due to the lack of regular use of our cars.
I'm sorry to hear that Vic hasn't found an easy solution to his overheating issue.
Cheers
Charles
1980 Roadster

Vic Butler
Posts: 559
Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Overheating

Post by Vic Butler » Mon Jun 15, 2020 1:52 pm

I hope to make a start in the next week or so. Hopefully I'll have the Land Rover back soon, now with heated windscreens and 2 speed wipers, plus a brand new bulkhead which was made in Doncaster the last week in May this year.
Some years ago the MG overheated and the cause was a water pump which had sheared the drive to the impeller. That's not the case this time unfortunately.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

Dave Wheatley
Posts: 146
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Mon Jun 15, 2020 7:08 pm

Charles, ta for that.
Good luck Vic.
Let us know how you get on.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

Ian Fozzard
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Joined: Fri Mar 27, 2015 8:18 am
Forename: Ian
Surname: Fozzard

Re: Overheating

Post by Ian Fozzard » Mon Jun 15, 2020 9:42 pm

Vic, regarding pressure tests/compression tests.

Just to be clear in what I was saying in an earlier post:

The compression test I was recommending was a cylinder compression test to check for a leaky valve.

The coolant test was for exhaust gases in the coolant to check for leaking head gaskets or possibly a crack in the head.

https://www.eurocarparts.com/p/euro-car ... gJ5LvD_BwE

Just in case of any misunderstandings😊

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear

Vic Butler
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Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
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Location: North West Hampshire

Re: Overheating

Post by Vic Butler » Mon Jun 15, 2020 9:55 pm

A compression test was done and all OK. I'd like to have a coolant pressure test done but with the position of the expansion tank tight against the offside inner wing I can't see how it could be done as there's no room to get the tester on to the expansion tank.
It was 6 years ago I fitted the cylinder head and I used a torque wrench that was long in the tooth to torque down the nuts. I now wondering if the torque wrench was accurate. I don't suppose the car has done more than 7/800 miles since.
I think I'll treat myself to a new torque wrench.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

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Charles Farran
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Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Overheating

Post by Charles Farran » Mon Jun 15, 2020 11:09 pm

Vic,
I trust all your coolant hoses are in good condition?
I have read elsewhere that if the hose walls are weak,under increased pressure at higher rpms the hose can partially collapse & restrict coolant flow & hence cause over heating.
I may have missed it but when did you last change the coolant if a standard anti freeze & water mix.
Your annual mileage is very low,so has corrosion created poor flow?
Just trying to find an easy & cheaper fix!
Cheers, Charles
1980 Roadster

Vic Butler
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Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Overheating

Post by Vic Butler » Tue Jun 16, 2020 7:53 am

Thanks Charles. The Kevlar hoses are in good condition and there's no problem with the flow as it doesn't overheat when I run it stationary.
I'm getting the Land Rover back this morning and then I'll make a start soon on MG head removal.
At least it's an easy job. There's someone further down my road who's got to remove the head on a 52 plate BMW and he's got all manner of electronic junk to deal with. In addition he thinks it needs new rings. The simplicity of MG ownership.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

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Peter Cresswell
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Location: Stone, Staffordshire

Re: Overheating

Post by Peter Cresswell » Tue Jun 16, 2020 1:38 pm

Hi Vic, given all the other things that you have checked so far, and the few miles your car has been doing is it a clogged up radiator that is causing the problem. The standard radiator is a bit marginal when the engine has been modified a bit so a new standard one might be the answer. Or try back flushing the one you have and see what comes out!
If the head is cracked and it is cracked into the water jacket, then you can usually smell combustion fumes in the coolant. It will also blow the coolant out of the system. This might only happen at higher rpm. It can crack elsewhere but in my experience that has little effect on the running and is only found when the head has been taken off for a top end overhaul.
Pete
1969 MGB Roadster
2020 MG HS Exclusive
2007 Mercedes SLK
Plus 34 other cars since 1965

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