Overheating

Technical MGB discussion
Vic Butler
Posts: 527
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 3:45 pm

This is what happens Peter.
At 70 in overdrive top on a light throttle it's OK, but when the engine has to pull up any slope the temperature gauge rises immediately. Back on the level on a light throttle, the gauge returns to normal. Leaving it ticking over the fan cuts in, the temperature drops and the fan cuts out. It's only when the engine is having to work that the temperature rises immediately.
It happened suddenly last year which makes me think of a slightly leaking head gasket.
It's easy to remove the head and see what is going on.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

User avatar
Charles Farran
Posts: 218
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Overheating

Post by Charles Farran » Wed Jun 17, 2020 10:05 am

Dave,

Further to my comments yesterday, as my MGB is on SORN pro-tem given that i only use my 2019 car once a week or so due to lock down, i tend to reverse the MGB out of the garage & run it on the drive for 20 -30 minutes with a mix of "reving & idling" every few weeks. It was a warm/hot day here yesterday afternoon & with the bonnet closed i monitored the heating gauge carefully watching for the first time that the cooling fan kicked in. This happened when the pointer on the gauge was just to the right of two tiny white dots i have in the centre of my gauge which more or less agrees with my comment made before about being 2/3 across the dial. - I guess living with the same car for nearly 40 years you get to know it!!!!

Cheers

Charles
1980 Roadster

Dave Wheatley
Posts: 132
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Wed Jun 17, 2020 1:07 pm

My fan comes on when the gauge shows just over half way.
But talking about fans, a previous owner has fitted a non standard fan on the crankshaft pulley. It's about a foot away from the radiator, so I can't see it doing much good. The electric fan is bout 10" across, and is placed to the drivers side of the radiator. It only seems to cool the oil cooler side of the radiator. Does this arrangement seem to be correct?
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

User avatar
Peter Cresswell
Posts: 658
Joined: Fri Oct 31, 2014 10:05 am
Forename: Pete
Surname: Cresswell
Location: Stone, Staffordshire

Re: Overheating

Post by Peter Cresswell » Wed Jun 17, 2020 2:07 pm

Hi Dave,
The fan should be an electric one mounted in front of the radiator. Are you sure the fan you have is fitted to the crankshaft pulley and not the water pump pulley? If it is the crankshaft I doubt it will do any good at all other than spray water off the road all over the engine compartment! Even on the water pump pulley it will be too far away from the radiator to do any good on a 78 car. I'd change it for the correct set up if I were you perhaps sourcing a good secondhand one.
Pete
1969 MGB Roadster
2020 MG HS Exclusive
2007 Mercedes SLK
Plus 34 other cars since 1965

Dave Wheatley
Posts: 132
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Wed Jun 17, 2020 2:33 pm

Thanks Charles for the reply.

Sorry, old age! Fan is on the water pump pulley.

Thing is I don't know exactly what I should have.

I have the bodged water pump mounted fan, and the small 10" electric fan which appears to work on the oil cooler part of the radiator. The main part of the radiator has no fan. Is the 10" fan normal?
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

User avatar
Charles Farran
Posts: 218
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Overheating

Post by Charles Farran » Wed Jun 17, 2020 2:39 pm

https://mgbforum.mgb-register.org/downl ... 76a1e7a392
Hi Dave,
Has a PO installed an after market electric fan like a Kenlowe? Your 1978 car would have the later radiator siting closer to the front of the car. The original set up was like mine in the attached photo where the fan was to the offside. V8s & some 4 Cylinder cars for overseas (i think the U.S.) had 2 fans fitted, but only one is needed in the UK for 4 Cylinder cars.If you temperature control is fine, which it appears to be then you can probably leave yours as fitted.(Particularly if the weather board is still in place between the front of the engine and the back of the radiator).
Cheers,Charles
Attachments
069.jpg
1980 Roadster

User avatar
Charles Farran
Posts: 218
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Overheating

Post by Charles Farran » Wed Jun 17, 2020 2:48 pm

Dave,
Just seen a further response after i sent my last post.
Does the original electric fan still work or has it ceased? If the latter, you have to remove the plastic fan off the motor spindle before you can extract the body of the electric motor from below the slam plate. When i refurbished underneath the bonnet i couldn't get the tiny grub screw out so removed the whole electric motor & fan together when the radiator was out & put it back in before remounting the radiator!
Cheers,
Charles
1980 Roadster

Dave Wheatley
Posts: 132
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Wed Jun 17, 2020 6:07 pm

Hi Charles,
Another senior moment here from me.

My radiator core is 2 sections, one a bout 6 or 7 inches wide on the drivers side, and the other takes up the rest of the radiator towards the passenger side. About 1 32nd" gap in the fins between them.

Now, I've misled you in that I assumed that the driver's side bit was for an oil cooler but on investigating this afternoon, I realised that the oil cooler lurks underneath the radiator, so presumably the whole of the radiator is for general engine cooling. But why the divide?

Anyway, another hot day, and a 10 mile run with no cooling probs, but where I live is V. rural, so very few traffic probs ever.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

User avatar
Charles Farran
Posts: 218
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Overheating

Post by Charles Farran » Wed Jun 17, 2020 6:15 pm

Dave,
Sounds like the rad is not an original type. It would be interesting if you could take a picture with a mobile phone picture of under the bonnet & post it up on the forum!
Cheers
Charles
1980 Roadster

Dave Wheatley
Posts: 132
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Overheating

Post by Dave Wheatley » Wed Jun 17, 2020 7:01 pm

Here's some pics.
WP_20190426_003.jpg
WP_20190426_002.jpg
WP_20190426_001.jpg
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

Post Reply