engine coolant

Technical MGB discussion
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Mario60
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engine coolant

Post by Mario60 » Sun Oct 06, 2019 6:35 am

Hi, I am planning to change the engine coolant of my 72 B with a 50 50 mix. The radiator has no taps so need to remove the bottom hose and then flush with water. Is this the correct procedure? What do I have to do to ensure there are no air locks? Many thanks in advance for your help.
Ian Fozzard
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Re: engine coolant

Post by Ian Fozzard » Mon Oct 07, 2019 3:41 pm

Mario,
first of all I would recommend a workshop manual - either the Haynes one or the official MG one, assuming that you don't have one already.

Changing coolant is quite easy:

# make sure engine is cold
# turn heater to "on" to allow coolant out of heater matrix
# get a bowl to catch as much coolant as possible and dispose of it carefully. It is toxic but tastes sweet so is dangerous.
# remove bottom hose from radiator and radiator cap
# on the engine block below the distributor you should find a drain plug to allow the block to drain, although these are usually completely clogged.
# to be really thorough remove the thermostat housing and thermostat.
# flush everything out with a hose until water runs clear.
# fasten everything back up
# add the measured amount of coolant first, then top up with water.
# run the engine until hot with the radiator cap off and top up with water if required.
# after the first run check the coolant level again and top up if required.
You should have heat coming through the heater - shows no air locks, and the temperature gauge should read normal.

Hope this helps

Ian F
Mario60
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Re: engine coolant

Post by Mario60 » Tue Oct 08, 2019 9:09 am

Hi Ian

Many thanks for the procedure. I was thinking of also dismantling the heater unit as I do not think it is working correctly and from the look of it seems that it has never been out of its place. What do you think? Is there a link to how this should be done? Thanks

Mario
Dave Wheatley
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Re: engine coolant

Post by Dave Wheatley » Tue Oct 08, 2019 10:12 am

A quote from the very usefull website www.mgb-stuff.org.uk "Removal of the heater unit and especially refitting is frequently said to be one of those 'worst jobs' on an MGB".

I started to remove mine, and fortunately backed down before I was past the point of no return!
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
No modern!
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Charles Farran
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Re: engine coolant

Post by Charles Farran » Tue Oct 08, 2019 10:33 am

Hi Mario,
Removing the heater box to dismantle the box itself is in my view (having done so & many others) one of the most difficult jobs to do, made more difficult when the engine is still in place as you can't stand in the engine compartment to easily pull the box out once all the connections & mounting screws are removed.Before removing the box you need to determine what is not working. The original heater matrix was well made and provided you see no evidence of it leaking, may not be the cause of your problem - it may be the control cables themselves or the heater control valve on the side of the engine block.There is a lot of info on the internet (you tube) but in many cases the advice given is not clever. Paul Hunt's site is however extremely helpful - go to http:/www.mgb-stuff.org.uk.
When i did mine i consulted that & Paul via the BBS site with a satisfactory result - not withstanding that i still ended up with cut fingers & became an expert in key hole surgery which is required to ensure the heater flap control cable is connected correctly never mind easing the heater box out & then back into the aperture above the transmission tunnel.
Cheers,
Charles
1980 Roadster
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Charles Farran
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Re: engine coolant

Post by Charles Farran » Tue Oct 08, 2019 10:36 am

Hi Mario,
Dave's response came when i was drafting my one above!
Cheers
Charles
1980 Roadster
Ian Fozzard
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Re: engine coolant

Post by Ian Fozzard » Tue Oct 08, 2019 10:38 am

Mario,
Dave is correct - it is about the trickiest job on an MGB - not technically difficult but you do need universal joints on the end of your arms and plenty of lubricant!! I produced an article for the MGCC on how I did mine - I will try and attach the article here - if it's not attached send me a pm and I can email you a copy directly. My BGT is also a 1972 model so should be very similar to yours.
I suspect your heater will not have been removed before, but if you decide to do anything perhaps make sure of two things first:
1. check that the cables from the knobs are actually operating the valve on the block and the flaps controlling where the heat goes.
2. check that the valve on the block is not clogged up (remove it and look inside) and also that the heater matrix is not blocked - you can buy radiator flush which may clear any blockages.

[attachment=1]mgcc article.docx[/attachment]

[attachment=0]mgcc article.pdf[/attachment]

The two documents are the same but in different formats.

Ian F.
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mgcc article.docx
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Mario60
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Re: engine coolant

Post by Mario60 » Tue Oct 08, 2019 8:34 pm

hi all, sincere thanks for the tips and advice . As usual really helpfull

mario
Ian Fozzard
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Re: engine coolant

Post by Ian Fozzard » Tue Oct 08, 2019 8:36 pm

Let us know how you get on, and any further issues just ask,

Ian F
Mario60
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Re: engine coolant

Post by Mario60 » Wed Oct 09, 2019 2:29 pm

Hi Ian

I will, many thanks


Mario
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