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MG MGB Technical - replacing heater control valve

My heater (water) control valve is leaking on my 1980 MGB.

Is it necesary to drain the whole cooling system to replace the valve?

Any help would be appreciated.
Greg Alms

No. Some will inevitably come out when you remove the old valve/hose, if you don't want to lose it undo the bottom hose and drain some into a container for reuse, otherwise top it up with fresh afterwards.
Paul Hunt

Greg. There is water in the head which will leak out when you remove the heater valve. It will only drop to the level below the valve hole in the head. Hence, no need to drain the entire system, as Paul notes. A couple of observations.

First, there is a thread on replacing the current hex head bolts with bolts that are easier to get to. Socket head cap screws are the best solution, in my experience, and some of the others have recommended this.

Second, the heater control valve itself is a subject of much discussion and there is a great deal of information on them in the archives. The replacement valves are of variable quality and do not always turn on fully and turn off fully. In my opinion, the "Muenchasen Modification" has the minor draw back of not being capable of being turned on and off from the cockpit. It has the quite wonderful ability to be fully turned off in summer and turned on in winter. Bob has posted a great deal of information on this modification, but on this site and on his website. I am using my version of his valve on all three of my cars and recommend it highly. Turn it on in winter and off in summer. Les
Les Bengtson

What a great place for a heater control (right over the distributor). I don’t have pictures, but I can give you an idea. This will cost you a few points at the shows though. About 7 years ago I had this problem. I pulled the valve apart altered it so it was always open, packed it with a piece of aluminum, sealed it with silicon seal and put it back together. Now it looks original except it’s always open and doesn’t leak. Then I added a new one off of another car type (sorry don’t remember what) in line with the modified one. I didn’t place this one on top of the distributor.
Dennis Hill

"right over the distributor" - a design feature, so you get a warning when it leaks.
Paul Hunt

Paul,

As I recall my warning was backfiring, the engine quit and after getting it running again and home it had evaporated so I never saw what caused it. In my case I got two or three warnings before I saw that green stuff on my distributor. What can I say, I could have bought a Honda, I chose not to!
Dennis Hill

My wife loves the fact that I cant turn the hearer off completely cause it keeps her feet warm:-)

Cec
Cec

Ah, but with the Honda you get the main relay problem...
Paul Hunt

Think the Triumph TR?? heater control valve is the one to go for, if my memory serves me correctly.
Fred


Thanks to everyone who responded. I replaced the heater control valve tonight and I'm back on the road.
Greg Alms

Hi Fred
Its not the TR5/TR6 it has the same useless valve as the MG except it screws in instead of bolting on
Ron
r algie

This thread was discussed between 17/05/2003 and 23/05/2003

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