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MG MGB Technical - Heater valve problem

I'm about to replace my 3rd heater valve in about as many years.

The first one started leaking around the gasket where it attaches to the engine block. It was over 25 years old so I didn't complain.

The next one (about a year later) started leaking out of the actual valve itself. I figured it was just bad luck so I replaced it again.

Now it's a little over a year later again and the latest one is also leaking out of the actual valve. Leaking is an understatement. I stop the car and lose almost all my coolant in a few minutes. It leaks mostly if the valve is in the completely closed or completely open position. Anywhere in between and it only drips slowly. So for the last couple of weeks I've left the heater valve halfway open and just topped up the coolant every day.

I've bought yet another heater valve but before I install it I'm wondering if I'm just asking for the same thing to happen again. Considering I rarely (if ever) change the setting, would I be better off putting some sort of plumber's tap in place and disconnecting it from the cockpit controls? I've heard of people doing something similar. Is it a good idea?

Any help would be appreciated.

Regards,
David
David

I have had very similar experience - had to replace a valve every spring for 3 years. The last one has lasted about 3 years, but I attributed it to the fact that I decided never to adjust it. I have left it on its hottest setting all this time (I need the heat in the spring and fall). I just turn the other knob to "off" to stop the hot air from coming into the footwells or the defrosters in the summer. However, I just may have gotten lucky with a good valve, based on yours failing despite not adjusting it.
I have heard there are 2 qualities of valve available, one that is about $40 USD, the other that is $70 USD, and the more expensive one lasts as it should (genuine Smiths brand?).
Check out this link on Bob Muenchausen's website:
http://www.cibolas7.net/12245.html
If you are not concerned about originality, there is another page on Bob's website that talks about how to make your own valve:
http://www.cibolas7.net/12272.html.
Hope that helps,

Erick
Erick Vesterback

Thanks for that. I thought I'd seen that article before about making your own alternative valve. Now I can read it again and make my mind up if it's the best way to go for my problem.

I was told by my supplier (Heritage MG in Sydney) that the original valve is no longer available. I'll have to check with the US supplier mentioned on Bob's web site and see if I can get an original Smith valve in case I want to put the car back to original state one day.
David

Check this link http://www.cibolas7.net/12299.html for an alternative to the stock valve. I used a different approach, getting a valve at my local auto parts houses that I could adapt in our MGB. Cheers - Dave
David DuBois

David, I have found a lot of the new replacement heater valves from the usual suppliers are not assembled properly and are loose and leak. I have had to reclamp the exterior plate to the body by puting the valve in the vice and reclamping the tabs one by one. That did the fix.
Barc Cunningham

I'm going to put the new valve on as I've already bought it and for the sake of $40 (roughly what I paid) I can't be bothered driving all the way back to the supplier.
I'll have a look at the old one and try and figure out what the problem was. Maybe it was just the casing was loose.

I'm definitely keen on the alternative ideas if/when I have to deal with it next time.
I think I'll first look for the original Smith part next time, but if I'm unlucky I know a few plumbers who can hook me up some fandangled brass/copper fittings with the big chunky lever. I'll feel like I'm opening/closing the flood gates on the Warragamba Dam, but at least it won't leak.

Thanks again all.
David

There is a seller in the UK that has the valves made to the original specification. His name is Ashley Hinton. If you need another he comes highly recommended. I have no affiliation with this company.

http://cgi.ebay.com/MGB-MGB-GT-MGA-TVR-1800-HEATER-VALVE-CONTROL-ORIGINAL_W0QQitemZ290269975153QQcmdZViewItem?hash=item290269975153&_trkparms=72%3A1207%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3911.c0.m14
Frank Mooring

Rubbish parts. If you can get a New Old Stock or one built to the original quality as I seem to have done just a few years ago you should be fine.
Paul Hunt

David,
I had the same problem. Three in two years. The rubber in the new valves is no good and perishes.
My engines a V8, but runs no hotter than the 1800.
I'd suggest putting a hose outlet on the engine as per Bob's article and using an in line, cable operated, ball style, heater tap (or valve).
I got mine from East Coat Auto in Melbourne. It cost about $60. It looks identical to the RV8 one. It is a half inch valve so you'll need to use a half inch hose fitting on the engine and an adaptor on the heater. In My case I just pushed the half inch hose over the top of a greased remnant of the orrigional hose. Can't ever leak because of the ball valve construction, is easier to operate because you're not pushing against pressure. It has an intermediate slot in the ball so you can have it on "medium" if you want. Full open it lets way more heat through and of course when it's closed, no heat at all.
You do need to set it up with the cable pointing away from the flow/engine, otherewise a little gets though. If you hunt the archive theres a picture i there somewhere.
Peter

I may be way off base here but why not just take the valve apart and replace the rubber seal? Basically all you need to do is drill out the pop rivet and turn the top and it all comes apart. A few years ago there was much discussion in regards to the modern valves not letting enough hot water through and at that time there were articles describing how to take it apart and rebuild it.

Just a thought.

Brian
Brian Smith

They won't sell you just the rubber bit. There's a New Zealand guy who managed to substitute a bit of gum boot. However it must have restricted the flow a little.
Peter

The OE seal is a convoluted shape so the centre can move up and down relatively freely while the outer ring is clamped tight. A flat piece of rubber will have to stretch downwards to close the valve, but paradoxically when flat it will sit *higher* off the main valve seat than the OE seal. However this won't allow any more coolant through the valve, as that is governed by the inlet and outlet ports, which are about half the diameter of the main valve port.
Paul Hunt

As Peter correctly suggests, the rubber diaphragm is not available. I'm the chap who in 1996 replaced the diaphragm in my '68 MGB with the piece of gumboot. It's still going strong!!! It was an old farm gumboot with a rbber/canvas laminate in the boot's leg section. I cut out a circle of the boot material, and left the original diaphragm piston in place. I needed to close the housing with all my strength. I was concerned with possible restriction in coolant flow brought about by a stiffer material, or imprecise following of the piston in the pump, but I figured the pressure of the coolant would hold the diaphragm open when the tap was open. It worked for me with absolutely no impairment to either heater operation, or engine cooling. Try it. What have you got to lose.
R P Shoebridge

RP,

You are a man after my own heart. I drove a Saab 99 for years that used the Triumph TR7 engine. It had the same PCV valve as the MGB.

When the diaphragm in the PCV failed, I replaced it with a thin latex glove. It worked for years, but being conservative, I always kept a spare.

Where did I keep the spare? In the glove box, of course!

Charley
C R Huff

Well done Charley
I too keep bits and pieces thinking that one day I'll find a use for it. The unfortunate result is that my 'bits and pieces' box is quite full, and every year I have to clean it out. No room at all in an MGB glove box for much except the CD player user manual!
Regards, Ray
R P Shoebridge

Clean it out!? Shame on you, if you haven't found a use for something yet you haven't kept it long enough.
Paul Hunt

This thread was discussed between 30/10/2008 and 11/11/2008

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