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MG MGB Technical - Heater Valve

I am a longtime MGTD owner, and a new (1 year) MGB owner. Because it was a warm day, I decided to take my B out for a ride. Because I did not use the battery shut off valve this winter, I needed to jump p start it. So far, so good. I had used the choke for the cold start and the engine fired up quickly. Unfortunately for a completely different reason, I was pulled away for an emergency before I turned off the choke so the car was running at high revs (3,000+) for no more than five minutes. When I returned the coolant was on the floor and it looks like the heater valve was leaking ( the heater was left in the "on" position from the last time I drove the car in November). When I first purchased the car, the heater valve failed because I was told the car had been sitting for awhile, so we put in a new heater valve. I have a dumb question (actually am hoping against reason) - Is the valve toast, or does it have an overflow mechanism? if the answer is that it's toast, I had searched the archives and saw references to using other valves instead of the OEM valves. What's the consensus?
Mike Iandolo

Sounds like the valve is dead--just get another original one---keep it simple
The main issue here is that the choke speed needs adjusting, there shouldn't be a situation where engine revs get to anywhere near 3000rpm on the choke, it should be at or just above normal idle speed----The job of the choke is to richen the mixture not to rev the engine like that
William Revit

Thanks William. I was thinking that I would need to replace it. It looks relatively straightforward. I will definitely look into the idle speed when I get the new heater valve in.
Mike Iandolo

They don't last anywhere near as long as the originals, the V8 (so far!) has the one it came to me with 26 years ago but the roadster was first replaced 20 years ago and again 10 years ago so may be due for another failure. I found I could undo the screws on the originals with a ring-spanner but the body of both replacements is too fat. There are two types available in the UK - what are described as 'OE' and 'aftermarket' but even the OE one I bought for the second replacement was the same. I ground the edge of the ring spanner down, and a 1/4" drive socket fits as well but needs a square bar bent at a right-angle to fit under the wider part of the valve to drive it.

The fast-idle speed is set with the engine warm and the choke pulled just before enrichment starts, and that should give about 1500rpm. With my roadster HSs if I left the choke pulled fully then it would race like you say which is why I push it in about half-way immediately it starts and that gives enough enrichment as well as fast idle.

But with the V8 HIFs it needs full choke for a few seconds and only gradually reduced from there, and if I set the fast idle as per the manuals then that would race as well, so that is set backed off from book.
paulh4

Mike,
an appropriate Driver's Handbook will give you lots of driver and servicing, maintenance information including setting the carbs, though not the easiest explanation (IIRC). You probably know that pulling the choke cable out for the first part gives 'fast idle' without enrichment which comes with pulling the choke more.

For the heater valve you may already know with the cable and valve you can set it to get either fully closed or fully open but not both (and movement between the two of course) so you chose which setting would be best.

Have a look at the (John Twist) University Motors videos and also paulh4's excellent comprehensive and very informative site. - http://www.mgb-stuff.org.uk/hammertext.htm

Nigel Atkins

Mike,

When fitting a new heater valve , blow through the feed pipe & then progressively close the valve until it is air tight. Then mark on the valve body where the lever in the body has got to. There is nothing to be gained from proceeding beyond this point in terms of stopping any water flow when connecting up the cable for the off position. This saves undue pressure on the internals of the valve when in the closed position, which shortens it's life span.

Cheers,

Charles


Charles9

Good point. Attached shows the off and max points of a pal's replacement valve. Closing it tighter may bring forward diaphragm problems.

People say that the existing valve doesn't open far enough, but on both mine I have to turn the control back past the WARM mark before the temperature starts reducing, and that's only inching it back and leaving it for several minutes to stabilise, these do take time to cool down even when turned fully off. That indicates to me that the flow is putting more heat in than the matrix and fan can get out, I get 60C out of mine on a 10C or lower day, coolant input temp 83C, heater output pipe 65C.



paulh4

Mike. Details on how to convert an original style valve to the "Muenchausen Heater Control Valve" were still on the internet the last time I bothered to check. Bob Muenchausen used to visit this site quite a bit many years ago and descriptions and photos may be in the archives-if you can find them. I have used this valve for over 20 years, on four vehicles, with excellent results. Bob's basic valve has to be adjusted from the engine compartment (not a big thing in my experience) but some of his later experiments were adjustable from the passenger compartment. You might do a internet search on the subject and see what you think. I have never had to replace one after it had been made and installed.

Les
Les Bengtson

Gentlemen - thank you for your comments and suggestions. My MBG is a 1980 Limited Edition in BRG with tan interior. It is a great car in excellent condition. No rust - has a new coat of paint, everything works well except the electrical, but only needed to replace the coil and the heater valve. It has plenty of power to make the drive fun without getting into trouble. My other vintage cars are the 1952 MGTD and a 1987 Land Rover defender. The MGB is much more sophisticated than the TD (which really doesn't have much under the hood) and the Land Rover (which can be fixed with a 1/2 inch wrench). While the MGB can easily cruise at 60 mph, there other two cars can to even reach that speed.
Mike Iandolo

Ah, the coil! Make sure you get the right one.

Originally chrome bumper cars used a 12v coil with a 3 ohm primary, and rubber bumpers used a 6v coil with a 1.5 ohm primary because they had a ballasted ignition feed. But later North American spec with the factory 45DM4 electronic ignition used an even lower resistance coil without the ballast as that system uses variable dwell which means the coil can take a higher current without overheating.

If the coil is not matched to the present ignition system and wiring you will either get weak sparking or an overheating coil.
paulh4

Yes, they are unreliable and corrode up. I had one give up on me. For a while I just used the flanged elbow from a Marina 1.8, which was minus the valve. Can't say it made much difference to the heat in the car with it permanently on. Then the elbow separated from the flange! Bought another pukka valve, which again failed. The heater didn't seem to work very well anyway, and seemed to leak, so in the end, I blanked off the hole in the head, blanked off the take off on the bottom hose, took out the heater, putting a plate over the hole. Now got an oil catch tank there. OK, it never gets that cold in Wiltshire (or hot for that matter). Demist with a cloth. I drive it year round (eighty mile round trip yesterday). Hood up and dressed appropriately for a gentleman of a certain age - great!


Peter Allen

Peter well done to you driving your B all year round.

When I had my 1800 GT I done something about the heater, forget the details now, and I was pleased with the improvements but a mate said "yes but wait until winter". He was right, it was warmish but not hot. I think it must be the design and cold air getting in the cabin from the fresh air flap even when closed and other ways into the cabin.

The Spridget heater with small cabin gets too warm, I keep the heater turned off most times even through winter as my wife doesn't want it on as it too hot on her feet (I have a metal parcel shelf over the passenger's footwell) and I don't like the heat directed to the screen as it gets my head too warm with the roof up and is a waste of time with the roof down for screen.

I do sometimes have the heater on my legs if I have the roof down in the cold but of course as it's just a tap on top of the cylinder head it means the bonnet has to be lifted and tap turned to switch on and off and it's either hot or not nothing in between. It's not been on at all this winter.

Nigel Atkins

Mike. Why was your LE repainted in British Racing Green? I only ask because all of the factory cars were black in color and mine had a black interior. Do you have the Heritage Certificate for your MGB? If so, does it list "Black" as the color it left the factory with? I have seen several "Limited Edition" cars that did not start life out as an LE. If you purchased the vehicle as a Limited Edition, you might want to do some checking to see what you actually have. Ken Smith, quite literally, wrote the book on the MGB LEs and you might wish to obtain a copy for your book collection. But, be aware that almost all of the parts that made a Limited Edition a true LE are currently available from the various parts suppliers. This includes the "Limited Edition" plaque that is on the cover of the glove box. There is only one item, a decal, that is not available and was specific only to the Limited Edition models.

Les
Les Bengtson

According to Clausager the first LE for California was chassis number 492129, the other states 492107 and Canada 492071.
paulh4

Les,

The car was definitely repainted as part of a total restoration by one of the previous owners. I was told by the seller that it was a limited edition. I will check the serial number as Paul suggests. I will also look for other documentation. I attached two pictures that I took las fall just after I purchased the car. Thanks.





Mike Iandolo

Mike. It looks like a very pretty car. My concern is whether the "Limited Edition" claim influenced the selling price of the vehicle. If so, it would be desirable to know whether it actually is an LE model or not. If it is simply a nice car and it does not matter whether it is an LE or not, the matter becomes less significant.

As I noted, the Limited Edition model was only available in the color black and all that I have seen have had a black interior. The British Motor Heritage Institute Trust has all (or most) of the records of the former MG Car Company and for a very reasonable price will send you a nice certificate showing all of the information they have on your automobile. It is a good investment for anyone who intends to own the vehicle for a longer period of time. It is mandatory for a collectable vehicle. And, MGs in general, and LEs in particular, are becoming very collectable when in good condition. MGs which brought $10K twenty years ago are bringing three times that amount now and the prices are going up over time.

Paul's information on the first vehicle sold as a Limited Edition in each of the three market areas is useful. Any vehicle made before those numbers would be suspicious if it were claimed to be an LE. However, the entire series of slightly over 5K vehicles was made along side all of the other MGBs made between 1979 and 1980--the LE cannot be identified by any special form of serial number/VIN. They were jumbled in with all of the rest of the cars produced.

If the Heritage Certificate shows the original colors as being black exterior and black interior, there is an excellent chance it is an LE. But, from the photos, I believe you have a very nice looking MGB with certain commonly available Limited Edition parts added onto it.

Les
Les Bengtson

Les,

My information says the car was manufactured in September, 1979. The last six digits of the VIN are 504548. The engine number is 18V883AEL 043888.

I bought the car from a reputable shop on consignment. The seller said the car was repainted and new upholstery was installed. I actually have the papers from the bodyshop that did the work and respray in 1997. The seller said the alloy wheels and steering wheel were typically part of the LE package.

I really don't care if it is an LE or not. I did not pay a premium. I actually am not a big fan of the LE decals, if I am completely honest. Can they be removed without harming the paint finish?

At the risk of angering any purists out there, I am seriously considering doing a conversion from the rubber bumper to the chrome bumper. I realize that the rubber bumper cars sit higher than the original chrome bumpers, so any expert will know that it was a conversion.
Mike Iandolo

Chassis number clear enough, and that engine number also puts it right at the end of production. I can't really see someone trying to falsely represent it as an LE, but have it painted green!

All LEs had those wheels and either black or beige trim. It has the dash plaque and the correct steering wheel, but doesn't seem to have the black rubber air dam that fitted on top of the metal valance under the front bumper.

Over here bumper conversion often includes lowering to CV height as well. But one glance at the interior shows it as an RB, and the suspension and handling have been compromised.

Sell it and get the car you really want, but being green will reduce its value as an LE.
paulh4

Thanks Paul.

You make a good argument. Converting the car to chrome bumper destroys its authenticity. You certainly have me rethinking this. I really like the way this car drives so I don't want to sell it. However, since I have gotten use to the look of the rubber bumper, maybe I will not do the conversion. What I am now thinking is that the decal (which I never really liked) announces very loudly that this is a MGB LE with the wrong color. If I remove the decal, then it is a standard rubber bumper MGB LE. Do you know if the decal can be removed without harming the paint?
Mike Iandolo

I've seen some removed by carefully warming them with a hair dryer, but don't know if that works with these.

Would announce itself as a standard MGB of the era, not an LE though.
paulh4

Mike,
I don't know about the decal removal, it might depend on who put it on when. I do wonder, depending on how/where the car has been kept if removing the decals might have the paint below a slightly different colour.

It's your car if you want to remove it's fine, the fact that you are driving the car makes a lot of sense to me so you want to be happy with it whilst you are.

The number of people now that know what an MGB is miniscule, of those the ones that know about LEs would be a tiny fraction. If any one asked me about the colour or told me it's "wrong" then I would explain to them that it's vey special LE as it was originally made for, and presented to, the Irish Royal Family.
Nigel Atkins

Mike. I do not see any need to make up a story about your car. It is a very pretty car that someone added a number of new, commonly available parts to.

As to the striping, I would want to know what system of paint was used in the repainting and would ask the advice of a good paint shop on how best to remove the decals. I recently had a discussion with a "restorer" of T-Series cars who told me he used a "clear coat-base coat" paint on his "restorations". One can only hope that none of the people who have him do work are looking for a "show car" for exhibit a the better quality car shows.

The "Limited Edition" dash plaque should be centered between the lower edge of the glove box lid and the button for the lid release, both horizontally and vertically. Having it in the upper left hand corner indicates something is amiss.

As to rubber bumpers, the RB MGBs were much better cars than many give them credit for. I purchased my first one in 1979 and it worked fine for high speed touring on the German Autobahns. It is also better than my CB car when going over curbs (in and out of driveways), going over speed bumps, and in general in town and cross country driving. A much better laid out interior, more comfortable seats, and bumpers which are little different than commonly encountered on modern cars make the RB MGB, in many ways, a more desirable driving vehicle than the CB counter part.

Les
Les Bengtson

Thank you Les, Nigel, and Paul. This afternoon, I am seeing the gentleman who sold me the car and I will ask him if he knows anything about the paint job. All of you have been very helpful.
Mike Iandolo

No problem, thanks for reporting back.
Nigel Atkins

This thread was discussed between 07/03/2022 and 15/03/2022

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