Refuse to let Winterís grasp keep you out of your LBC this year?
Canít get your heater to, well, heat?
Flushed your heater and cooling system Ďtil youíre blue in the face?
Big money says your heater problem is the valve on the engine that opens to let water into your heater. These little valves seem to be common to most BMC/BL cars, but especially on MGBs and MGAs. And equally troublesome is unbolting the valve from the head. There just isnít enough room to get a wrench in there and rotate it too.
The easy way to fix it without removing the valve assembly is to: (But first, drain about a gallon of antifreeze out of the radiator. And always work on a cool engine!)
1. Locate the pop rivet that holds the two halves of the valve together.
3. Rotate the valve body slightly until it disengages from the part of the valve still bolted onto the block.
4. Pull back the disengaged half of the valve.
The whole process should take less than an hour. I've done it more than once, so it's a common enough problem and easy to fix. The problem comes when someone who doesn't know about this starts messing around, and flushes or replaces everything in the system but the valve. Things get expensive then. Iíve even seen people write in stating that the hole in their head was never drilled out at the factory, when it was just completely clogged! In the worst case, your head may need to be hot-tanked.
These valves are always marginal at best. They are also one of the only aluminum parts on a cast iron engine, and the electrolysis reaction causes the paste to form when 1. the antifreeze mixture is weak, and 2. the chassis ground is marginal. The heater control cable can be a secondary ground if the engine - to - frame ground strap is loose.
And speaking of the heater control cable, before you even start this procedure, ensure that you are getting full travel between the control knob and the valve. It has to open properly to work.
The heater core is usually a nearly bulletproof unit with ample internal passages. I found the nearly 40-year old core on my MGA to be fine, so unless it is leaking, it's probably not the problem.
(theAutoist NOTE: &, if you want to modify your control valve for even more water flow, click here to go to Bob Muenchausen's site.)