We just purchased a 1960 MK2 (originally a 2.4 now a 3.8) manual with OD. There is no coolant heater control valve. A search revealed that early MK2's indeed did not have one that the cabin temperature must have been regulated by the heater box flaps and controls.

Well my flaps and controls are apparently all stuck. So during the first few drives in the care we are getting heat. I have lived in Florida now for 33 years and hardly ever remember using the heater in any of my cars.

Thus at this early point instead of taking out the heater box for refurb, I just want to eliminate the heat. So we see two options.

1. Just eliminate the coolant from flowing through the heater by detaching the inlet and outlet pipes and connecting them together, bypassing the heater core altogether..

2. Install some sort of valve on the inlet to the heater. I have a manual thumbscrew valve which I can easily install. By the way which one in the inlet pipe?

Installing a valve leads to a broader question regarding flow. We have a 1970 BMW 2800CS coupe. It too relies on the flaps in the heater box determining the cabin temperature. So we have the same problem with it. There has been some debate as to the installation of a control valve to throttle or stop the coolant flow. The reason is the coolant flow return goes into the back of the head, and some say the flow is needed for proper head cooling, as the coolant flow is always flowing through the heater core. So by blocking the flow would impede proper cooling of the head, that's why BMW did not provide shut off valve.

Doe the XK engine have a similar flow path? Sorry I am just learning the car, hence my initial ignorance. Apparently on later MK2's that have the heater valve, one could shut off the flow entirely to the heater without affecting the engine cooling overall. Has there ever been any conversation about always have a flow path whether the heater is connected or not (my option 1) with regard to engine cooing?

Thanks
jjsandsms

 

Just go for option 1 for the immediate future. The engine coolant does not rely on the heater box being part of the engine cooling system flow path.
I live in a climate slighter warmer than Florida and heater systems are commonly blanked off/ turned off for summer and might be got operational for winter primarily for defogging windscreens.
Cheers

 

i used your option 2 in my 1953 MGTD...

i measured the inside diameter of the inlet hose, although i don't believe that it mattered whether inlet or outlet was used, to the heater core, which sits inside the cabin. i then bought an inexpensive plastic valve that fits that dimension. it possesses two barbs, one at either end. i also purchased two hose clamps. i proceeded to cut about three inches out of the hose that sits within the engine compartment and inserted the valve. the plastic valve and the clamps weigh about the same as the length of hose removed. so there is little tendency for the apparatus to sag when affixed.

subsequently, i turn the valve on in the autumn and turn it off again in the spring. the entire heater sits inside the cabin on the TD and has doors and a multi-speed fan. various combinations of valve, doors and fan give various amounts of heat. ...works a treat!

 

When they work, the original Jaguar systems of the Mk2 and S type should cut off the flow completely. Either option is fine, I'd take the easiest and see how it works. Longer term, if you're not worried about originality, an electrically operated valve would be cheap, effective and convenient. At least one XK owner has gone further and added an electric pump to increase the flow of hot water through the heater when it's required in cold weather.

As for BMW, I really don't know. Relying on the heater flow sounds like a crude improvisation. I'd have imagined that they would have used a valve to redirect the flow to bypass the heater rather than leave it open. Still, some of the BMW engine failures that have been reported in recent years go seriously against their reputation for excellence.

 

Well fit one from a later Mk2. Slider, Bowden cable, valve and all. They are readily available. It already has a 3.8 engine in it.

 

That is the logical solution. The only thing against it is that it operates off the same Bowden cable as the hoth-cold flap, which means it needs some careful 'synchronisation.' Given the stuck flap and the necessity of making up a bracket, it could become a touch painful. It may be one of the reasons Jaguar switched to vacuum operated valves and flaps on the S type and later cars.

 

I know & I don't see that as a major drawback. But then I don't have to do it.

 

You could use a Series 1 E Type lever assembly, it has one cable for the flap and one for the valve.

 

If the flaps in the heater box are seized and cannot be opened and closed using the Bowden cable that is there for that purpose, instead of installing a second, why not redeploy the existing Bowden cable to open and close a valve inserted into the flow of one of the water pipes. It would still use the Hot and Cold slider handle in the cab and give you hot and cold air. That said the cool air is still coming from the engine compartment so it is not so cool.
I would pull the heater box and get the flaps working again. A bit of penetrating fluid and gentle back and forth movement and the flaps should free up. You will find all the foam seals will have perished so it will give you a chance to replace them and seal the heater box off from the cab with the flaps.

 

Getting the old system to work was never a problem for me or my father. I think there are instructions in the service book, but I know that others have found it difficult. Since the OP may have other more pressing problems with the new car, even if it's only testing it to find what he wants/needs to do to it, a quick and dirty fix seems appropriate for now while he works out what he wants to do with the heater and other aspects of the car (like the axle) in the longer term. There's also the question (for him) of whether he wants to aim for original or make updates - it's already upgraded in the engine department. Where the Mk2 heater is concerned, there are more opinions on uogrades than cars and most of them offer some degree of improvement.

 

My first objective is to get the car running safely and reliably. As I mentioned right now we just want to eliminate the heat in the cabin so I will probably just bypass the heater entirely. My longer term fix is to yes pull the heater box and get flaps working, unseize the cables, an will probably just install a manual valve initially. As mentored heat is not a big priority here in southern FL.

AC will be going into the car long before we ever pull the heater box, although searching I have found some options to replace the heater box as part of an A/C installation, but that is for another thread when we start on that.

Thanks to al for the suggestions. I really am impressed with the knowledge and the rapid response all of your have provided.

jjsandsms

 

The OP/Bill's bypass is the obvious quick fix for now.

"1. Just eliminate the coolant from flowing through the heater by detaching the inlet and outlet pipes and connecting them together, bypassing the heater core altogether."

In Florida I'll bet it stays that way for a very long time. (We have offices in Coral Gables that serve the Caribbean & Latin America with it's muggy climate). You have other priorities.

 

jjsandsms
If you ever go to sell the car to someone in a colder climate with all the heat disconnected, it may drop the value.

 

Sounds like Lyons when Mk2 heaters were criticised in the US as somewhat ineffective. ~ "You should wear a coat son".