Hi,

I recently replaced a defective water valve in my xj8 in an attempt to get the heating/cooling system working properly. I have had the coolant lines "bypassed" for a year or so now....

So before I put everything back together, I tested the valve and the pump to make sure they were working properly. The water valve solenoid moves the valve plunger down (the bad one I pulled didn't move at all, the rubber seals had swollen up) and I tested the little pump. Put 12V into it and it spun fine.

So I *kind of* have heat now..... however I am experiencing a problem, as noted in other threads here, where I have intermittent heat.

It is pretty simple, with the car fully warmed up if I am at a complete stop (idle) I get HOT air coming from the vents.... if I am cruising down the road, it is luke warm (at best).

So I am wondering, is it possible to have a aux heat pump spinning/running and still experience the intermittent heat issue described by others here?

Or is there something else going on here I should look at?


Thanks for any insight.....

 

Does your temp gauge stay at constant half scale? Your thermostat may not be controlling. Are you sure you have the hoses routed correctly?

 

I'm pretty sure the hoses are correct. I used the flow schematic from JTIS to hook everything back up.

My temp gauge does in the middle.....that is not swinging up then down constantly.

 

Have you tried bleeding the cooling system of all air pockets? Sometimes this pocket can move around depending on rpm and the movement of the car.

Joe

 

Is there a procedure somewhere for bleeding? It is quite possible there could be air in system. The heater core was disconnected for about a year (was sealed though) and though I did power flush everything before hooking the valve etc... up, I am sure there was air in the heater core.

 

The fact that you are getting proper heat at idle probably indicates that the system is working correctly and the core does not have a problem -- some early ones did --- not sure if it was a core material or the early coolant issue.


If the coolant tank is filled when it is cold -- then it is filled. Jaguar does have an extra procedure -- start the car cold and fill the tank up -- install the cap before the engine warms up. When you start the car cold you will see that the level in the tank will drop before it gets hot. By doing this you are really over filling the system -- the extra will eventually go into the fender overflow. This is why sometimes the warning light will come on just after you start the car and then go off. This procedure in is a TSB - they tell you to only do it once.


I wonder if you have the wrong thermostat installed or it is not working correctly? I'm not an expert on the Jaguar system -- so I can't say for sure how much the thermostat is involved. Modern cars have a cooling system that is vastly oversized for many markets -- so in winter weather you need the thermostat to regulate and restrict the coolant. Otherwise the engine will cool -- this effects emissions and fuel usage. Looking over the system i don't see any other part that would do this. I never install aftermarket thermostats - important little things.

 

It's the season for heater woes.
Does the heater matrix return hose connect to either the upper or lower RH inlet of the heater control valve?
The schematic sort of indicates the upper but sucking and blowing experiments seem to indicate the lower and hence a straight path to the heater pump.
I have the return hose connected to the upper inlet but the heat is very weak.
The matrix has been flushed and the control valve and pump work.

Thanks again,

Dan

 

Check out my post "heater problems". I had a similar issue that turn out to be a clogged heater core. I used straight CLR for 20 minutes, then pulsed with pressure from a garden hose. CLR can eat through a heater core in bad shape, but worked great in mine.

 

I took the liberty to look up CLR and what precautions you need to take and this is what I came up with.

CLR Frequently Asked Questions and listed under FAQ I found this.

"Can I use CLR to clean out my radiator?
No, CLR should not be used on a car radiator for two reasons. First, CLR may not be compatible with the internal metals of the radiator. Second, it could have adverse effects if the CLR is not rinsed out completely."

Although I admire your creativity and desire to find a fix I would recommend that your procedure not be recommended as a fix just yet. Improper use and flushing of the system may cause a catastrophic effect resulting in additional problems. I would recommend calling or writing CLR and see if they can elaborate on your application and the mix with antifreeze.

 

True, CLR clearly states on the bottle, not to be used on aluminum and other metals.

That being said, I have used it on my XJ8 and two other customer cars as well with no leaks so far. 1 year on one, 6 months on another, and only a couple of weeks on the XJ8.

The import part that didn't elaborate on is that each application needed a heater core replacement from being clogged anyway so worst case I was replacing the core.

In each application, I disconnected the heater core to only run CLR through the core and not the rest of the cooling system. And I'm fairly certain there was no CLR left in the core when finished.

I found out about this technique from a VW tech who uses CLR all the time on Passats that come in with clogged cores.

This has worked for me and others when all other flushes have failed.

 

In my case, when the engine is at idle the heat is pretty strong.... cruising down the road the heat gets weak.

So it would seem my heater core isn't clogged....but I am wondering if the little aux pump shuts off at higher engine RPM's and perhaps that would have something to do with me not getting much/any heat at cruise....