Been having heater problems on my 2008 L322 Vogue. Air cond working but no heat. Looking at the forums I found:- Heater control valves (replaced them, no difference), Airlock (bleed the system 5 or 6 time no difference), FBH pump and secondary pump (remover and tested, no difference) now time to think for myself. Fired up the FBH from cold and felt the 3 pipes going to the heat control valves and found the bottom pipe gets very hot (FBH to valves) then the two upper pipes (valves to heater) started to get hot but very slowly, then the FBH started to kettle and shut the FBH down on overheat. So pumps working, heater control valves working, FBH working and no circulation, after looking at the heating diagram in the manual the only thing left in the circuit was the changeover valve which decides weather the coolant for the heater comes from the engine or the heater return. I thought if it was stuck it would still allow coolant from one of the inlets, WRONG! I removed the cabin air plenum (the pollen filter housing) (remove the rubber seal from the rear of the engine bay, remove two nuts, one either side of the plenum, and pull the whole plenum forward and out) and you will find the changeover valve bolted to the bulkhead on the right as you look at it from the front of the vehicle. Remove the three hoses from the valve and unplug the wires, remove the two nuts from the valve bracket and remove from the vehicle. Remove the valve from the bracket, remove the 4 screws around the top of the valve and pull it apart, clean and lube with silicone grease and put back together, put the vehicle back together, fill coolant, bleed and hey presto, heater works, FBH works.
I hope this helps someone.

Excellent piece of information. Could you feel the actual valves getting warm on the valve block, but not allowing the coolant to pass by into the heater matrix.

Did you take any pictures & what sort of grease did you use?

The valves are connected to the bulkhead via 3 aluminium pipes, the bottom one is the flow from the FBH so carrying the hot coolant to the valves, the top two are carrying the hot coolant to the matrix. On mine if I felt the bottom pipe and it was getting very hot but slowly, then the heat started going through the top 2 pipes but slowly again, therefore the 2 control valves were open but the system was blocked somewhere else, and the only other point was the changeover valve. When I removed the changeover valve I tried blowing through it and all 3 ports were blocked. I use Regin silicone grease as I used to be a heating engineer and it sits on the shelf but any lube that won't attack rubber will do the trick. Good luck.

Hey Ian,

Hows the fix going? I have just come to the same conclusion on our 2007 TDV8, exactly the same symptoms in that the bottom pipe is scorching hot but nothing on the top and the FBH shuts down. Interestingly sometimes it does operate and the top pipe also get warm.. The FBH Pump was replaced last year and the aux water pump runs. Quick search let me to your post which sounds identical!

Our heat is fine when the engine is running, and the FBH also runs with the engine so I suspect ours is in its "normally open" position.

Thanks,

Tom

If your heater works with the engine running that rules out the temperature control valves and looks like the changeover valve as it is used to changeover from FBH to engine coolant. A right sod to get too but mine was easy to fix with just a clean and lube. Good luck, hope it goes well for you.

Just be careful when removing the valve and bracket from the bulkhead as they have used nylon nuts and they round off very easily. Best to use a 6 side socket. The valve isn't an open close valve it's a 3 port valve, out to the temperature control valves which splits it to two and feed the heater matrixes, in from the FBH and in from the engine coolant. When the engine starts the FBH starts and feed the heater, when the engine reaches a said temperature the FBH shuts down and the changeover valve switches to the hot engine coolant. My valve had stuck in the middle and nothing was flowing.

I’ve had it out tonight, wasn’t too bad I decided to clamp off the FBH and matrix return pipes and then take it out with the third still attached which I kept high to avoid dropping too much coolant.

The mechanical side felt fine, but it could have been my initial push that freed it off a little. I haven’t tested it as I was a little scared to apply 12v as I wasn’t unsure of the polarity and I’ve lent a friend my multimeter.

The FBH fired once it was back together and ran, but as above it did occasionally so could be a fluke.

Will try it in the morning from stone cold and see what happens, it’s certainly something like this.

Thanks for the heads up - I’ll report back.

Please note that the rubber seals in the changeover valve can swell enough to block flow regardless of valve position. 2007 L322 3.6 TDV8 Stornoway

Last edited by S.Hafsmo on 18th Dec 2018 7:46am. Edited 1 time in total

Ian,

Just a thought, did you separate the solenoid and grease inside as well? Or just separated the solenoid from the valve/main body? Just wondering how far they can be stripped down.

Thanks,

Tom

S.Hafsmo wrote:

Please note that the rubber seals in the changeover valve can swell enough to block flow regardless of valve position.

Good point, on mine the flow was perfect from both sources when operated by hand

FBH ran fine this morning... fingers crossed.

Help! I have put the problem down to the control valve but cannot remove! Is ther a way of in doing the 4 screws on top and doing it in situ?

HJi. Is Ian Daniels still on here?
Just need some help with the Valve please

Just trying to bring my Posts up to 3 so I can message!

Ian Daniels last posted in 2018 so I doubt he is on here any more...

I think you will have to decide for yourself if you can take it apart in situ... personally I doubt it, get a garage to do it if you are unable to...  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Thanks Pete. I can get to it in situ and remove the 4 screws on the top but cannot it apart as more than likely seized and would like to know what it contains! i.e. if iI do get the top to lift out, will I be able to clean and grease and then slide it back together? I cannot find anyone selling a second hand one on the internet so I could have a go on the bench before trying to force it