Thread: Heater O-ring replacement in progress.

Clean the pipes thoroughly. Dip the O-rings in straight coolant, e.g., glycol, to lubricate them before fitting.

Don't overtighten the screw on reassembly as it may cause the heater core to crack and thus leak. I used a stainless steel allen head cap screw.

Thanks Ron, your contributions to the Range Rovers.net forum have been a huge help to me tackling this job for the first time.
I was tempted to cut the ducting, but I thought better of that and followed your method of flexing it out of the way.
Do you recommend pulling the pipes right out to clean them, or leave them where they are?
Thanks, Pete.

Rons thorough explanations about p38s are absolutely brilliant

His corrections on the England language on the other hand.....

Originally Posted by PeterH

Do you recommend pulling the pipes right out to clean them, or leave them where they are?

They are damn difficult to clean in situ. Mine had a solids encrustation around the raised section on the pipe where it was not visible and it leaked after I put it all back together.

I'd never thought of pulling them out. I see no reason why you shouldn't. If you do that, do one pipe at a time and mark them "top" or "bottom" as appropriate. I knew of a P38A where a chap had got them reversed and could not get a seal because the pipes just didn't seat properly as the angles were wrong.

Whether overtightening causes the crack in the heater core is not known. Suffice to say that both jsp (on this forum) and I both had the heater core crack in exactly the same place. John (jsp) sent me his heater core to compare with mine.

Should sealant be used? I don't know. I used glycol to lube the O-rings and they don't leak. One thing I try to avoid is moving the other end of the pipes under the bonnet as I don't wish to disturb the O-ring seal.

I ended up having to do mine the long way (dash out) as the screw head on the clamp plate was stuffed


Upon the advice of folks on this forum, I also replaced the screw with an Allen head cap screw.


I don't think I did a write up of it, but I did take lots of photos and uploaded them to
Heater O-Rings

Might be something in there that is of some use.

Cheers, Paul.

Those photos are excellent Paul, thanks for sharing, I can see how the clamp slides back now, the very thing I'm just about to do!
Very helpful, I'll be able to refer to those while I do mine.
I'll let you know how it goes!

Originally Posted by PaulP38a

I ended up having to do mine the long way (dash out) as the screw head on the clamp plate was stuffed


Upon the advice of folks on this forum, I also replaced the screw with an Allen head cap screw.


I don't think I did a write up of it, but I did take lots of photos and uploaded them to
Heater O-Rings

Might be something in there that is of some use.

Cheers, Paul.

Is that stripped screw head accessible to a hand held reversible drill? With this and a left hand helix drill bit the stripped screw will simply wind out. No need to remove the dash.

Have an update for you, I was doing a few jobs at once, new radiator, new hose (off the bottom of the thermostat), new coolant temp sensor on the heater pipe, as well as the o rings. I got it all back together and started her up. Wouldn't you know it, coolant still leaking from the o rings!
Not happy Jan.
Thought I may have been a bit too careful doing up the heater clamp screw, so I very carefully did it up a bit tighter. Started her up, hey presto, leak gone! Very happy with myself right now.
The pipes were actually pretty clean, but I did give them a once over to be sure.
Was tricky getting the o rings back on, then getting it all back together, half the battle is getting yourself in the right position so you can see what's going on.
All seems well now, thanks once again for your help Ron and Paul.
Now to reassemble the drivers side, then tackle the blend motor on the passenger side.