Thread: Heater O-ring replacement in progress.

It just slips on, no need for any specific sealant. If anything just coat the new seals with some coolant before you fit them. I did mine almost 2 years ago and was amazed how straight forward the process was. Also be carefully not to over tighten the centre bolt on the o ring bracket as its a fairly weak metal compound and easy to strip. Another tip when completed is the importance of not mixing coolant type, just pick a brand and stick to it as the net effect can be a chemical reaction which can eat into the seals.

Sometimes the new O rings take a little time to seal

Interesting finding poleonpom, have you had seals take a day or two to seat in?
I had a closer look today, the seals do appear to be doing their job, I'm scared to say it looks like there is a leak from the heater core in the area where the pipes join, possibly as Ron B described.

horrible design.

if your going to the effort of dash out i would replace the heater core with a unit from another car with fittings for rubber hose to be clamped on. The design in my classic which is the same as the disco is a bit better with a clamp on each pipe, but is still a poor design.

I have done my O-rings at least half a dozen times now, and have replaced the core twice.

Last time I did them I put a little bit of red RTV sealant inside the bores for the pipes/orings (very small amount) and clamped down the pipes. Hasn't leaked in the 6-7 thousand k's since but may just be luck.

This is where my first core leaked from and cracked - where the bolt head seated:



Took me a while to work it out and was thanks to Ron actually, he saved me ALLOT of time.

Also the thread stripped on the ally plate behind the pipes on mine, so in the end I filed down a bolt to fit between the pipes and put a longer bolt through the whole arrangement.

I found the heater core connections to be the weakest point in my car when I was having overheating issues, as they seemed to leak and fail under pressure than any other part of the system.

Also be careful as I bent my pipes unknowingly at one stage and I think that might also have led to sealing issues, and I replaced them once also.



Two years ago I drove home Canberra to Adelaide with the heater core bypassed as the o rings went on the morning I was comming home and boy was that a cold trip home, on the other hand I had a major failure where both pipes came out under pressure and my feet nearly got burnt and it took a week to dry the car out.

Thanks for those photos jsp, I'm fairly certain that is the exact point mine is leaking too.
I got under there today with a mirror and torch, the heater pipe clamp is still bone dry, the o rings are doing their job, the leak is definitely coming from the same point you have arrowed.
Oh well, at least I know what it is now!
I'll be ordering a new heater core tomorrow.
Will have to put up with the leak for the week though, next weekend will be my first chance to do the heater core replacement.

Originally Posted by PeterH

Interesting finding poleonpom, have you had seals take a day or two to seat in?
I had a closer look today, the seals do appear to be doing their job, I'm scared to say it looks like there is a leak from the heater core in the area where the pipes join, possibly as Ron B described.

When I first changed the seals I was really careful about cleaning the seating area etc. i took it slowly and thoroughly and when I tightened the connection and re-charged the water I couldn't believe the amount of water coming out. I have a really long phillips screwdriver and I carefully increased the torque in the connection, but with no result. Only after 3 attempts did the leek result in a drip - I'd had enough and thought I'd leave it until I could source some better O rings, and then after 2 days not a drop of coolant

I had a similar experience, I was a bit too tentative at first, with coolant running out of the connection after the first tighten, I increased the tension a bit more and it stopped on the second go. My new heater core has arrived, will be picking that up tomorrow and fot that on the weekend, fingers crossed that sorts the problem out!