P38 heater o-rings: draining tips?

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
Getting closer to changing the o-rings, subject to Royal Mail ever condescending to drop a new pair of the little blighters through my letter-box.
To give the fixing screw little or no chance of declining to release the pipes from the matrix, I have ordered a 12” 1/4 hex extension and will use a Wera PH3 bit, as the screw (pictured) seems to be Philips, not Pozi. Is that correct?

IMG_F81985029F90-1.jpeg
 
P38 Monkey said:
Getting closer to changing the o-rings, subject to Royal Mail ever condescending to drop a new pair of the little blighters through my letter-box.
To give the fixing screw little or no chance of declining to release the pipes from the matrix, I have ordered a 12” 1/4 hex extension and will use a Wera PH3 bit, as the screw (pictured) seems to be Philips, not Pozi. Is that correct?

View attachment 331251
Click to expand...
Can't remember if it's Philips or POZI but I threw it away and replaced with a SS Allen head screw to make removal easier next time.
 
They protrude out the back, that bit goes rusty and then it can bind up just as you think you are winning.
Get something on that before you start. My new genuine O rings started leaking again sometime, can't remember how long, after I did the job. Got fed up and ordered the audi matrix, started the job and when I got to that screw...it wasn't particularly tight! Tightened it up some more and it hasn't leaked since. I think the hot and cold coolent cycle slackened things a bit or I'm a bit limp wristed.
Audi matrix still in its box.
 
P38 Monkey said:
Getting closer to changing the o-rings, subject to Royal Mail ever condescending to drop a new pair of the little blighters through my letter-box.
To give the fixing screw little or no chance of declining to release the pipes from the matrix, I have ordered a 12” 1/4 hex extension and will use a Wera PH3 bit, as the screw (pictured) seems to be Philips, not Pozi. Is that correct?

View attachment 331251
Click to expand...
That screw head is a pozidrive,
phillips does not have the little bits between the cross.
 
IMG_3791.jpeg
IMG_3790.jpeg
IMG_3792.jpeg
IMG_3793.jpeg
IMG_3795.jpeg
IMG_3796.jpeg
Job done..
Set up with polythene sheet, absorbent mat, fluid guide (cut-away plastic bottle), washing-up bowl, safety bund consisting of a suitably pink bath towel.
Following the tips and guidelines, I used an “I’m not asking” screwdriver with PZ2 bit, very carefully lined up and applied super-smooth pressure.
To find that the screw was not even hand-tight… D’Oh!
But that wasn’t the cause of the leak - see photo - both o-rings very hard, brittle and cracked.
Having syphoned coolant out of the overflow tank, about 1/2 litre, when I pulled the tubes off the matrix, nothing came out of the top one, and only a very small dribble out of the lower one.
Re-assembled with copper grease on the stainless Allen screw, Lucas red grease on the o-rings.
Checked for leaks and refilled the system - all looking good.
I have left the trim off for the moment, with an absorbent pad tucked in place to show any drips and leaks.
I’ll check the bolt for tightness in a while.
Thanks again for the tips and advice..greatly appreciated.
 
Quick update - interesting (well, sort of…) - after a run about the place, I checked the fixing bolt and found it was not tight. Not leaking, but definitely needing tightening. As it is an M5 into aluminium, I am tightening to 2.2 Nm. Bearing in mind comment above, glad I left the panels off and checked….
 
P38 Monkey said:
Quick update - interesting (well, sort of…) - after a run about the place, I checked the fixing bolt and found it was not tight. Not leaking, but definitely needing tightening. As it is an M5 into aluminium, I am tightening to 2.2 Nm. Bearing in mind comment above, glad I left the panels off and checked….
Click to expand...
I used Loctite on mine thinking the heating cooling cycles may loosen the screw. As it's a socket head, it should come out OK if the need arises.
 
Datatek said:
I used Loctite on mine thinking the heating cooling cycles may loosen the screw. As it's a socket head, it should come out OK if the need arises.
Click to expand...
hmmm - I went the other way, with copper grease. Might remove the bolt carefully and use medium strength loctite. As with many things on a P38, it’s like defusing a bomb. With no pressure in the system, what could possibly go wrong…
 
P38 Monkey said:
hmmm - I went the other way, with copper grease. Might remove the bolt carefully and use medium strength loctite. As with many things on a P38, it’s like defusing a bomb. With no pressure in the system, what could possibly go wrong…
Click to expand...
Even with no pressure in the system, plenty will leak out and the joints will be wet.
 
Last edited:
Datatek said:
Even with no water in the system, plenty will leak out and the joints will be wet.
Click to expand...
Yes, of course - thanks. I’ll check tightness a few times and when/if stable, will put the panels back on. I am leaving a puppy-pad in there with the lower edge just protruding so can see if any leaks restart, as well as soaking up anything that escapes.
 
Follow-up comments:
After one cold-hot-cold cycle, the fixing bolt was definitely a bit looser, although the joints were not leaking. I tightened it up and it has stayed tight, so I fixed the panels back in place.
I left the pad in place as a tell-tale, and will pull it out after I am confident that the o-rings are sealing well.
Once again, many thanks for all the advice.

I don’t have this kind of problem with my 1965 Triumph Spartan - it doesn’t have anything as namby-pamby as a heater…

IMG_3826.jpeg
IMG_0716.png
 
Oh dear, the coolant leak has returned. I took off all the panels etc - the allen bolt is still tight and there is no leaking coolant on and under that o-ring joint. The leakage seems to be under the matrix itself - looks like a new matrix required.
Maybe a previous airlock has just cleared itself, which would explain why, when changing the o-rings, almost no coolant came out.
Reading various comments, an Audi replacement seems best, but some people prefer Nissens - any opinions gratefully received.
People also have had problems with aftermarket Audi heater rads - and I have had good results with Nissens products in the past.
Seems that the Nissens 70220 will fit - looks like it’s an Audi equivalent anyway…


Thanks, as ever.
 
Last edited:
That's what I have in one of mine. Originally did it because the LR matrix had broken plastic flange & the aluminium pipe ends were also bent by the PO.
 
P38 Monkey said:
Oh dear, the coolant leak has returned. I took off all the panels etc - the allen bolt is still tight and there is no leaking coolant on and under that o-ring joint. The leakage seems to be under the matrix itself - looks like a new matrix required.
Maybe a previous airlock has just cleared itself, which would explain why, when changing the o-rings, almost no coolant came out.
Reading various comments, an Audi replacement seems best, but some people prefer Nissens - any opinions gratefully received.
People also have had problems with aftermarket Audi heater rads - and I have had good results with Nissens products in the past.
Seems that the Nissens 70220 will fit - looks like it’s an Audi equivalent anyway…


Thanks, as ever.
Click to expand...
This is the one I fitted a few years back

NISSENS 70220 HEAT EXCHANGER​

Cost £20 4 years ago
 
You will also need a pair of reducers to go between the matrix hoses & the engine hoses. Can't remember the size, but there's threads on here with the correct size. Nissens 70220 has 17mm fittings. I think the engine bay needs 19mm ?
 
Last edited:
You can buy a nissens matrix that has the 19mm outlets for a better job but more expensive.
I got one with the 19mm because I thought my seals had gone again but it was just a loose bolt.
Mines still on the shelf in the workshop. In two minds as to sell it or not but I can get the part number off the box for you at least if you want.
 
Flossie said:
You can buy a nissens matrix that has the 19mm outlets for a better job but more expensive.
I got one with the 19mm because I thought my seals had gone again but it was just a loose bolt.
Mines still on the shelf in the workshop. In two minds as to sell it or not but I can get the part number off the box for you at least if you want.
Click to expand...
Let me double-check the leak and if the matrix is leaking I’ll buy it off you… thanks! UV dye is on order to do some leak detection…
 
You must log in or register to reply here.

Similar threads

A
P38A Heater matrix o-ring / pipes - advice needed !
2
Replies
24
Views
3K
P38 Monkey
P38 Monkey
awkwardbob
P38A Air-Con ‘O’ Rings Condenser and Dryer
Replies
2
Views
536
tomcat59alan
T
C
P38 Diesel Heater Matrix Bypass
Replies
16
Views
2K
Rubberknees
Rubberknees
C
2001 P38 Diesel heater core bypass
Replies
17
Views
2K
Rubberknees
Rubberknees
5
Scared it into healing itself?
Replies
1
Views
630
Hippo
Hippo
Back
Top