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1995-2002 Range Rover P38A
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Discussion Starter #1
I am ready to pull the tubes out the heater matrix and replace the O rings.

I suspect-- based upon the access holes- that someone has already replaced them. But I do not know how long ago or if recently. In either case- I now have a slow leak so I am wondering if belt and suspenders is the approach I should take. O ring plus Silicone.

Normally I only apply "O ring grease" on O rings before I install them- it has been my assumption that O rings are made to move so you put some sort of lubricant on them--and you do not apply any additional sealant which could immobilize them.


I read the Forum sticky on O ring install and I noted that a few forum members said to use a new O ring and to also apply silicone to the joints-- then let it set up before you water test.



How many here on the Forum have found that they needed to use silicone in addition to new O rings? If so- do you use it around the O rings or apply it after the O ring?

Thank you for your opinion.
 

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1995-2002 Range Rover P38A
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If you’ve got a leak then I suspect you’ve pinched one of the Orings, or the pipe isn’t aligned,a bit of grease wouldn’t hurt, if you can, get someone to put the screw in while you keep the pipes aligned in the slots
 

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1995-2002 Range Rover P38A
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Discussion Starter #3
Thanks, Chris

--so you are in the camp who say that if the O rings are installed correctly, and the tubes inserted/aligned correctly-- you do not need silicone.
 

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You shouldn't need it but it isn't likely to do any harm. I always get the pipes in position, do the screw up lightly then give the pipes a wiggle to make sure they are fully seated before tightening the screw fully.
 

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1995-2002 Range Rover P38A
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Discussion Starter #5
Thanks Richard-- because it looks like someone has already replaced the O rings due to the access holes drilled, I was worried that getting the O rings compressed correctly was a bit finicky- thus the question of using silicone sealant as a backup.

Also- some recommend removing the hoses from the pipes - and other do not mention doing this. I attempted to remove the hoses using a bent awl to get between the hose and the pipe to relieve the sticktion but could not get up far enough in each pipe. So I cannot pull off the hoses gently. I think I will leave the hoses on.

Had almost two feet of snow that last few days so have been digging out- will release the pipes today and see how far I can pull them back to remove and replace the O rings.

This is my first Range Rover so of course, I bought a p38 which has many of the classic issues so well covered in this forum.
 

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1995-2002 Range Rover Classic
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never use any additional sealant on "O" rings, it defeats the purpose of their ability to seal, you can however use lubricant to make them slide and mate better.
 

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1995-2002 Range Rover P38A
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Discussion Starter #7
thanks--- I always just lubricated O rings- but a few "been there done that" write up said to always use silicone in addition to the O ring if you wish to prevent further leaks.

I do not discard hard-earned knowledge when I have no past history on any new machine I buy and need to wrench on. So I ask.
 

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1995-2002 Range Rover P38A
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I replaced mine this summer and did not use Silicone. When I did a leak check with tap water I had a major leak. I did not line up the pipes correctly and did not push them in all the way. Correcting that resulted in a good seal. I used Viton O rings as recommended in the forum. Got them from McMaster&Carr. Don't recall the size but it is in a forum post, just search. Used a socket head machine screw instead of Philips. Had to drill out my original screw as no way would it turn. Used a 12 inch drill bit. All day job.
Good luck.
 

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1995-2002 Range Rover P38A
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Viton o rings only don't use the black ones 22mm diameter 2.5 mm thick use silicon grease to aid fitment . if the screw is not removable drill the head of the screw and remove the pipes . undo the screw backwards as it has rusted from the back , this is why it will not move, use a mirror to see inside the housing that the surface is clean, that's very clean no scale also the pipes must be clean . on install do not over tighten as this will crack the plastic housing on the core, tighten and back off about half a turn as it will expand when hot . that's my 2 cents worth.
 

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Discussion Starter #10
Viton o rings only don't use the black ones.
Mad--- I just received 10 black Viton O rings of the correct size per the write-up from McMaster Carr.


Why not use the Black ones---are they not as good as another grade/color Viton?

I use green O rings for gasoline but thought all colors were fine for antifreeze.

My O rings were stiff and hard-- so someone must have replaced them a long time ago if at all. Perhaps they installed a Matrix-which would be nice and may explain some of the strangely positioned cutouts.


-----Gordon-- also going socket head but I bought 20 mm and the one I took out was 25 mm. So this has come at the right time for me to reorder.
 

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Viton Orings are better quality, more resistant to chemicals, UV light, just a better all round ring compared to nitrile orings, if you want to change the screw for an Allen key type or similar,I believe it’s 5mm, it’s another design fault in all honesty, if you work on the engine and move the pipes there’s a chance that the hardened orings will crack, pretty much a standard change when i do head gaskets these days just to cover myself. It does sound like you misaligned them, they are a 3 handed job till you get the hang of them..
 

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1995-2002 Range Rover P38A
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The heater design in P38 is really bad. Sooner or later it will leak, and if neglected it will kill your BeCM. Mine has been replaced at least once. Audi heater core is the permanent fix, everything else is a band-aid.
 

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1995-2002 Range Rover P38A
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Discussion Starter #13
Chris-- I already have a set of black Viton O rings of the correct size. I misunderstood MAD until I looked closer at what he wrote. I thought he said not to use the "Black" viton O rings-- I have seen white and green ones so I assumed a better grade viton. Now I see he meant not to use the OEM Black BUNA O rings.

So I have the rings ----now to find a longer 5 mm capscrew
 

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Discussion Starter #14
jt- after having owned and wrenched on many older Audi's- I am unaccustomed to hearing that an Audi part is a robust replacement option.
 

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1995-2002 Range Rover P38A
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jt- after having owned and wrenched on many older Audi's- I am unaccustomed to hearing that an Audi part is a robust replacement option.
I agree that as a general rule Audi parts are rarely a robust replacement option. In this particular case, the Audi heater core is a much more "conventional" design that has no O-rings, eliminating this failure point. If you buy a quality heater core made by Behr, it will last longer than the rest of the P38.
 

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1995-2002 Range Rover P38A
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Genuine or Audi ? There’s another thread, lol, I personally don’t like the way the rubber pipes are run with the Audi core, will my p38 matrix blow up ! , having owner 14 range rovers, 12 of them being p38s and never had one fail yet, I doubt it, it’s the old question of maintenance, anti freeze being a must, has it ever been cooked, all factors
 

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Discussion Starter #17
Chris--- always seems to be two sides when it comes to replacing OEM parts.

I understand you are pointing out that overheating (cooked) would stress the stock matrix, but I am unclear of what type of maintenance will prevent matrix failure. Are you saying that changing out the antifreeze on a regular basis will keep the matrix healthy? Or are you pointing out that you must use a recommended antifreeze due to the aluminum heads and prevent the matrix and the radiator getting plugged up?


In a nutshell-if you have had an overheating episode high enough to blow the head gaskets --you should assume that your matrix was overstressed and should think replacement at the same time as head gasket change out? I am 50/50 sure I need to do the head gaskets- but not sure they failed from normal wear (saw a video where the mechanic said you can assume head gaskets after 50K miles on a 4 or 4.6 motor) - or overheating by a prior owner.



By the way--what is the antifreeze you recommend?

Thanks again Chris---
 

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1995-2002 Range Rover P38A
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I use oats antifreeze in mine, I think most p38s have had a head job, or will at some point, saying that, I know of one with 200k and still running on existing from new, head gaskets at 50k is possible, but I would thing a higher mileage than that, as I said, maintenance is a must, I’ve done many head gaskets that have failed no where near the water ways,and many that have, just looking like they have deteriorated.
owning a p38 is a love of your car, once you get all the niggles out the way there’s no reason why it shouldn’t be like any other car, I’ve had 2 years with 1 minor fault ( lambda sensor ) but when I bought my latest one it was week to week work, your get to know the car inside out, and of course there’s always this site when your stuck.
 

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1995-2002 Range Rover P38A
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Discussion Starter #19
Hi Chris-

I am probably the "last Tag" owner of this P38. Bought it from a guy who has a number of LR's but does not work on them himself. He had it only for a short time before I heard about it. He was happy to pass it on and now that I have it in my garage I know why.

But for some reason a beat up Holland and Holland should be restored rather than parted-- at least this is what I feel at the beginning of this journey.
 

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1995-2002 Range Rover P38A
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Viton o rings are for chemical use (brown in colour) anti freeze is a chemical , its also corrosive and it attacks the back of the screw , that's why it goes rusty if you do anything with this screw replace it with a stainless steel one.
 
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