P38 Diesel Heater Matrix Bypass

Hello group, been redirected to this section of the forum. In the process of renovating Blenheim Place - also known as a 2001 P38 Diesel (RHD), which has had many parts of the cooling system modified. My plan was to re-instate the viscous fan and cowling (successful so far - car sounds right - I know having a viscous fan is a hotly contested debate on the forum, I try to stick to the original design as far as I can where possible), I also replaced the expansion tank cap as coolant was leaking out of the overflow on the tank. When doing a test of the system, I found to my dismay that I now have a cabin dripping with coolant on the drivers side of the cabin. Looks like the O-rings or the heater matrix could not cope with the pressure change when I replaced the coolant cap. At some point I will have to go through the world of hurt to replace the o-rings/matrix/ maybe Audi matrix conversion (still ruminating on the best approach on that - it seems to be a nightmare no matter which option is adopted).

My question is as follows.
Planning a temporary bypass to the heater matrix to allow me to confirm that the rest of the cooling system is good. I assume I can use a U-shaped pipe to link the supply and return together. Can anyone advise what pipe size/material would be suitable to work as a temporary bodge until I can muster enthusiasm to replace the broken matrix?

Being a plumber i would and have done on other motors used copper tube and soldered fittings,
if i remember right the pipes through the bulkhead are 18mm so 15mm yorkshire end feed elbows and push the rubber pipes over the end of the fittings.

Matrix is a whole weekend dash out job.

If you remove the panel under the steering column I think you should be able to see the joint where the pipes come through the bulkhead. If it is leaking you might be able to get someone to wriggle them from the engine side until they seat properly. Might get you out of jail.

Grrrrrr said:

Matrix is a whole weekend dash out job.

If you remove the panel under the steering column I think you should be able to see the joint where the pipes come through the bulkhead. If it is leaking you might be able to get someone to wriggle them from the engine side until they seat properly. Might get you out of jail.

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Looks like its leaking without any pressure in the system at all, Which may mean the matrix has gone as well - Fun times! This is why we buy these vehicles and run them though. Not for the glory, not for profit, but for fun!

clarkie1973 said:

Looks like its leaking without any pressure in the system at all, Which may mean the matrix has gone as well - Fun times! This is why we buy these vehicles and run them though. Not for the glory, not for profit, but for fun!

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After a lot of welded on hose pipes (and boiling water hurled on then to loosen them off, heater matrix has been bypassed, and now testing the rest of the system. No leaks so far, coolant temperature in the lower third of the black section, viscous fan drawing air as needed. Now to convince myself of the merits of a dashboard remove to replace dodgy heater matrix, vs simply fitting a PTC heater in winter......unless some one has already come up with a PTC conversion option?

You can fit a Audi one once you get old matrix out they don’t have o rings that leak

LR adopted the method of cutting a hole in the side of the dash behind the panel to change only the O-rings. Still nasty job getting your arm in there working blind but you’ll see some with a hole cut there.
No good if you’re changing the matrix and better job have it all out anyhow.

Google PaulP38.comheater core replacement. Could be a lot easier than full dash out

Taking the dash out isn't as bad as it sounds. Plus, all the joints in the ducting will be leaking by now. I think that might help drive moisture away behind the dash but if you disagree you can use the opportunity to reseal the lot with draught excluder and make sure all the air makes it into the cabin / windscreen.

RangeRoller dt said:

LR adopted the method of cutting a hole in the side of the dash behind the panel to change only the O-rings. Still nasty job getting your arm in there working blind but you’ll see some with a hole cut there.
No good if you’re changing the matrix and better job have it all out anyhow.

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It looks like the panel is pristine (so I'm thinking maybe original heater matrix), I'll look to remove the dash board as per PaulP38 instructions. The HEVAC needs to be pulled out to put in the screen fix from RPi Engineering in any case, must order a tonne of bags to label each stage of this disassembly.

As a side question, (still undecided about Audi vs pattern part), if I went the Land Rover aftermarket route, in the forum's opinion, what is the best/reliable aftermarket matrix to buy? or is it worth sucking it up and getting an original Landrover part?

Audi version is an upgrade and cheaper as far as I am aware.
Wouldn’t worry too much about bagging things up - all the bits are different and fairly self explanatory. I put them together where they came from stacked in the boot. Nothing can blow/roll away and you know which bit to refit next as it it comes out the reverse you put it in.

Audi one is slightly bigger and requires a little light filing to fit. @MrGorsky fitted one to his. Think @martyuk has done a few too.

I've done plenty of the Audi heater core swaps. There is a rib in the middle of the heater box which needs to be removed (a sharp chisel will do it) as the Audi core is just a little bit fatter than the LR one.

martyuk said:

I've done plenty of the Audi heater core swaps. There is a rib in the middle of the heater box which needs to be removed (a sharp chisel will do it) as the Audi core is just a little bit fatter than the LR one.

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Is this an early morning post or an evening one Marty? You back in the UK?

tomcat59alan said:

Is this an early morning post or an evening one Marty? You back in the UK?

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No, he's not back till April at the earliest.

Grrrrrr said:

No, he's not back till April at the earliest.

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Just seen his post in 4.6HSE.

Can anyone tell me which Audi core it is. I've read about it but not sure which one to buy. Please