2001 P38 Diesel heater core bypass

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clarkie1973

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Hello group, and first post on this forum. Hopefully I will not commit any cultural Faux Pas (Facebook and I no longer speak anymore). 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?
 
clarkie1973 said:
Hello group, and first post on this forum. Hopefully I will not commit any cultural Faux Pas (Facebook and I no longer speak anymore). 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?
Click to expand...
Welcome to LZ!:)

Try the Range Rover section with that one.

https://www.landyzone.co.uk/forum/range-rover.10/
 
Correct place ;)

Not sure where you get your information, general concensus on the forum is to keep the viscous fan for the sake of incremental cooling. There are some members take different school of thought and go electric conversion.
Both work.

Audi matrix upgrade is fine, may only be o-rings but while you are all the way in there...

Shouldn’t really piddle out of the cap - hope you don’t have combustion pressure in your coolant system. Anyway,
Welcome to LandyZone :)
 
The original expansion cap was leaky after 15 minutes on idle from cold. Radiator hoses were still pliable and not rock solid. Temp gauge was in normal range the whole time. That got replaced (just in case) with the OEM part. After that was installed, the heater matrix o rings started leaking about 10 minutes after startup from cold. Unsure when they were last replaced, so on the repair list. I figured I should bypass the heater matrix in the mean time and confirm no more fluid loss.
 
clarkie1973 said:
Hello group, and first post on this forum. Hopefully I will not commit any cultural Faux Pas (Facebook and I no longer speak anymore). 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?
Click to expand...

More likely you've disturbed the o-rings moving the cooler pipes around. Matrix has been known to leak. If so an Audi one can be made to fit with rubber hoses so no more o-rings.

Is it coolant leaking? There are also sunroof drains, drains for the aircon and pollen filters / screen surround leaks that xan drop water in the cabin.
 
It does seem to be coolant dripping (orange tinged) and it seems to originate from the area where the heater matrix lives. Air conditioning compressor doesn’t have a belt connected to it at the moment. I suspect this hasn’t worked for a few years - this got me thinking that the fans at the front of the radiator might never spin up to cool the system, which prompted the fitting of the viscous fan. Agree that the upheaval of tinkering has probably upset the o-rings.
 
clarkie1973 said:
I’ll check that this morning. Thanks for the tip.
Click to expand...
Had a quick look this morning, and it looks in reasonable nick, no evidence of wet in that area, so hopefully one less thing in the worry pot.
 

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What I'm thinking here, with visual aid.
2 = return from heater matrix
3 = supply to heater matrix

remove hose end at 1
connect hose end 2 to end 1

Would that work as a bodge or am I missing something (also possible)
 

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