The service manual has to this say about any cooling system flushing:

"CAUTION: The heater core must be back flushed separately from the engine cooling system to prevent the engine cooling system particles from clogging the heater core tubes and reducing (or eliminating) coolant flow through the heater core. All engine cooling system flushing and back flushing procedures must include a separate back flushing of the heater core after the flushing or back flushing of the engine cooling system.

I understand that to say that any flushing/back flushing of the cars cooling system must be followed by a back flushing of the heater core. My question is twofold.

Wouldn't back flushing the heater core just send whatever grunge is in it all through the system unless you take the heater core parts out of the loop and back flush it by itself.?

Second question. Has anyone taken the core system out of the loop and just back flushed it through it's inlet and outlet piping, and if so where did you do the disconnect? Up where it makes the switch from rubber tubing to metal piping or somewhere else?

Since my heat function has gone away this winter and everything else is operating as it should I suspect that the core is plugged. I've done the MAX heat setting to see what happens and there's no change and the external temperature reading is correct with no more than a degree or two differential so I must assume that the temp sensors are operating as they should.

That snake pit of a cooling system slithering around, under, and through the block itself would be a bitch even without the tight fit so even if I needed to flush the cooling system, which I don't since it runs fine, I'd need a major type of feel good medicine or several stiff drinks to undertake such a task.

Anyone done it recently without needing a lift and an advanced engineering degree?

 

It's been awhile since I owned my XJ but yes you can flush just the heater core and you can access the hoses near the front of the engine. IIRC I did drain some coolant to enable decoupling the heater hoses from the front and not spill. I just can't remember where exactly but it's easy enough to follow the heater hoses out from the firewall.

Back flushing is easy enough but remember the heater core has pressure limits so if you use a garden hose, no need to put in on full blast.

All that said, I have yet to read anyone who successfully back flushed a heater core once it was clogged. The silicates are just too hard to remove. Heater core replacement is usually the option. Good luck though and hope it works out.

See post 2 for more detail
https://www.jaguarforums.com/forum/x...e-hoses-51087/

 

Might be best to eliminate a tired aux pump before getting into backflushing?

 

Agreed. My input assumes troubleshooting was already completed.

 

Since I need to check the level sensor in the expansion tank and get a look under there anyway for both a small leak and a constant low coolant warning even though is isn't I'll get a chance to check the aux coolant pump as well, but I'll do a back flush of the heater in any case as the car is now 15 years old and as 120,000+ miles on it and probably never had a radiator flush ether. Probably this coming weekend if the weather cooperates.