308 1.6 Petrol, no heat!!!

[Matt1969]

Bit of a strange one this, no heat in cabin.
First, back flushed heater matrix, then rad, then coolant system.
Refilled, bled system from heater hose at bulkhead and thermostat. Still no heat, took to garage as they suggested thermostat maybe at fault. They replaced thermostat and housing, and replaced water exhaust bypass hose that was split.
Refilled and bled system told me all done. They also said had to dig out copious amounts of rad weld from water pump.
Drove car today 15 miles, came upto 90c, still no heat. Top rad hose very hot, bottom hose very cold. Cabin temp cold.
Fan, heater controls all work OK, but no heat. Have I missed something? Or do I back flush whole system again? Any help would be gratefully received as heater matrix replacement cost very prohibitive.

[white exec]

Hot rad top hose and cooler bottom hose sounds normal, but how about the two hoses/pipes going to the heater matrix?
You should be able to feel the temp of those in the engine compartment, where they head off through the bulkhead.

You say there is no heat in the cabin, but is the heater matrix itself getting hot? It should heat up at the same rate, and to the same temp, as the engine block. Hot engine should mean hot matrix. Just wondering whether the matrix could be blocked or airlocked, or, if ok, whether the problem is blower air circulation through it.

[Matt1969]

Thanks Chris,
Inlet to heater matrix hose hot, outlet cold. Bottom rad hose isn't just cooler, but stone cold. When flushed through, did reverse flush first on both rad and matrix, then inlet flush.
Refilled with coolant and bled thermostat and bulkhead bleed valve. Bottom of rad warms up then, but not matrix.
When thermostat,housing replaced by garage they found copious amounts of rad weld which they took out. I'm just wondering if any of that is still in the system? Heater blower works fine, air con works fine, and cools down as it should.
I think I will try another reverse flush and cross my fingers before thinking of heater matrix replacement.

[white exec]

Sounds as if the heater matrix is completely blocked, probably as a result of the radweld.
Normally, temps of hoses connecting to the matrix are pretty much equal, if the flow through it is good.
Heater matrixes are very fine tube sizes, so can clog first.
If replacing it, Nissens brand have a very good reputation.

[Matt1969]

Thanks very much for the reply. Heater matrix change first then as rest of system is flushed. I'll get on and order one now, as all other usual suspects have been sorted.
The garage bill for the matrix is over £450, so will be doing this myself.
Thank you for the advice.