Front Heater Hassle

[jackasti]

Greetings Bongophiles,
Front heater problem: Cylinder head replaced following a spectacular failure 2 months ago. Pre failure engine running at 85 Deg C. Now running at 74 Deg C.
No heat coming from front heater. Working well before cylinder head blew.. Both hoses to heater are cool after a run. Fan working fine. Thermostat not changed when the cylinder head was done as it was replaced 4 years ago when a new radiator was fitted.
Cylinder head replaced by Bongo expert and system drained and filled properly.
I have been informed that the heater matrix is a free flow thing:
Any thoughts or solutions? Do you know if heater matrix's clog up?
I am thinking air lock in Matrix: Knackered thermostat: blocked heater matrix.
Any and all advise, especially in any diagnostic techniques, would be most appreciated.
Thanks
Colin: North Norfolk

[Bob]

Does sound like an air lock or blocked matrix.

I'm guessing the heater control was set to hot when the engine was bled?

[francophile1947]

Thermostats can easily be ruined when overheating - have you actually checked that it's working?
It sounds as if it could be jammed open, hence low running temperature.

[jackasti]

Hi, I am pretty sure that the chap who carried out the work would have set the heater controls to hot.
He says that he has replaced a few heater matrix's but only due to leaks and has not yet come across a blocked unit.
I think we will try and drain and refill the coolant as a first step and give the matrix a flush.
Is there a definitive diagnosis technique to check a heater matrix for blockage or airlock?

[rita]

You need to check that the thermostat is working as it should.

Good Luck.

[mikeonb4c]

Hi, I am pretty sure that the chap who carried out the work would have set the heater controls to hot.
He says that he has replaced a few heater matrix's but only due to leaks and has not yet come across a blocked unit.
I think we will try and drain and refill the coolant as a first step and give the matrix a flush.
Is there a definitive diagnosis technique to check a heater matrix for blockage or airlock?

I've come across Adrian my mechanic (and Bongo expert at Japandirect) changing a heater matrix because it was clogged. It definitely can happen and if there were indications when the head was replaced that rubber coolant pipes were crunchy with scale deposit then I think its quite possible the heater matrix might also be clogged (maybe with the problem compounded by scale dislodged during the head replacement).

P.S. and I agree with Rita about checking the thermostat

[Allans]

Heater matrix can and do block. I've seen several partially blocked causing poor flow of coolant.
74* is too cool.
If he has an infrared thermometer gun, get him to check the temperature variations in the system.
Suggestions - Change the thermostat and re bleed.
If that doesn't fix it, reverse flush the matrix until it's free flowing and clean. If it doesn't free flow, replace the matrix.
Refill and bleed.

[jackasti]

Thanks, All for the guidance and advice.
Off to the Bongo man tomorrow for a discusion.
Looks like a summary of advice = Drain, check/change thermostat, check/change matrix, refill, drive......Take off gloves and thermals and bask in the warmth of a hot Bongo.

[Bob]

Since the 'stat has to come out to check it I'd just replace it then check to see if it was working.

[Northern Bongolow]

agree with all the above.
get a cheap meat thermometer or a laser temp jobby, they are both cheap. under the bonet find the 2 pipes that attach to the heater matrix about 25mm dia, they are under the heater fan unit and against the bulkhead. measure the temp of these when its warmed up, then measure the temp of the bottom hose that runs from the rad bottom back to the stat housing, the heater circuit should be a lot hotter, both in and out, than the bottom hose. if they are similar then the stat is probably stuck open or non existent.

i would only fit a gen mazda stat not a copy, these are proved to be less reliable.

[windywatson]

If its been back to mechanic,What was the cause?

[New Forest Terrier]

Did he replace the matrix? There are faulty ones around. I had mine replaced at Discount Trucks after a split and there was no heat from the heater afterwards. Found out driving to Gatwick at goddam awful cold hour and assumed head was about to go from airlock. Returned Bongo and the new matrix fitted was faulty. Fred changed the matrix and all was well.

I was really worried as I wanted to see how the expert bled a Bongo and mine was just driven around the block both times and pronounced done. Its a V6 and apparently he's bled it four times that way without any trouble. It bleeds easily apparently. Totally bemused but its still going fine after new radiator and heater matrix x 2. Lives up to its BewilderBeast name.

[jackasti]

Thanks for replies and advice.
Hopefully off to the Bongo expert tomorrow. Chap was busy replacing 3 x cylinder heads from Bongos and his own truck is having heater problems. I have passed on all advice but I remain convinced that the problem is the thermostat.....find out next week
Fortunately the weather in Norfolk is at 10-12 degrees C...

[jackasti]

Just back from the Bongo Master. Thermostat function checked and all OK. Heater matrix flushed through half a dozen times..both ways. Plenty of crud and corrosion in the flush. Now back to normal heat so either an air-lock in the matrix or blocked waterways. Bottom radiator hose changed at the same time as it was bulging.
Looks like a new heater matrix at some point but if this one can keep the screen clear and my hands warm it will remain a task "For Another Day"...

[Bob]

Well done.