SEARCH

You are in: > Home > A1 Catalogue > DIY Helpline

306 Heater

Hi Bill,

Here is the problem.

1995 306 1.9TD.  The heater blows cold air for about 6 minutes of normal driving from cold.  The temperature gauge seems to be reading normal.  Then you get a blast of warm air from the heater but not really hot.  This lasts for a bout three minutes then it goes stone cold again.

When the car came home from a 20 mile journey last night the heater was blowing cold air out and the rad fan was on (not usually).  What would cause this cold/hot/cold/hot effect?

I have a 94 405 with the same engine and that warms up after about a mile.

My wife is fed up with getting cold so its time to seek help.

I topped up rad today as the expansion tank was a little low but it seems to have made no difference.  Left it ticking over for ten minutes and its still blowing cold.

Heater controls (manual not elec) sound to be opening and closing OK.  No visible water leaks and no smell of rad water inside or excessive condensation.  Any ideas??  Blocked matrix maybe or thermostat??

Thank you
Mark Allen


Hi Mark,

My guess is more or less what you suggested - either a faulty heater matrix or a faulty thermostat but it could also be a faulty heater control valve.

This is usually fitted under the bonnet on the bulk head on the heater unit (though I'm not certain exactly where it is on your model).

A visit to your favourite garage should be able to confirm which of these it is.

If you've got a breakers yard near you, try them...Many of them sell these things and offer competitive fitting service as well...worth a try?

Let me know how you get on.

Regards and good luck.
Bill


As far as I am aware there is no heater control valve.  Just pipes straight through the bulkhead.  The manual doesn't mention or show one and I can't see one.  If my understanding of the system is correct then hot water should be circulating round the block and heater until the stat opens.

That poses the question as to why the heater only gets warm after SEVERAL miles and then goes cold again.  If it (matrix) were blocked surely it would stay blocked hot or cold.  I am baffled by it.

I may try disconnecting the hoses and flushing the matrix through with a hose.  Then re-connect and see what happens.

Mark


Hi Mark,

Have you tried feeling the heater hoses where they enter and leave the heater?  If it's hot one side and not the other - it could well mean a blockage or an air lock.

If it were the thermostat I would expect the temperature gauge to read low?

It may well be worth putting a cooling system flush through the whole system, you may be suffering from radiator collapse (sometimes the alloy inside the rad starts to crumble and falls to the bottom - this prevents proper circulation - though it usually causes overheating - this might explain the cooling fans coming on and slight water loss.

Flushing the whole system should help.

Worth a try.

Regards
Bill


Thanks for that Bill. I will look in to it in the daylight.  One heater hose (bulkhead) was hot the other cold.  Still pointing to a blockage.  But WHY does it clear, let a bit through then block again?

I will persevere and let you know what I find.

Reluctant to put any harsh cleaners in the system because I have read today that the 306 matrix is prone to leaking.  I don't want the chemical burning through a matrix element if it gets stuck in a tube.

Also read that the matrix tubes run up and down instead of side to side.  This lets sludge and contamination stick in the u bends at the bottom of each.  Keeps Peugeot in the spares business no doubt.

Replacing the matrix sounds like a nightmare.  I am not taking the dash off a car of that age.  Not worth the agro.

Mark


Hi Mark,

I'm pretty sure that this matrix is one made of an alloy mixture - this corrodes and collapses and causes the blockage...some water will seep through and that's probably why it gets warm sometimes etc.

It sounds very much like it is the matrix, should you decide to flush the system it's advisable to flush any flushing agent out thoroughly at least a couple of times with clear water which should clear any debris that gets into the system.

I hope I've been of some help...good luck.

Regards
Bill


Hi Bill,

Turned out to be a massive air lock.

I went to disconnect the rubber hoses from the heater hoses in the bulkhead.  I was expecting to loose coolant so was ready with grips for the pipes.  When they came away there was no spillage at all.  I carried on and flushed the matrix through thoroughly from both directions and only got a small amount of solid residue out.  Re-connected everything and checked the rad cap.  Water level was normal.  I made a header tank for the rad out of an old bottle, opened the bleed screws and got a litre of antifreeze in and a litre of water until all the air was out.

Went for a spin.  Phew it's hot in here.  End of problem.

Not sure where the air got in or the water got out.  No white smoke in exhaust, no bubbles in rad water so no head gasket problems.  No wet carpet or steamy winders so no matrix leak.  No visible leakage anywhere.

It seems you can be fooled on this model because if the coolant level is OK it doesn't mean that the system is full.  It's uphill to the heater pipes and thermostat housing so there are lots of places air can get trapped.

Thanks for the advice.
Mark


Hi Mark,

What a guy...Well done, it really takes determination to achieve what you have - you can be justifiably proud.

It's difficult to know exactly why some air locks appear - please keep your eye on the coolant level for a few days - just in case!

Your success will be an inspiration to others who view my free website.

Again well done and thanks for letting me know how things worked out.

Regards
Bill


No Problem, great site.  Used it a few times now over the years.  Sometimes it's nice to run my theories and suspicions about motor problems passed someone a lot more qualified.  If you go to a garage they are usually very tight with info because they obviously want the business of putting it right and certainly don't want the likes of me fixing problems.

Job took me about an hour.  Most of that was trying to free rubber hoses in a confined space.  The hose clips are the sprung type and boy are they tight (fingers hurt as a result).  Can't beat good old jubilee clips if you ask me.  Easy to use/replace and cheap too.  Most clips on a Peugeot are tamper-proof now and require cutting off.  Makes a simple job damn difficult.

Thanks again.  No doubt I will be in touch again for more advice.  Keep up the good work.

Mark


Well done and thanks Mark
Bill