[1.9D DW8 Dispatch] My blowers don't get very warm following an oil cooler leak. Heater matrix clogged?

[kenbw2]

A great many miles ago I had a leaky oil cooler. Long since fixed, three coolant flushes and a thermostat later that seems to be behind me.

Except for my blowers, they're just not very warm at all.

Engine temperatures fine - 85 degrees most of the time, 90+ at idle before the fan kicks in.

Interestingly they're... acceptable... while driving, but as soon as I stop to idle, they go stone cold.

My theory is that the tight holes in the heater matrix (it's like a radiator, right?) might be clogged with oil, and isn't letting coolant through very easily. When driving the pressure will be higher so it's exchanging some heat, but at idle the the pressure isn't enough.

Before I delve into it, does my theory have legs?

[white exec]

I've had oil in coolant, and it was difficult to completely clean out.
Finally used this:
Liqui Moly Radiator Cleaner (ref 2506) 300ml
Contains anti-calk and solvents specifically for removing oil and grease from the system.
Sufficient for up to a 10-litre system, so you may need a second can.
Full instructions on the can.
Excellent stuff; works really well, and left everything spotless.

[Bick]

I would take the advice given above ^^^^^ but also make sure the cooling system is bled correctly.

[kenbw2]

I've had oil in coolant, and it was difficult to completely clean out.
Finally used this:
Liqui Moly Radiator Cleaner (ref 2506) 300ml
Contains anti-calk and solvents specifically for removing oil and grease from the system.
Sufficient for up to a 10-litre system, so you may need a second can.
Full instructions on the can.
Excellent stuff; works really well, and left everything spotless.

Oh I wasn't thinking of cleaning it, but replacing the heater matrix entirely. From what I can see it's a bit more accessible in the Dispatch(/Synergie) than it is in other cars so for £30 screw it.

Just wanted to check that what I'm saying makes sense before I do replace it.

[white exec]

Ok, so it sounds like a possible matrix blockage.
Try detaching the heater supply/return hoses in the engine bay, and mains-water pressure flushing the matrix, in both directions.
If it flows freely (wasn't blocked), then likely cause could be a stubborn air-lock. These can be obstinate to shift, and some engine layouts require a temporary "header bottle" on the reservoir, plus copious use of bleed screws with a hot engine, to get rid of them.
Airlocks also have the odd property of "coming and going", which could explain why heater is sometimes hot, sometimes, not . . . . ie intermittent flow.
If you just replace the matrix, and bleed the system properly, then any airlock might simultaneously disappear anyway!!

[kenbw2]

Ok, so it sounds like a possible matrix blockage.
Try detaching the heater supply/return hoses in the engine bay, and mains-water pressure flushing the matrix, in both directions.
If it flows freely (wasn't blocked), then likely cause could be a stubborn air-lock. These can be obstinate to shift, and some engine layouts require a temporary "header bottle" on the reservoir, plus copious use of bleed screws with a hot engine, to get rid of them.
Airlocks also have the odd property of "coming and going", which could explain why heater is sometimes hot, sometimes, not . . . . ie intermittent flow.
If you just replace the matrix, and bleed the system properly, then any airlock might simultaneously disappear anyway!!

Hadn't considered the possibility of an airlock. That said, my coolant system has an elevated header tank so I don't think I have the need for the bottle trick.



It doesn't particularly come and go at random, it's definitely consistent with high revs vs idle. I can sit still with high revs and feel it warming up, although I accept that still doesn't rule out the airlock possibility.

If I'm taking it all apart and draining the system etc I'll replace the matrix anyway for the sake of £30. But I'll still try your suggestion of putting mains water pressure through it and see what happens as it'll help me know if it was the matrix at fault or something else.

Edit: I just re-read your comment and noticed you're saying do this in the engine bay, not on the heater matrix in/outlet. Maybe I can try that first (if those pipes are easily accessible).

For when I put it all back together, do you think I need to worry about bleed screws etc with my high-up expansion tank? Or can I just fill up from the top of the radiator till that fills, then put the rest in the header tank?

[white exec]

Hi Ken,

That header tank is in a decent position, Ken (shame they didn't do them all like that!).

For a thorough bleed, on XM - where header tank is above engine, but not as high - mandatory procedure is thus:

- Fit bottle (piece of old radiator hose is firm fit into the expansion tank neck, and blocks drain hole) and half fill with coolant.
- Bring engine up to normal working temperature (may take a while when idling!), and maintain bottle half full.
- Open bleed screws in turn [on XM, there is also one on the heater matrix supply pipes next to bulkhead].
- Squeeze one of the large hoses vigorously to encourage air out.
- Continue until cooling fans have cut in, preferably twice.
- Keep header bottle at least half full throughout.
- Leave engine to cool, with header bottle in place.

A 1-litre bottle is sufficient. If it vibrates unacceptably (because expansion tank is engine-mounted), hang a heavy weight from the bottle top rim.

Could be a bit OTT for yours, but it is thorough.

[kenbw2]

Thanks for that. I knew there were various tricks including the bottle one (my Peugeot 106 had the same situation as your XM) to encourage air out, good to have an end-to-end list of tasks. I hear rumour from the Berlingo DW8s that they have bleed screws near the heater matrix supply pipes too, near the bulkhead. I assume the same is true of mine.

I'll give that all a go (without the bottle) with just plain water first and see if it helps my blowers. If they come back to life I'll put some antifreeze in and leave it at that. If not then I'll start diagnosing the heater matrix, with a view to replacement.

By the way, for a 23 year old car, that's a clean looking engine bay.