How to test the coolant pump?

Nedavno Pete M napisa:

Yes.

Nedavno Duncan Wood napisa:

Could be. I have another one, and when I find some time, and weather improves, I'll change it and check if that helps.

BTW evaporator was connected parallel to the heater, on the same line as waxstat (coolant heated cold running idle regulator - hope I got this right :-)

That way heater worked only when engine warmed up to the running temperature. And when it was very cold idle rpm went up if while I was stationary.

So now I connected it in-line with inlet manifold heater, in place of hose part #19 here:

Hot coolant goes in the evaporator from the point where hose clamp part #20 is and goes back to the coolant system at the inlet manifold at the other end of the hose #19.

This way I got my heating and cold running idle back.

To explain further hose #9 goes in the radiator, hose #8 out of it. Hose #15 returns coolant from the manifold, and hose #17 from the waxstat. There are also another hose from the heater to the inlet manifold, and another one from the engine block to the waxstat - that are not shown here.

I doubt the evaporators faulty, there just might not be enough heat available. If you can find a carburetted VW polo in a scrappy then they've got a handy heater element in the inlet you could cannibalise.

Nedavno Duncan Wood napisa:

And do what with it?

fit it to the inlet manifold, it's designed to cope with petrol, but it should work with lpg.

Nedavno Duncan Wood napisa:

LPG needs cold air, cold inlet manifold. Only evaporator need heating. I should fix low coolant flow (if I have one).

Nedavno Conor napisa:

So if i take the pump out, and impeller is good, I can also check that it is not detached by hand (holding the pulley, and trying to turn the impeller)? How is the impeller fixed to the shaft?

Bolt it to the evaporator then.

Normally they're just a tight press fit. Anyway I'll predict there's nothing wrong with your water pump. Faults like that are as rare as hen's teeth. I just think your evaporator is either not well designed and is not heating up enough or the way it's plumbed in means there's not enough flow through it because the water is finding other routes round the engine.

Nedavno Duncan Wood napisa:

I don't think that is the right thing to do. I have another evaporator, I'll fit that one, and see if gets any better.

Nedavno Dave Baker napisa:

When it froze I touched both in and out evaporator hoses, and both were warm. Do you think that if coolant flow is low that out hose should be cold?

Err yes, if they're both warm then the evaporators not extracting any heat. Presumably you've tried flushing it? ( Presumably there is actually some flow?)

Nedavno Duncan Wood napisa:

No I didn't. I only fitted it recently, and I think that it is OK. I have another one, and I'll put that one in, and see what happens.

There must be, when the engine warms up almost to the running temperature, evaporator temperature goes up. When I fit my spare evaporator I'll check if there is something blocking coolant (but in that case out hose should be sufficiently colder than in hose).

Of course if there's lots of flow then in & out will be almost the same temperature, what temperature is your coolant?

Nedavno Duncan Wood napisa:

Wen the engine warms up, the needle in temp gauge is where it's always been (OE thermostat says 80C, so I guess around 80 degrees Celsius). But evaporator freezes at lower temperatures.

Try a real thermometer & possibly change the thermostat, Dave probably knows better than me but I'd have thought you could happily run a good 8 deg hotter than that in winter safely.

Nedavno Duncan Wood napisa:

It's been like that for 20 years now, and it's BMW thermostat so I do not think I'll change that.

But I just thought of something. "In" hose for evaporator heating goes form the point ~15 cm (~6") above the evaporator and the return hose goes up and than down to about the same level where "in" hose starts. Like this:

Could it be that I have some air in the evaporator? How do I get it out without spilling half of the coolant all over me and garage?

There shouldn't be, it would rise to the out hose.

Nedavno Duncan Wood napisa:

So why do you have to bleed air out of the some coolant systems if coolant would go out trough the out hoses?