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[Boatboy]

Thinking my rad to be blocked I have today removed it and given it a good flush out. Sure enough I got seven shades of proverbial out of it, including some quite lumpy bits of scale.

Can somebody please educate about the purpose and operation of the auxiliary coolant pump and pipework. The reason I ask is that as soon as the engine gets warm this pipe gets warm, and to my way of thinking it is providing an easier route for the coolant rather than going through all those narrow channels. Consequently this can get untouchably hot whilst the matrix itself is still cold, even up to the point when the fans kick in.

If I wrap this pipe in rag and pinch off the flow, it does seem to have the effect of  forcing more water through the rad.

Any explanation would be welcome. BTW, not that I think its related but the aircon is U/S.


Steve

[TheBoy]

If your rad is staying cool, its shafted, and replacement is the solution if you can't clear it.

Aux pump allows for hot coolant to circulate to provide cabin heat after engine switched off, if reqd.

[Boatboy]

Thanks for that. Never seen that system on a car before.

Do you know if there should be some kind of shut off valve for when the engine is running, or is it just set up as a permanent parralel circuit which carries more or less flow depending on the cleanliness of the rad?

Steve

[TheBoy]

no valves needed - if the rad is ok, its free flowing enough

Also, remember the pump has resistance in form of impellors

[Boatboy]

Cheers for that. And bugger.

Time for some online radiator sourcing.

steve

[TheBoy]

Cheers for that. And bugger.

Time for some online radiator sourcing.

steve

might be worth trying the breakers on this site...

[Andy B]

...............

Aux pump allows for hot coolant to circulate to provide cabin heat after engine switched off, if reqd.

Which pump? There's only the one next to the top of the rad on my 99 pre facelift. And I believe just dissipates heat around the system when you stop the engine when it's hot.
Just face lift cars that have the ability to give a flow through the heater  when the engine's stopped.

[Boatboy]

Thats the one, fitted to the side of the rad tucked up near the battery.

I do not have a handbook, so don't know if my 99 gls has that feature. Sure don't know how to turn it on if it has.


Steve

[Elite Pete]

I always take my rad out, remove all the rubber hoses and leave it overnight lying flat with Fernox in it. That really cleans the crap out

[Andy B]

Thats the one, fitted to the side of the rad tucked up near the battery.

I do not have a handbook, so don't know if my 99 gls has that feature. Sure don't know how to turn it on if it has.


Steve

face lift onwards only!      

[Boatboy]

It maybe face lift only for the cabin heating operation, but the pump and pipework are all there on my old banger.

Just come in from some experiments. If I clamp off the pipe the rad heats through as it should ie no cold spots etc, and cools when the fans cut in.

Remove the clamp and pipe gets hot, rad matrix cools, when fans cut in they run for longer.

Turn off when fans are running and aux. pump springs into life until fans stop.

My conclusions are that the aux system on this vintage is as mentioned earlier designed to circulate water whilst engine is cooling, and either the flow resistance of the radiator is too high or the resistance in the pump is below spec.

Either way the rads coming out again tomorrow, maybe for some of the Fernox treatment.


Steve

Just a thought. I am assuming my plumbing is correct in that this auxilliary takes water from the hot side, via its pump, across the top of the fan and into the cold side.

sb

[Andy B]

........ but the pump and pipework are all there on my old banger.

 ........

That's what I meant. But some 'old bangers' also have another pump under the header tank/brake master cylinder area ....... because i don't have one, i've never really bothered to find out which have & why ...... & have forgotten when told!