2001 Galaxy TDI Ghia - cooling system / heaters issues

[aquilaalba]

Hi all, newbie here, I've just got my first diesel Galaxy, it had a bit of history behind it - it blew the hose going to rear heater, lost coolant, but didn't cook, as per garage advice the head gasket was replaced, did happen again now, but... I've flushed the system, filled it (I think, it's weird to fill - at least it seems to me) took much less than I'd expect, but took few hoses off and all seems filled with coolant. Now for the pipes going to the back heater - one is hot, the other stone cold. It's got the gizmo controlled electronic unit, so no knobs to manually select temperature, etc. With the hoses off I've checked flow through rear heater matrix and it flows freely in both directions (hose pipe down both pipes), flow must be present, as one pipe gets hot, HI is selected on both front and back of the car on the module, front starts blowing warm air (didn't run it too long to prevent blowout), but pipes on the back stay one hot one cold. There is flow on return pipe to the bottle, squeezed all accessible hoses - help? Any ideas? It drove 30 miles with temperature bang on 90 degrees, but with closed cap it will blow off the pipe under the car. No water in oil / oil in water.

[johnnyroper]

Is the run on pump working?
Could be air locks in system they can be temperamental to bleed.

But as you say with cap on it blows a hose off that sounds like head/gasket issue causing excessive pressure to me.

[johnnyroper]

Just another thought the cold pipe have you tried disconnecting both ends and trying to put hose on to make sure it is free of blockage down itââ,¬â,,¢s entire length?

You could also try bypassing under bonnet so coolant does not flow to rear heater and see if system still builds up excessive pressure.

[aquilaalba]

As for run on pump I can hear something running, presumably it's the said pump. As for head gasket, I've read that if the bolts used are not from 130BHP model, they might stretch in time and need re-tightening 90 degrees.
Now, for the pipes, I've flushed the pipes running under the car both ways - through the rear matrix and up towards the engine, both of them, either way I've had water coming back through the other one. Flushed the rad, yet on filling the system it seemed that it didn't took enough, around 4 litres? Given, it wasn't completely drained, as the thermostat was left in place. Belt, pump, thermostat were replaced together with the head. Head wasn't confirmed to be faulty, block was checked, old head still with the car, seems fully useable, with no faults - passed the pressure testing, etc. It seems a bugger to bleed, had similar problem with SDI previously, but due to my impatient mate who insisted on keeping the system under pressure (not leaving the cap open to start with) we ended up frying the bugger. I was thinking if I could bypass the heater on the back and connect both pipes under the car. How can I disconnect the rear matrix system and revert to basic PD engine to eliminate potential issues? Thanks for all replies.

[brianh]

The run on pump keeps going after the engine is switched off for a few minutes, so if you can hear a faint humming then it should be ok (its on the bulkhead just behind the expansion bottle if you want to check it further).

To bypass the rear you'd be best to loop the two feeds somewhere up the front end near the run on pump.

I'd have a check that the front matrix is getting a decent flow through it - you should be able to disconnect pipes from both sides on the bulkhead and flush it through from there, I'd suspect if thats blocked that you might struggle to get much flow through the rear heater.

A Full fill should be around 9.5 litres of coolant, it takes a lot as it has to fill the pipework to the rear.

[aquilaalba]

Right, bit of an update. This bugger is not heating up quickly, got the flow, as return pipe is fetching fluid back, did top it up few times, had it driving about with temp up to 90 degrees and over, yet the pipe on the lower front stays cold, no matter what. Thermostat was supposedly replaced, but just bought a new one and will fit it tomorrow, as no faith in the current one. Will drain the system, flush the block this time too and fill it really slow, bit at a time, with the car front lifted a touch. Heating works well front and back, back was non existent, also after good flush both pipes are warm, so no longer an issue there, but might have been blocked. One of the joining pipes at the bottom / rear was kinked, if it'd get hot it'd restrict the flow, cut it shorter now and should be good. Will report back tomorrow. Temperature stays around 90 though, heating works, so not sure 100% but seems ok so far, apart from thermostat not opening.

[johnnyroper]

It will take a lot to get thermostat to open in a PD engine especially in this weather. The engine produces very little wasted heat that needs dissipating to the cooling system. To get thermostat to open you need to put engine under some load like towing,long up hill runs etc.
So long as heaters work ok and temp gauge holds steady at 90 I wouldnââ,¬â,,¢t worry about it.

[brianh]

For it to blow the hose off under the car seems strange - given you found it kinked it might be the pressure from the run on pump causing it to come off as nowhere else the pressure could go, maybe down to a dodgy hose clip or similar. All you can really do is try and drive it now and see what happens, but given the rear heater is now getting hot does suggest you've located and sorted the issue there, hopefully thats all it was.

[aquilaalba]

What made me think I need to change the thermostat was that yesterday I managed to get the temperature to 97 degrees tops (OBD2 plug in bluetooth unit / phone readouts) and left top rad pipe was still cold, yet the fan kicked in, so thought that it would be expected that full flow should be on, before the fan would get  activated? Correct me if I'm wrong, as was working on assumptions here... Might keep it this way and drive it first. Need an MOT now anyway.

[brianh]

I don't own one of the diesel Galaxy models, and never have, but the usual way the fan is triggered is off a seperate switch or sensor, either in one of the radiator pipes, or the radiator itself. As theres little point cooling the already cool/cold radiator. As soon as the stat opens it will drop the temperature of whats going in significently by mixing with the much cooler coolant on the radiator side. So the fan not kicking in doesn't indicate much. Though the fan will usually be on at the slower speed if the aircon is switched on anyway.

Don't know what the pipework arrangements are for the radiator offhand, they would usually fill from the top though, it does sound like the thermostat should be opening at that temp to me, though if it isn't managing to get past 97 degrees I wouldn't be too alarmed as long as you don't seem to end up with excess pressure problems again.

I think your best to drive it and monitor it personally from what you see happening.

[johnnyroper]

Unless the air con is on the fan should not be triggered if thermostat is closed as rad fan switch in screwed in to rad on offside. (My auy was so assume all the same)

[brianh]

Unless the air con is on the fan should not be triggered if thermostat is closed as rad fan switch in screwed in to rad on offside. (My auy was so assume all the same)

Most of those switches will only trigger when the switch is at around 90 degrees, and switch off when it drops to 80, so it shouldn't be on unless the radiator is fairly hot if thats where the switch is. The petrols have them in the top hose so would probabbly trigger sooner.

[aquilaalba]

Hi all, had the system all flushed again this time with thermostat removed, so could flush the block as well, replaced thermostat with a new one, replaced expansion tank cap with the old one (has been replaced, yet replacement had holes blocked with some sort of head-gasket-wonder-repair stuff - coppery colour), bled it and it runs perfect, heating works great front and back, thermostat starts to open over 80, as pipes do start to feel warmer and around 90 degrees it's hot on both rad pipes - all seems good, system isn't pressurizing so fingers crossed. Drive it a bit to test, then MOT and off we go! Found booster heater underneath too, will look into that at some point, but that's another topic. Thanks for all your help.