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[PaulSW]

Hi all,

I'm having coolant issues with my not-so-trusty MV6 and I'm at that throw some money at it/trade it in for something different crossroads. Advice would be welcome, and if there're any SW mechanics here who could come and do some work for a few quid it would be appreciated.

Had the car just over 12months. The coolant warning on the LED display came on once or twice (months apart), I checked the level in the dump tank, it was up to the "cold" line, thought no more of it. Then in December it came on two or three times over a couple of days, initially I ignored it but when I did get round to checking it, there was nothing in the tank. Oh dear, I said to myself, bought a litre of premix thinking that should do it, poured it all in with still nothing in the tank. Got some more and eventually got it up to the level, drove it a few times, the level didn't seem to budge although the warning did still come on once or twice.

But it's happened a couple of times since, seems okay for a while then just suddenly starts boiling coolant, resulting in a nasty gurgling noise from the pipework and a fair bit of coolant back in to bring the levels back up.

The battery died late last year and everything on the car seemed to instantly work better when I put a new one in, but within a few days it started seeming a bit tired and grumpy again - I say this because I wonder if both issues are belt-related, resulting in poor alternator and water-pump performance? I thought if the water wasn't being pumped around properly, it would just boil what was in the block and then force it out along with whatever fluid it meets along the way. There is sometimes noticeable steam coming from the drivers side of the bonnet.

I know nothing about engines, so if I knew what the fault was I could figure out how much it would cost and decide whether to fix or get rid, but as I don't know the source I'm warey of spending a couple of hundred quid on it just to find it's not worth fixing. I would like to sort it out if I could as I generally like the car, but I'm not really willing to spend more than £2-250 on it as it's just not worth it in the long run.

Thanks in advance,


Paul

[dbug]

Check the HBV (heater bypass valve) for leaks - its behind engine towards drivers side - when leaking you should see coolant dripping off bottom of bellhousing. If HBV feels damp/shows visual signs of leakage - replace it.  Howto in Maintenance Area
HTH

Vx replacement part about £35 from memory,  1/2 hour to fit

[Kevin Wood]

When does it overheat? In traffic or at other times?

Does the system pressurise when hot? Check if you can easily squash a radiator hose when hot. They should get firm. If not, the expansion tank cap may be your issue.

If in traffic, check the cooling fans run with the air con on, or as the coolant temperature reaches a little over the mid point on the gauge.

If not, I'd say the radiator is sludged up, the thermostat is defective or possibly the water pump impeller has disintegrated.

[Entwood]

If you are losing that much water by "boiling" as you call it through the pump not working .. the engine would be behaving like a kettle and whistling at you !!! 

IMHO you must have a leak somewhere, the question is where ...

HBV mentioned above can be intermittent and only leak at certain cabin heating demands .. try runing the engine at idle until fully warmd up and then changing the temp required from hot to cold and back ... watch the HBV area for leaks

Header tank neck can develop small cracks, or the cap can fail and not hold pressure, both can be checked by listening for small "hisses" when the engine is fully at temperature, or brushing a soapy solution around there

Other leaks may be found by adding some strong yellow food colouring to the coolant, so that the water colour changes dramatically, then running the engine and looking for the yellow traces.

The fact you see steam is worrying, and also a confirmation you have a leak .. you need to find and fix that leak ..

[allen25]

Paul,

Coolant fluid loss is something I've experienced and I suspect many of us have too. From my own experience over time, it is often fixed easily and at not too much cost. Diagnosis wise, where is the leak dripping from underneath the engine? If parked on unlevel ground, it might be more difficult to trace the source? Hopefully you will find it dripping somewhere?

[dbug]

Boiling could be due to low very low coolant level resultant on the loss of coolant by leakage.  Intermittent loss does point to HBV.

[PaulSW]

Thanks for all the input 

The steam due to low coolant levels after loss elsewhere suggestion sounds likely. it seems to vent from the drivers side of the bonnet a couple of inches from the windscreen.

On Thursday the coolant was really low, nothing in the tank. I bought 5ltrs of pre-mix and put around 2-2.5 in to bring it up to the level, then started the car and ran it for 5-10mins with the cap off to see if anything happened; it didn't. I drove to work, about 4mls/20mins in stop/start traffic. Checked the level before I left work, hadn't budged, drove home another 3-4mls in stop/start traffic. Same drive the following morning, I can't remember when I checked the coolant again but it was later that day, and it had gone down 1-2cms from the cold fill level. I had also checked the oil cap at some point and found a good old dollop of mayo, although I did read somewhere that this can happen under normal conditions with a lot of stop-start driving.

Could this drop in level just be due to air in the system working its' way around? If I top it back up and keep an eye on it, maybe it will level out.

I've also found over the last few weeks that the 'ECO' button has stopped functioning, I don't know if this might be related.


Paul

[dbug]

Thanks for all the input 

The steam due to low coolant levels after loss elsewhere suggestion sounds likely. it seems to vent from the drivers side of the bonnet a couple of inches from the windscreen.

On Thursday the coolant was really low, nothing in the tank. I bought 5ltrs of pre-mix and put around 2-2.5 in to bring it up to the level, then started the car and ran it for 5-10mins with the cap off to see if anything happened; it didn't. I drove to work, about 4mls/20mins in stop/start traffic. Checked the level before I left work, hadn't budged, drove home another 3-4mls in stop/start traffic. Same drive the following morning, I can't remember when I checked the coolant again but it was later that day, and it had gone down 1-2cms from the cold fill level. I had also checked the oil cap at some point and found a good old dollop of mayo, although I did read somewhere that this can happen under normal conditions with a lot of stop-start driving.

Could this drop in level just be due to air in the system working its' way around? If I top it back up and keep an eye on it, maybe it will level out.

I've also found over the last few weeks that the 'ECO' button has stopped functioning, I don't know if this might be related.


Paul

Thats where the HBV is sited mate

Doubt its air in system mate if you are seeing steam - you've got an intermittent leak, which will get worse

[PaulSW]

Roger, thanks mate. I've tried to look for leaks before and seen nothing, but at least now I've somewhere specific to look. Will have a mooch around later in the week 

Paul

[Webby the Bear]

try playing with the heater settings whilst you or someone else watches the HBV. the leak will show itself right at the HBV 

[JamesV6CDX]

Happy to take a look with a view to resolving on Tuesday. Plenum off and coolant pressure test needed

[omega3000]

Thanks for all the input 

The steam due to low coolant levels after loss elsewhere suggestion sounds likely. it seems to vent from the drivers side of the bonnet a couple of inches from the windscreen.

On Thursday the coolant was really low, nothing in the tank. I bought 5ltrs of pre-mix and put around 2-2.5 in to bring it up to the level, then started the car and ran it for 5-10mins with the cap off to see if anything happened; it didn't. I drove to work, about 4mls/20mins in stop/start traffic. Checked the level before I left work, hadn't budged, drove home another 3-4mls in stop/start traffic. Same drive the following morning, I can't remember when I checked the coolant again but it was later that day, and it had gone down 1-2cms from the cold fill level. I had also checked the oil cap at some point and found a good old dollop of mayo, although I did read somewhere that this can happen under normal conditions with a lot of stop-start driving.

Could this drop in level just be due to air in the system working its' way around? If I top it back up and keep an eye on it, maybe it will level out.

I've also found over the last few weeks that the 'ECO' button has stopped functioning, I don't know if this might be related.


Paul

Try switching it on a off a few times , probably just the button 

[PaulSW]

Just in case anyone else has similar issues and is searching for info - the HBV was indeed pouring out coolant when the cabin temp was set low. I replaced it and it seemed a lot better, but unfortunately the car's failed it's MOT and is uneconomical to repair, so it's going

Cheers all,


Paul

[dbug]

Guessed it was hbv - intermittent leakage points to that

Sorry to hear about the MOT failure though - what did it fail on?

[SMD]

Need to sort mine but it has decided to play hide and seek