V6 Overheating - suspect water pump

[ThisIsTheSea]

Thanks, rita, for the link to the diagram - this helps hugely.

Would I have to drain the whole cooling system off to remove the thermostat, or could I just get away with a partial drain and bleed?

[mikeonb4c]

I've never heard of the anti freeze and water separating even when a vehicle has been left unused for many months. With the expansion tank cap off, when you rev the engine youn should see the level rise and fall as the circulation increases. You mention the gauge has moved to the middle: what does it normally run at?

I'm very interested in this tip, as I've long wondered how it might be possible to diagnose poor coolant circulation due to a failing water pump. Being realistic, how common is it for the water pump to suffer critical loss of pumping ability as provided the system is well serviced and clean, then its hard to think what could cause it to happen.

Anyone? If there was a reliable and simple diagnostic test for coolant pump efficiency, it would be a real breakthrough

[rita]

Thanks, rita, for the link to the diagram - this helps hugely.

Would I have to drain the whole cooling system off to remove the thermostat, or could I just get away with a partial drain and bleed?

Just drain to bellow the stat,if you have fairly new coolant and you want to save it just put it into a clean container.

PS just reread your post,it looks like the coolant might not be what it should (CLEAR)I would drain/flush and renew the coolant.

[teenmal]

I've never heard of the anti freeze and water separating even when a vehicle has been left unused for many months. With the expansion tank cap off, when you rev the engine youn should see the level rise and fall as the circulation increases. You mention the gauge has moved to the middle: what does it normally run at?

I'm very interested in this tip, as I've long wondered how it might be possible to diagnose poor coolant circulation due to a failing water pump. Being realistic, how common is it for the water pump to suffer critical loss of pumping ability as provided the system is well serviced and clean, then its hard to think what could cause it to happen.

Anyone? If there was a reliable and simple diagnostic test for coolant pump efficiency, it would be a real breakthrough

Simply disconnect the outlet from the pump,stand back and start the engine you will soon know if it is working or not.Let us know what you find when you try it.

[mikeonb4c]

Yes even I could work that one out. But seriously, diagnostic techniques less drastic and coolant wasting are what I had in mind. For example, pressure measurement downstream of the pump, maybe simply by testing firmness of a relevant hose etc. etc.

[Simon Jones]

Thermostat housing can be seen here (viewed from below with the plastic undertray removed)



As I mentioned earlier, you should see some movement of the coolant in the expansion tank when the engine is revved which indicate circulation is occurring. If you want visibility of coolant flow, the only thing I can suggest is fitting a clear polycarbonate tube into a section of one of the main pipes. This was something that Ady (Northern Bongolow) was considering doing a while back to see that the the stat was opening.

Presumably, the main serpentine belt is present & in good condition & there are no other symptoms to indicate belt problem such as heavy steering and charge light showing?

I would drain the coolant, change the 'stat & pump, flush, refill & then bleed as per instructions for the diesel engine.

[teenmal]

Yes even I could work that one out. But seriously, diagnostic techniques less drastic and coolant wasting are what I had in mind. For example, pressure measurement downstream of the pump, maybe simply by testing firmness of a relevant hose etc. etc.

Normaly if you are at this stage of the game the coolant system has a problem,and undoubtedly the coolant would be changed as a matter of routine.If you want to save the coolant use a Bucket.

[ThisIsTheSea]

As I mentioned earlier, you should see some movement of the coolant in the expansion tank when the engine is revved which indicate circulation is occurring. If you want visibility of coolant flow, the only thing I can suggest is fitting a clear polycarbonate tube into a section of one of the main pipes. This was something that Ady (Northern Bongolow) was considering doing a while back to see that the the stat was opening.

Presumably, the main serpentine belt is present & in good condition & there are no other symptoms to indicate belt problem such as heavy steering and charge light showing?

I would drain the coolant, change the 'stat & pump, flush, refill & then bleed as per instructions for the diesel engine.

No movement at all of coolant in the expansion tank when revving the engine. No warning lights and the belt seems to be in good condition. The new pump arrived this morning. Thermostat is arriving tomorrow. Hopefully, I should be able to have a crack at this over the weekend.

The steering did go heavy a few weeks back, but I squirted the universal joint with liquid grease and changed the PAS fluid and was fine again. Have also recently done drop links, engine oil and filter, and changed transmission fluid.

Thanks for the info and for the pic.

[mikeonb4c]

Thanks Simon and Ady - useful suggestions. I'm thinking of the case where coolant and everything else seems fine, but pump is not circulating efficiently. An engine block temp gauge might give indirect warning once the problem has developed, but a direct warning at an early stage would be best.

[ThisIsTheSea]

Gawwwwd. I wish I had never started this!! Cannot seem to get the cambelt cover off to get access to the water pump bolts. It's just buried in there. I have removed every bolt I can see on the cover. It lifts at the edges, but the thing just won't budge.

New bearings are needed on a/c tensioner and alternator/water pump tensioner and also new belts needed. I think this is what was causing the engine whine.

[ThisIsTheSea]

New Thermostat. New Pump. Correctly bled 'til fan on and bottom hose hot. And still the same problem..... comes up to temp, fan comes on and then does not go off. Went for a 20 min drive and temp needle started climbing to 12 O'clock, stuck the heater on full and then it moved back to 11 O'clock, but fan still on all the time. May be radiator?

Fed up.

I'll leave the topic here and find a garage to sort it out. Adios and thanks for the suggestions that got me this far.

[windywatson]

Hi,
You didn't say that you had done a coolent system flush when you did all of the work on the system, did you? If not that is what I would do next as you may have a rad that has some of the gallaries blocked or restricted.

By the way you could have been unfortunate enough to have insatalled a faulty thermostate, it has been known to happen.

Cheers

[Northern Bongolow]

try a new cap on the expansion tank, if its not holding the correct running pressure this will lower the coolant boiling point.
try changing to red coolant, this may also help control the temps a little as it has a higher boiling point.

cheap things to try and may just sort it.
around half the caps i test fail to hold 1.1 bar. the fan switching point in pressure terms is only just under 1 bar so if the system isnt holding enough pressure it may start to boil the system.

[ThisIsTheSea]

Thank you windywatson and Northern Bongalow.

Not one to be defeated, I tried bleeding it again this eve (before reading your replies). I am following Haydn and Kirsty's video on Bongo bleeding. My V6 doesn't behave in the same way as the diesel does in the vid. When I increase revs, the coolant climbs up the funnel, whereas in the video the coolant moves down the funnel and into expansion tank. When the fan comes on and (presumably) the stat opens on the V6, things get semi-explosive with steam erupting from the funnel. By the time the fan goes off, it calms down again. I bled it for 2 hours this eve, with it behaving like this. But, while doing this, it doesn't overheat; I was buoyed by this, so went off for a test drive and it started overheating again. So when the system is pressurised, the overheating happens.

windywatson - you are correct, I didn't do a system flush. The reason for that is that when draining off the coolant there was no crud at all - relatively clear. My Bongo has done approx 65000 miles and has had quite an easy life - all pipes seem Ok, so I (perhaps wrongly) assumed that it was unlikely that there were any blockages. If I attempt anything further on it - I will do a flush.

Northern Bongalow - thanks for the tip on the expansion tank cap. Both radiator and exp tank caps are in good condition, but options are few at the moment so will definitely try that.

[teenmal]

When you drained the coolant was it clear as you stated earlier on.....Quote fluid in the coolant tank is now clear (used to be blue).

.