Coolant probs - again

diesel dunk · Post by **diesel dunk** » Sun Feb 26, 2006 3:47 pm

Hi, my coolant system still appears to not be working properly. The gauge goes through the mid way and up to top after about 10 mins ans stays there. The coolant fan never kicks in, it does worl 'cos I've shorted it and it spins - although the thermos switch could be bust I suppose. Anyway, I have drained the system b4 and took the chance to remove the rad and check it wasn't blocked - seemed ok. Tested the the thermostat and is ok. One pipe going to rad from head does eventually get warm after a long run, but pipe coming back from rad is stone cold. Does this suggest air-lock (I have bled carefully on a gradient etc) or knackered water pump, or blocked rad or what. Any advice very appreciated on simple tests. Cheers, Duncan.

libbybapa · Post by **libbybapa** » Sun Feb 26, 2006 7:30 pm

I would certainly check the waterpump if you haven't. Wasy to remove and replace. The draining and refilling of coolant is the only hurdle. Overly advanced inj timing can cause hot running as well. Did you use the dial indicator to set the timing?

Andrew

diesel dunk · Post by **diesel dunk** » Mon Feb 27, 2006 8:51 am

No - I haven't set the timing, other than to just mark the belt and put it back exactly where it was after head gasket change - there is no smoke either. Also, the coolant gauge has always shown too hot since I bought her in Oct. What really worries me is that the hose coming from the rad back to the water pump is stone cold - surely this should still be hot, just not as hot as the one coming in eh? and this would resolve why the thermo-switch never turns the cooling fan on - surely the rad isn't so efficient that the coolant is really cold when it leaves the rad. What do you think? Have just read you pm - thanks for reply, if there was no flow because of a blockage, wouldn't the energy from the hot water eventually find it's way down to the rad from the head, even without convection flow. Also, I don't get any screeching noises from the water pump, which I have read can happen if the impeller is loose etc.

libbybapa · Post by **libbybapa** » Mon Feb 27, 2006 11:06 am

I have seen stamped steel impellers (fairly common). They are junk. The impeller can wear away so that there is very little moving the coolant. Is the gauge itself in question? You would need to have a fair amount of flow with open thermostat to move all of the coolant from the radiator back to the engine possibly more than 10 minutes. When the van is hot and you open the bleeder valve, does coolant come out, or air?

Andrew

diesel dunk · Post by **diesel dunk** » Mon Feb 27, 2006 11:21 am

no air comes out - I have been careful to bleed the system as you described b4 - not sure if the gauge is dodgy, I can get hold of one and try, but my main concern is that the pipe coming from the rad is always cold and the thermo switch doesn't even turn the fan on...

stopping · Post by **stopping** » Tue Feb 28, 2006 12:35 am

Hey there folks,

Have you taken the water pump belt off and checked it for play and free turning? Sounds like water pump. I think the bearings puke with these things and the impeller is further than from the walls of the pump body and the pressure drops. Water pump for these things is 20-30 bucks depending in which country you live.

If I remember, you already checked for air bubbles in the coolant tank yes?

Just in case...... start the engine from cold and leave the cap loose till the coolant rises and you need to close it up 10min. Watch for continuous small bubbles coming from the top hose. It's a sure sign of a head gasket leak. You should also be able to see turbulance in the water which will tell you if your pump is pushing at all.

Just some thoughts as I have had a failed pump and a head gasket failure in my life with the vw diesel.

Steve

diesel dunk · Post by **diesel dunk** » Tue Feb 28, 2006 11:50 am

ok here goes again - did what you said - ran up to temp with expansion cap off - no bubbles - some turbulance, increasing when engine revved - all sounds normal - the thinner coolant pipes going to and from the dash heater are both hot the whole length of their run - this suggest also that the water pump is working. I have tested the thermostat also, and this opens at the specifies temp - only just the tolerance allowed, but still does its job, I guess. The only thing I can think is that the rad is blocked, as previously mentioned, the return hose back to the pump is stone cold. However, I have had the rad out and flushed it with water to check, and it seems fine (held a hose and rag over one end and water squirted out of the other) but, I still suspect there is no flow in the rad for some reason, as the thermo-switch never activates the fan, even when temp gauge goes to max and the vehicle is stationary (therefore no airflow to cool rad) could still be airblock in rad, but there is coolant pissing out of the bleeding screw and no air) - hmmmm. I'm stuck now - don't want to pay mechanic any $$$ (Â£'s) - I don't suspect the gauge, as the engine definately operates better when the gauge needle is in the middle, but it then advances to max and beyond, where the van seems to not be running quite as good.

diesel dunk · Post by **diesel dunk** » Tue Feb 28, 2006 12:25 pm

thinking about it, how large should the turbulance be in the expansion tank, because it was never a great surge, and there is a very long run up to the radiator, with lots of ups and downs (as you know) so can either of you tell me how great the turbulance should be (should it be a great flood of pressure that splashes all over the place) 'cos it wasn't...

stopping · Post by **stopping** » Tue Feb 28, 2006 1:17 pm

Duncan

Sounds like your in need of a mechanic.

You have flow but didn't check for bearing play. If you checked your themosat in the water pump you may have noticed the impeller free turning and no end play. Sounds like everything leads to the thermostat or the gauge but you should consult a good mechinic.

Maybe you put the thermostat in backwards. Maybe there is air by the thermo dunno but that would keep it from opening.

The rad fan almost never goes on... good thing, sounds like it works...these engines (diesel) rarely get hot enough to trip the fan. (I do live in Canada and go north every summer so I think I can count nymber of times the fan has kicked in.)

Thats to say you need to mesure the real temps of the coolant.

Sorry I can't help more

hoyt · Post by **hoyt** » Tue Feb 28, 2006 2:07 pm

Have you check to make sure that the long pipes running up to the rad
are clear?

It sounds like your heater works, is that right?
If you turn the heater on full heat and high fan does the
temp gauge still go to max when idleing? What if
you rev the motor a little? If so I would
replace the temp. sender, they are cheap.

I would also replace the thermostat. There is more
to a T-stat then opening temp. There is how fast it opens, how
wide it opens, closing temp., how fast it closes, etc.
I consider T-stats a wear item and replace when I replace
the coolant.

I had a lot of problems on my Vanagon with slipping belts.
The outside half of the two piece pully on the water pump
would bend and make the belt loose. It was so bad that
if a turned on the headlights the van ran hotter due to
the slippage!

Good luck.

diesel dunk · Post by **diesel dunk** » Tue Feb 28, 2006 3:49 pm

ok - thanks for all your advice - tomorrow I will check the belt and if ok check the bearings in the water pump and probably order a new T-stat anyway, but I'm still confused at how the pipe coming from the head to the rad is red hot and the one coming back from the rad to the pump is stone cold - the temp sender unit is new and the gauge goes to max when the wire is grounded, so that would suggest both the circuit and gauge are ok. I will also test the coolant temp with a thermometer if I can find one, as far as the bentley suggests the t-stat should open at 80deg C and be fully open at 94deg C, I will check this too. I still favour a blocked rad or air-block in the long pipes, but it can't hurt to investigate these other things - might learn something too... Cheers for all the advice.

libbybapa · Post by **libbybapa** » Tue Feb 28, 2006 4:05 pm

If it is actually overheating and gauge is reading accurately, then the hot pipe to the radiator and cold from would indicate slow flow IMO. It could be a blocked radiator, but it could also be a bad/eroded waterpump impeller or some other problem with the waterpump, or even a stuck or semistuck thermostat. Considering that the thermostat and waterpump combined ar far, far less expensive than the radiator and also easier to change, it makes sense to me to adress those first. Unless you're a "the sky is falling" personality type.

You can inspect the waterpump and radiator, and test the thermostat, without any outlay other than the labor.

Andrew

diesel dunk · Post by **diesel dunk** » Tue Feb 28, 2006 5:24 pm

yes, I will do this, although - as I said - I have tested the thermostat and it was fine in a pan of boiling water - having taken the pump, t-stat and radiator off before, I would have to disagree with which was quicker - I dropped the rad out in about 5 minutes, but taking the pump pulley and fiddly bolts from underneath took me ages...

.... and the sky isn't falling just yet - in the 5 months since owning the van I have learnt loads, (I knew nothing about mechanics back in Oct) but you have to admit it is frustrating when there are several possible sources of a problem, which makes it hard to decide what to test and when to cut losses and buy new -poor me eh? Anyway, this forum is really useful for help on that.. Cheers people.

diesel dunk · Post by **diesel dunk** » Tue Feb 28, 2006 6:47 pm

Thought of a test - I have mapped out my coolant system and the path via the oil cooler and back to the thermostat side of the pump only has flow once the t-stat is opened. This circuit piggy-backs into the pipe coming back from the radiator - so, if after warming, this circuit gets hot but the pipe from the rad is still cold further up, then this would suggest that the thermostat is doing it's job, and the pump too (to a degree atleast) - what do you think?

libbybapa · Post by **libbybapa** » Tue Feb 28, 2006 6:55 pm

I have a recollection that you switched your radiator hoses a while back. Did you ever switch them back to the stock setup? I think that if you put a thermometer in the expansion tank, it will overflow as the water in the radiator is above the expansion tank. You might try it though to verify a hot situation. Ever get any boiling coolant? If it is overheating then perhaps tackle all at once. Pull radiator and take it to a radiator shop to check it out, pull waterpump and inspect and pull thermostat to be sure it is in correctly. If you try to remove the waterpump to waterpump housing bolts be aware that they like to snap. Heating the housing with a propane torch where the bolts thread in would be very worth doing in this situation. Yes, it can be frustrating. No offense meant on any of my comments.

Andrew