Strange Over Heating on a 1.9 Petrol

[melvin]

Hi All,
I have a strange over heating problem on my 1.9l Petrol bus.
With the thermostat in place after around 10 mins of driving the temperature gauge reaches around 3/4 but the radiator is still stone cold. heater works fine though.

Now, The thermostat that was in the bus when I bought it had 6 hole drilled around the outside of the stat. If I put this one in the temp gauge reads around 1/4 when driving but if I leave it stand ticking over it slowly rises and when it reaches 3/4 the fan kicks in.
Using the bus with the holey thermostat the systems seems to function as it should, although a bit cold when driving, but with a normal thermostat in its as if the thermostat isn't opening. When the bus is over heating (3/4 gauge) the big pipe coming out of the top of thermostat housing going towards the radiator is stone cold which to me would indicate that the stat isn't opening but I have tested it in a pan of boiling water and it seems to open ok.

Has anyone ever come Across this problem and/or is it ok to run the engine with the modified thermostat?

Cheers in advance

Melvin.

[Ian Hulley]

A s/h engine I bought had had 8 holes drilled in the thermostat ... and 4 of them blocked up again with tiny nuts & bolts I'd be replacing it with a new one from Mr Baxter

Ian

[billy739]

place your location in your profile , a member may be able to pop over and help.

if your in gloucester i may be able to check....

[melvin]

Hi Ian, I have bought a new one from justkampers, tested in a pan but when it is in place the top pipe going to the radiator doesn't seem to get hot at all. With the stat in place and the top cover of if you try and push down the centre it only seems to go down around 5mm before it stops. do you know if you can get different types for early and late watercooled with more clearance on the bottom?

Thanks for the offer billy, but I live in sunny Cornwall, a little too far for you to travel I guess?

[Ian Hulley]

Fit the new t/stat, bleed the thing correctly and see how you go.

Ian

[melvin]

Hi again all,
I bought another new stat today just in case the other one was faulty/slow at opening, but still the same problem.
The thing thats concerning me is that with the thermostat that has the holes in if you leave it on tick over until the gauge read around 3/4 the fan kicks in, but if I put in the standard thermostat in the fan doesn't kick in at all and the water at the top of the radiator is stone cold! My only thought now is that the gauge isn't reading correct but I would have thought that after a 5 mile drive the water would be hot enough for the stat to open and flow to the radiator. Has anyone ever had a problem with inaccurate temp gauges? or know of any way to test them?

Cheers

M

[cascais]

hi m...i have the same prob with mine and its doing my head in trying to figure out the prob!im in portugal so the extra heat doesnt help.i had a new thermostat fitted and like you the pipe from the therm wasnt as hot as id expected it to be,but the rad was getting hot so it must be opening.ive checked the temp gauge and there are two voltage regulators that i think need replacing,as the needle goes to 3/4 and sometimes above that ,but the fluid in the tank doesnt feel that hot when you touch it.ive also bleed the system as per wiki,and fitted a switch to put fan on from inside van,as i was afraid it would overheat.so far it hasnt and the guys in my garage have said there is nothing to worry about,but im going to try and get bits for temp gauge and fix that.im no expert on these vans as this is my first,and only had it a few months,but i thought id share my prob wth you as yours are similar....

[ambivert]

I had similar problems with my 1.9 petrol DG. All sorted now.
To cut a *VERY* long story short, just get yourself a digital waterproof pen thermometer - I got one of these for just over a tenner - http://www.thermometersdirect.co.uk/aca ... meter.html" onclick="window.open(this.href);return false;

Then, you'll need to find a way of running your engine with the thermometer probe in the coolant (as near to the stat as you can get it)... I drilled a hole (4mm diameter) all the way through the central shaft of the temperature sensor (which is screwed into the engine block next to the stat) and just popped the thermometer probe thru the hole (smeared with vaseline to prevent leaks because its only 3.5mm wide). DO NOT DRILL IT WHEN ITS STILL IN THE ENGINE

This does, of course, destroy your temperature sensor. So get a replacement first. Alternatively you can find something with the same size and thread as your temperature sensor (maybe an old broken one) and drill the hole thru that instead. I'd recently replaced my sensor with a new one from GSF, so I drilled the old one.

Anyway, I ran the engine (normal idle is fine) and the thermometer proved that it was NOT overheating. After running for 10 or so minutes, the stat opened, the rad got warm, and the fan eventually kicked in around 95C, IIRC. This also proved that my new sensor from GSF was a piece of crap, and was reading too high. This annoyed me, so I replaced it with a genuine VW sensor, which works perfectly.

Oh yeah, I also found that my stat had been butchered (half of it has been removed) so I replaced that with a genuine VW one too. That solved all manner of problems. I personally would NOT run the van with a dodgy or non-genuine stat, only the VW ones work properly, they are much more complicated those you'd find in most other vehicles.

[melvin]

I Think I have located the problem.
Done as you said and inserted a thermometer into the hose just before the thermostat. It reached around 60 deg then the pre heater relay clicked of as it should but the gauge in the van was reading just over half way. Kept it running until the thermometer read 77 deg, by then the gauge in the van was reading just under 3/4 I wanted to keep going until it read 88 deg so that I could check the thermostat but the water pressure got too great and my makeshift thermometer in hose setup started leaking, but it was enough for me to decide that the gauge is at fault. Next thing to do is replace the gauge but presumably they are a bit hard to find. I was thinking of putting in an aftermarket gauge, I have plenty of smiths ones lying around in the garage but does anyone know if they are all universal or would I need to install another dedicated sender for it?

[Ian Hulley]

Get a s/h gauge or a set of clocks off Billy numbers .. he's usually got them for sale.

Ian.

[ambivert]

It might not be the gauge, it might be the sender, which is faulty.
The sender would be much cheaper to replace, even using a genuine VW one, which IIRC still only cost about a tenner.

[collins_sh]

lads I had the same problem, always use genuine stats and gauges/sensors as for the sake of an extra tenner you could fry the engine.
mine runs just barely on hot side of led and i used to drive the missus mad demanding that the cabin heater be on at all times. i now concede that it isn't overheating.

just a note when bleeding, mine is an early water cooled motor, ie stat housing facing down with a bleeder up high on outward/return lines to rad.
this bleeding needle valve can block up, its no harm to crack the highest jubilee clip on each of these lines to expel any air in that part of the loop. if they had ran those 2 lines under the clutch bell housing bleeding wouldn't be such a slow process on these buses.

also one small hole in the thermostat housing will help bleeding of the system (tiny hole), a lot of large holes will allow cold water circulate around the thermo diagrapham telling it that the engine is cold. and may do more damage than good as the pump outlet line to the rad will not get isolated when hot and send hot water recirculating around the engine block.
if you still want to modify the stat, press open the valve and drop something into the bushing at bottom that will not allow it to fully close.

just check for the obvious signs of bubbles when reving engine to signify head gasket/jacket failure.

VW G12 antifreeze/coolant is the stuff to be using on these wagons