half an hour holiday (overheating)

[redsnapper]

Hi,

Was nicely lined up for a trip to Cumbria and possibly beyond - got less than half an hour from Brighton and van overheated.

It has shown no signs before, and it was an exceptionally hot day, but when we called out breakdown they said they suspected a possible head gasket failure

The breakdown guy bled the radiator (thought it may be an airlock), put radweld in the system and filled it up with water. Little test drive and temperature held steady, radiator getting warm so water circulating. Off we went feeling optimistic, then onto the motorway and needle rising within a mile.

Long story short, tow truck of shame home....

Is there anything else I should be trying before getting it towed to a mechanic (presuming I can find one who isn't booked up for the next three weeks!)?

1.7 watercooled diesel. When I looked at the watertank after the second overheating there was some nasty brown sludge floating on  the top (guessing from the radweld?)

Thanks,

Ian

 

[937carrera]

Not a diesel expert, but given your predicament some ideas:

Radweld, uurgh. I would be tempted to drain all the coolant off to get rid of it.

As you are doing that then make sure the thermostat / thermostat housing are fine. Swap the thermostat for a known good one, or a new one

Is the impellor on the waterpump steel or plastic and how new is it...... if the engine is still based on the old VW petrol (I think it is) the plastic ones used to fail gracefully, still pumping something, but not sufficient

Flush the system and refil with water. Get it up to temperature, bleed and see if it is stable on idle. If so run and hold the engine at 2000 rpm or so and watch the header tank. Lot's of air bubbles going in and it's almost certainly head gasket. Watch the exhaust for condensation even when the engine is warm, that's another sign.

Good luck, much nicer weather in the North

[colinthefox]

As said, check the thermostat. It's a different water pump to the petrol engines, so impeller slip is possible, but unlikely. Check the radiator, might be full of insects, or crumbliness/corrosion of the fins at the bottom of the radiator indicates failing radiator core. Flush out the radiator internally (both directions) into a bucket and see how much brown stuff you get out.   Before you consider tearing the engine apart, best make sure the brown sludge isn't due to the oil cooler/warmer (above the oil filter) leaking between the oil and water sides. Test this by removing and joining the coolant hoses at the cooler together with a short length of pipe. Run the engine. If that is the problem oil will drip out of the water connections with the engine running. Check the coolant pump belt is tight, and that the pump pulley and belt are not worn. If the belt runs down on the valley of the pulley due to wear, it will slip, and no amount of tightening will cure it. Particularly relevant to these engines as the pulley takes the strain of running the alternator as well.

Cooling problems can be a combination of any or all of the above marginal problems, which on a hot day with heavy load will take the cooling system over the edge.

When you've eliminated all of these, only then start considering head gasket problems. Not saying it's not that, but all the others are much cheaper and simpler to put right.
 

[redsnapper]

Thanks guys,

Some good ammo there to help fault find, and a lot of learning to be done my me in the process. Will have a proper read through and break it down step by step and look up the knowledge needed.

Yes, did wonder about the radweld myself, especially when seeing the brown sludge!

Seems like the VW gods and law of sod were against us yesterday...

[silverbullet]

Brown tarry goo can be a sign that old glycol blue or green coolant has been mixed with modern pink/purple.
It doesn't wash out. Petrol doesn't dissolve it, brake cleaner might or you may have to use meths (experiment required)

[redsnapper]

After a bit of further research, am I correct in thinking that if the radiator is getting hot and there is hot air blowing from the fans that I can rule out the thermostat?

Cheers,

Ian

[937carrera]

Probably, but not necessarily.

The thermostat could have failed so that it allows some flow to pass (so the rad etc gets hot), but not enough to get sufficient flow through the rad for cooling.

[Mr Bean]

After a bit of further research, am I correct in thinking that if the radiator is getting hot and there is hot air blowing from the fans that I can rule out the thermostat?

Cheers,

Ian

Yes it looks like it and here are a few simple things to check (Hope not teaching granny to suck eggs )
Be absolutely sure the thermostat is a good one - use boiling water. ( while obviously not good practice in the long term, removing the thermostat is OK just for diagnostic purposes and can give a clue if a replacement is not immediately available. Not necessarily a good idea if the the large "O" ring is in place of a gasket as no seal may be possible. (used to be a trick to get  home in the absence of breakdown recovery)   Make sure that every bleed point lets out either air then water or just water when the system pressurises after a refill/top up. As it warms up from cold you would hope to see some coolant flow if leave the cap off and you rev the engine. Leave the cap off for the moment and go round squeezing the larger rubber pipes which should be cause the coolant to rise slightly as you squeeze each one. You may be able to feel the coolant squishing inside. Replace the cap and turn on the heater and blower on to indicate if and when the stat opens as comes up to temperature. Flow can also be checked by feeling the top and bottom of the radiator. There should be a noticeable difference - top hottest but either one at ambient indicates no flow. Assuming it has an electric rad fan does it switch on at any stage of the overheating? The comment regarding fin shedding or boss slipping in plastic rotor water pumps is a possibility (It happened in on one of my cars and took a whole load of sussing).
Keep us updated.
 

[redsnapper]

Thanks very much, and learning to suck eggs as I go so all help appreciated!

Was looking at this as a guide to removing the thermostat and testing it, which seems to tie in regarding the boiling water test. So reckon that is first port of call. , Interesting part kicks in around the 4.45 mark:
https://www.youtube.com/watch?v=Wze4EqIbbQs

Also like the idea of getting the brown sludgy stuff out and clean water in so I can see if there are signs of oil and just because what is in there at the moment looks distinctly unhealthy.

Guess if I get to the thermostat I can expect a lot of that water to empty out with no choice in the matter Just going to have a little test this evening to see if things want to loosen.

Still a bit puzzled as to the radiator flush part, pretty sure there is only one bleed nozzle on this model (top left as you're facing the vehicle), but one step at a time especially as it is freakishly hot at the moment!

Will keep plugging away. Actually... first step is to remove all our sleeping bags and swimming gear from the back to get to the engine! slowly slowly...

[lefty67]

Is the overflow tank behind the flap full?

[redsnapper]

Hi, regarding the overflow tank, yes up to the max line.

Didn't get much further as started getting dark but had another look at the water in the header tank and not as turgid as I thought, slight bit of brown scum on the surface but only very little.

investigation to continue tomorrow...

I was also thinking about the main radiator fan, I don't think that was kicking in when it was overheating, but can't be sure (as was blasting out the main heater in the cab!). How much of a factor could that be?

Temp gauge didn't get past the three quarter mark as managed to stop as it was climbing (normally sits nicely on the half way mark once the enging is warm), but when we did stop there was water pumping out the small vent at the top of the overflow and that was steaming hot.

Thanks everybody for the info, ideas and support so far!

tbc...

[redsnapper]

slow but steady progress.

Left WD40 on the bolts overnight and gave them another spray this morning. Managed to get them moving and thermostat out.

No apparent movement in boiling water! Looks like this so stuck... open?



Thanks guys, so satisfying to be able to delve in to the problem! One step forward..

Will get another ordered and some decent coolant from Brickwerks
 

[Mr Bean]

Did I read you right?
Stat should start closed and open to regulate water flow. new stat will confirm.
 

[oilrag]

That looks stuck in closed position ,sealing off cooling circuit to rad etc.

[redsnapper]

Cheers, yes I think stuck in closed position rather than open from looking around and from Mr Bean's post. Puzzled then how radiator was getting hot!?

Anyway, great that you guys advised to not rule it out, new one on its way and now looking at how to empty the coolant and give everything a good flush.