New overheating problem (diesel) on road trip

[therealchrisgray]

I hope someone can help, I'm on a long journey and have hit a snag.

I just packed up and hit the road out of the town where I spent the night, and ten minutes down the motorway noticed the temp gauge was beyond its normal point. And the red light was flashing directly behind it.

Needle normally only moves 1/4 of the way left to right, now it was vertical. It kept going, and I was on a long stretch with no exits, so I put the heating on full. The needle crept back from right to vertical again until I found pull off - where I am now.

I guess the heater means the radiator is hot, so coolant is moving, although I couldn't hear any electric fan running.

I've half-emptied the van to get at the engine bay, and coolant reservoir is at normal level and not venting. No water under the van, no sign of coolant inside the engine bay, but some oil on the left side of engine and dripping onto the ground underneath. It looks to have come from the filler cap on top of the engine.

I did top up the oil via the filler behind the number plate before I set off this morning, but the level is still between the dots on the filler. On the low side rather than too full. I just checked it again now, seems normal.

Does anyone have any suggestions?

I was just trundling along at 80kmh, 50mph, not flogging it.

Engine is an old diesel allegedly from a 1980s Jetta, no turbo.

Outside temperature today is noticably lower than it has been for the last few weeks and less direct sunlight.

Can anyone suggest where to look or how to proceed? I have a commitment 600km away in 24 hours so I do need to push on even if it's at a walking pace. Can the engine survive being run at this elevated temperature for a long period?

Thanks in advance for your advice. This forum has been invaluable!

[davidoft1]

can you hear the cooling fan ?

[Stesaw]

Was the radiator hot?

[therealchrisgray]

Aha! Radiator is cold to the touch after driving another 30km.

Under floor in cab is also cold, so no coolant flowing?

Does that mean water pump is dead?

[therealchrisgray]

That'll be why I can't hear the cooling fan.

[davidoft1]

Either an air lock or a stuck closed thermostat

[therealchrisgray]

Either an air lock or a stuck closed thermostat

Thanks for that. I've removed the casting from the top of the engine, the one with all the water pipes connected to it, but no thermostat inside. Is it somewhere else or has it been removed previously, do you know?

Weirdly, I've just started it up from near cold and the flashing red temperature light came on straight away. It hasn't gone off even though the temp needle hasn't moved yet.

Any suggestions on clearing air locks?

Water pipes to the radiator were warm to the touch close to the engine, but not hot. And cold further forward. I guess that's just ambient warmth from the engine bay?

Keep the suggestions coming please. I'm going to have another go at driving towards my goal, not a lot of other oprions right now and at least it's getting colder.

[Stesaw]

Open the bleed valve on the radiator with it running and see if you get any air out of it. It should be hot all over when the engine is up to temp. Also check your heater, if that doesn't go hot or it goes hot cold hot cold then you got air in the system. so you'll need to top up the coolant.

[therealchrisgray]

Open the bleed valve on the radiator with it running and see if you get any air out of it. It should be hot all over when the engine is up to temp. Also check your heater, if that doesn't go hot or it goes hot cold hot cold then you got air in the system. so you'll need to top up the coolant.

Thanks for this. Can you believe the fault just spontaneously cleared itself last night?

I stopped for a break and fuel up, topped up the oil, and it rained for the first time in weeks. When I got back in there was no warning light and temp has been fine since then - 300km ago.

Heater was running hot yesterday, kept it on all day to keep the engine that bit cooler, but seems to have its own water system. There's a pair of separate (smaller) pipes running alongside those to the radiator which were hot.

So yeah, it's all a bit of a mystery. Could it just be a problem with the temperature sensor?

[therealchrisgray]

Could it just be a problem with the temperature sensor?

Scratch that, the radiator was cold to the touch. So were the water pipes feeding it. Air lock that magically cleared itself?

[sarran1955]

Hello,
I don't often venture into the water-cooled world.....

However a few years ago an English couple came to me for help with their overheating Diesel T3.

It would run fine on tickover and on full thrash, all bled, hot pipes etc. But after a few Kms of steady driving, the temperature would shoot up.

In the end I changed the timing belt and water pump, problem solved.

The interesting thing was that the pump impeller was plastic and had broken the bond with the metal driveshaft, so all was well on testing,but no good on the road. Had we not had a new pump, it would have been possible to glue prop to shaft to get out of trouble.

I even did a little video:



Air-Cooled Bliss...

Cordialement,

[therealchrisgray]

The interesting thing was that the pump impeller was plastic and had broken the bond with the metal driveshaft,

That sounds like the right sort of explanation. Impeller losing its grip for a while and now something has "snagged" so it's working OK until the next time.

Assuming I get to where I'm going next week then that sounds like something to look into. 500km more then I'm mostly stopped for the next six months, time to tinker.

Must admit, I'm enjoying learning my way around my new van!