Persistent overheating - not obvious!

Shakes · 2017-01-30 19:28:49

Just got my Dispatch 900 2.0HDi back from my truck engineer friend who has had it for several months, trying to find the cause of persistent overheating/coolant loss....

OK, from the beginning: the van initially overheated on a 20-mile run, and the hose to the thermostat housing popped. Fixed that.

Then, on another long run, the cooling system pressurised and blew the water pump. Total coolant loss....replaced water pump and timing belt that time.

And then, on a 30-mile run, the system pressurised again and boiling water emerged from the top right hand corner of the radiator as you look at the front of the van.

This all turned my hair grey. Into the workshop she went for a thorough examination. Pressure testing and internal examination revealed no cracks in the head or block. We suspected the head gasket, but a CO2 test and thorough examination of the oil and water ruled that out.

Then, we looked at the thermostat and that was rusted shut. Would not open when tested up to 120C....thermostat replaced.

The van was then fully serviced and MOTd, then driven around for over a hundred miles and suffered no further coolant loss....until tonight, when I went to pick her up. Less than 500 yards down the road, on came the coolant light, up went the guage to just past the 70c point before dropping back down. Got home and there has clearly been coolant loss from the radiator, same place as before, but the system does not appear to be pressurising as before.

So, my questions are, what is happening here? Could it be that the thermostat was causing the system to pressurise, and that has blown a hole in the radiator? Is it worth fitting a new rad?

The engine has done 178k and runs smoothly and as I said, my engineer friend is convinced the head gasket is intact. Help!

Casper · 2017-01-30 19:57:11

Have you ran it without a thermostat to see how it goes?

Shakes · 2017-01-30 19:59:34

No, I haven't. It has a new one so should operate normally?

OAT · 2017-01-30 20:24:39

Surely shouldn't be pressurizing enough to blow at just over 70 degrees?

Isn't around 75 the "normal" temp?

I am sure you must have flushed it and it appears to have flushed itself but could some lumpy contaminant or debris be being picked up and still be intermittently blocking the flow? A reverse flush perhaps?

Clutching at straws here.

Last edited by OAT (2017-01-30 20:26:17)

Casper · 2017-01-30 21:29:21

Yip i would say probably blocked shit somewhere. Im sure thermostat is the only closed part. Take it out and if t happens again go for a back flush but dont just open a pipe and pump water through. Open a few. Radiator, Block, Matrix. I am sure you can get a flushing fluid. How is the cab heater? Working OK. If a tad chilly your matrix could be rotting inside out and part blocking. You could get a link pipe/hose and bypass that easy enough to eliminate. I would wait till warmer times first lol

Shakes · 2017-01-30 23:20:45

The system has been backflushed a few times already but it's something I'll try again.

Thing is, I think the initial overheating was the cause of all three blows - hose, water pump then radiator. We're fairly confident that the thermostat being rusted shut caused the pressurisation, I had assumed that when the rad blew, it was some sort of pressure release screw that blew out. My mate has a theory that once this screw blows, the radiator itself is scrap. Wondering if anyone else has heard of that.

Either way, I think the pressurisation has now been cured. Or at least that's what I'm hoping. too early to tell

Casper · 2017-01-30 23:52:54

Finger crossed then. Bet you never take your eye off that temperature gauge. Mine say at just under half way but i had the 1.9 non turbo

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#1 2017-01-30 19:28:49

Persistent overheating - not obvious!

#2 2017-01-30 19:57:11

Re: Persistent overheating - not obvious!

#3 2017-01-30 19:59:34

Re: Persistent overheating - not obvious!

#4 2017-01-30 20:24:39

Re: Persistent overheating - not obvious!

#5 2017-01-30 21:29:21

Re: Persistent overheating - not obvious!

#6 2017-01-30 23:20:45

Re: Persistent overheating - not obvious!

#7 2017-01-30 23:52:54

Re: Persistent overheating - not obvious!

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