Overheat query

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DaveH76
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Overheat query

Post by DaveH76 » Sat Oct 17, 2020 8:40 am

Morning all,

Last night I nipped out in my van. Drove it from cold for no more than a mile then stopped for just under an hour (the engine didn’t get fully up to temperature). On the way home I was about 500 yards from the house and I heard a strange noise, so I backed off the throttle and it remained and when I turned the engine off it died down. When I restarted the engine the noice came back so I carried on driving and that’s when I noticed the temperature gauge right up just about in the red. I limped the last 350 yards to home (the last 20 yards downhill with the engine off) and parked it up. When I lifted the bonnet the coolant was coming out of the header tank overflow. The coolant is a brown rusty colour and so not sure when it was last changed (although the previous owner bought it from Bongo Spares a couple of years ago and had taken it back there for all maintenance needed).

I have had the van since June this year with no previous cooling problems. The gauge has always been steady at just under half way and has not needed topping up (although because I haven’t done any long journeys in it I haven’t checked the level for a little while). One thing I have noticed since I have had the van is how quick the temperature gauge gets to normal running temperature - it doesn’t take long.

I think the reason it overheated was due to a blockage bearing in mind the coolant colour. The repair plan is to bleed the system, pressure test it, and probably replace the thermostat and water pump, backflush the engine and either backflush the radiator or replace it.

What is the collectives opinion on the cylinder head being cracked bearing in mind the distance i drove it with the gauge on max (no more than 3/4 of a mile)?
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g8dhe
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Re: Overheat query

Post by g8dhe » Sat Oct 17, 2020 9:50 am

Another cause other than blockage is pin hole leaks in the rubber pipes and at the connectors, because the system is pressurised you can get fine squirts of steam when operating that leave very little trace, then as the system cools down they suck in a air, after a few cycles of this then you get an air lock and overheat happens. I would suggest a good inspection of the all the hoses and pipes and any suspect ones replaced especially the larger hoses! If there is still no sign of a leak the UV dye and light kits from eBay can help locate the dye after it has sprayed out.
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Flanners
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Re: Overheat query

Post by Flanners » Sat Oct 17, 2020 9:56 am

Take it this is a diesel...given what you have described rapid warm up, the overheat/boil over and the colour of the coolant (coolant mixing with oil or exhaust gases), I would be considering cracked/HGF. What's the coolant smell and feel like?
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DaveH76
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Re: Overheat query

Post by DaveH76 » Sat Oct 17, 2020 10:47 am

Thanks for the replies guys. I was so engrossed in the detail I forgot the basics...so yes, it’s a diesel 1996MY!

The coolant feels and smells (and tastes..!) like normal but dirty. Doesn’t smell like it has exhaust contaminants in.

The rapid warm-up is / was a characteristic of the van so the fact that the engine was up to normal operating temperature after a couple of miles didn’t ring any alarm bells and did not throw up any issues during the previous use (including 2 weeks on holiday in it in the summer). Maybe this was actually an early warning sign regarding a restriction in the coolant system which has now resulted in a blockage?

A thorough hose inspection is also on the agenda - thanks Geoff. I am also hoping that any pin hole leaks will show themselves when pressurise the system after bleeding. The UV dye detector is also a good idea - I will look into this too.

So the general consensus is that no matter how far you drive with the gauge up to max the head will probably have cracked...?
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Re: Overheat query

Post by Flanners » Sat Oct 17, 2020 12:18 pm

spin the roulette wheel, you may be lucky if it's the 'first overheat'. Have a read of some previous posts on here the consensus seems to be that if the temp gauge has informed you of overheat and you have had a boil over the damage is done. You could get a combustion leak test to help with diagnosis... from the 'bay they around a tenner.

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g8dhe
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Re: Overheat query

Post by g8dhe » Sat Oct 17, 2020 12:23 pm

It does indeed tend to be a game of roulette! Some report immediate problems others seem to get away with it, I would guess it depends on just where the air gets locked in, how much air, how long it takes to boil etc.
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DaveH76
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Re: Overheat query

Post by DaveH76 » Sat Oct 17, 2020 12:37 pm

It’s definitely the first overheat problem I have had so that (may) be going in my favour...!

I suppose the first thing is a bleed and pressure test, and if there’s no leaks then run it up and see what happens. The metal pipes and top and bottom hoses seemed OK (gave it a thorough going-over after I bought it), no leaks in the footwell, nothing from the rear heater matrix. I will have a good look at the T-piece on the head and the associated pipe work from there too.

The plan was to drop and change the coolant anyway but I didn’t get around to it before this happened, so I will be doing this too if all shows OK and backflush the system and radiator and change the thermostat. Then it will be short runs around the town only for a little while...!!

The combustion leak detector is worth a punt too - thanks for the suggestion.

I have read the posts regarding overheating but they all seem to have happened when the drivers are away from home and tends to involve cooling off periods on the journey. I am hoping that, because I was so close to home so barely drive it in this state, I have gotten away with it due to the pressure building and releasing only the once....

Here’s hoping..... :shock:
Last edited by DaveH76 on Sat Oct 17, 2020 1:06 pm, edited 1 time in total.
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Re: Overheat query

Post by Bob » Sat Oct 17, 2020 12:51 pm

Fingers crossed for you. [-o<
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BongoBongo123
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Re: Overheat query

Post by BongoBongo123 » Sat Oct 17, 2020 7:20 pm

Yes, hope you get away with it and nothing too broke.
DaveH76
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Re: Overheat query

Post by DaveH76 » Sat Oct 17, 2020 9:24 pm

Thanks for the positive vibes guys - appreciated.

I managed to have a quick look earlier.....

So..when I bought the van I made myself a coolant dipstick and marked on it where the level was in the header tank. I dipped it again today and it has dropped...but the level now is actually the correct ‘full’ level for the coolant in the header. So it looks like what I lost yesterday was perhaps the excess coolant... When I looked into the header tank there was some residue floating on top but not sure what it was (definitely not oil through).

However, something certainly caused the pressure to build up and put the temperature to max. I have had a look at the pipes under the seats and bonnet and all fittings look fine with no signs of staining which would indicate a leak, so this is making me think even more along the lines of a blockage. I also had a good look at the head T-piece which looked fine too.

The engine block under the drivers seat has signs of oil running down it (which I think is coming from the head gasket - spotted this before I bought the van and put it on the ‘to do’ list), but earlier I have also noticed one of the core plugs on the side of the block looking a little ‘cleaner’ than the others which was not there before... When I get to pressure test the system hopefully this will either confirm or rule this out.

Are the core plugs a known fault with the Bongo Diesel engines?
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Re: Overheat query

Post by Bob » Sat Oct 17, 2020 9:52 pm

Never heard of core plugs being a problem, but others have more techie knowledge than me.
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Re: Overheat query

Post by g8dhe » Sat Oct 17, 2020 10:23 pm

I think there has only been one report of problems with Core Plugs that I can recall!

Be aware that pin hole leaks don't leave much of any trace, as the water is lost thru steam escaping thru the pin hole rather than drips. One way of watching for it is with the engine hot but on a cool/cold night, then with a strong pencil beam torch you can sometimes see the vapour escaping.
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Re: Overheat query

Post by DaveH76 » Sat Oct 17, 2020 10:38 pm

Thanks guys.

To be honest, I am half tempted to pull the head off it anyway because there looks to be an oil leak from it (trace of oil between the head and gasket joint and oil on the block but not above the head). It will also give me an excuse to replace the thermostat, water pump, the timing belt, and the camshaft oil seal.

I have read on the forums that the pipe work at the t-piece can chaff and spring leaks but these look fine and are not rubbing on anything. The metal coolant pipe work integrity looks fine too with no signs of corrosion, and there is nothing leaking underneath from the rear heater matrix either. Other than these spots, is there any other common leak areas on the Diesel engine?

Geoff - from your experience will any pinhole leaks show up on a pressure test?

Thanks for your responses to the questions thus far. I want to get a definite plan of action in place because I will have a narrow window of opportunity to sort this so I want to make sure the time I spend is as productive as possible!
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Re: Overheat query

Post by g8dhe » Sun Oct 18, 2020 8:59 am

The amount that comes out of a pin hole is quite small normally, which is why it takes several cycles of heating cooling for enough air to get sucked in so I wouldn't necessarily expect it to show up on a pressure test necessarily unless it was left for sometime at pressure.
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Re: Overheat query

Post by haydn callow » Sun Oct 18, 2020 9:04 am

Oil on block under drivers seat is pretty much normal and comes via the EGR. NOT A WORRY
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