The Mitsubishi Pajero Owners Club®

[NDZ]

Apologies, I know there are dozens of threads about this I've tried to read them all but have got a bit overwhelmed at how best to proceed. I know it could ultimately be a cracked head but I'm also hoping it could be something less serious.

My 2.8 LWB has started to overheat, only when towing a trailer on long stretches and I can't get it to overheat otherwise. The only consistent symptom is loss of coolant, a few weeks ago after a 40 mile tow I noticed the rad cap had sprayed coolant everywhere. After a quick inspection the cap was in pretty poor shape so I replaced it and thought that was the culprit, I used the Paj as a runabout for two weeks and didn't lose a drop of coolant. Next towing trip we are heading into the Welsh hills and I see the temp gauge climbing, pull over and find over a litre of coolant has gone somewhere, no obvious leaks so I wait a while, fill her up and try again. This time we get a mile or two before the same thing happens and now the expansion tank is full of boiling coolant. We survive the trip by going slow on the back roads where the temp stayed perfectly fine for 3/4 of the journey then raced up again at the lights with the engine not under any load or having just worked hard.

Looking through the posts about overheating I suspect there's more than one problem contributing to this. I'm planning to go through each one methodically but here's my list

Oil - not showing any signs of contamination on the cap or stick

Coolant - likewise not showing any signs of oil

Bubbles - rad overflow tube into a jam jar does appear to bubble, one every five or six seconds and I think I can see smoky gases coming out.

Rad & system - never been flushed in the two years I've had it, could be full of all sorts.

Pump & thermostat - not been serviced or checked lately

Front fogs - never thought of that but there are two large fogs taking up a fair bit of real estate on the front grille.

Fan - pretty sure its faulty, seems to spin four or five full rotations when turning the engine off. Is that conclusive?

Leaks - cannot find any sign of coolant drips on the driveway or leaks during overheating. Would a pressure test tell me anything useful?

Not knowing which one is to blame and given that testing it with the trailer is high risk I don't know if I should remove the head first and work back through that list or hope some of those cheaper fixes will be enough on their own. Thanks for any help.

[Google]

[Simon_W]

Generally when these engines overheat, the head cracks. From the symptoms you've described, I'd be surprised if it hasn't gone.

If this was my vehicle and it was a 'keeper', I would:

1. Replace the head and head gasket

2. Replace the water pump, thermostat, and rad cap

3. Fit new alternator belts (and air con whilst you're there)

4. Flush the radiator and engine block. Check that the rad is clear by filling it with hot water and feeling the temperature across it. If you have an IR temp gun, use that. Refill with the approprate glycol-based coolant. I use Comma Xtream G48.

5. Check that the viscous fan is locking up at temperature (you could probably use a hairdryer/heat gun to do this). These units can be refilled with silicon oil if they aren't working properly.

Whilst you're there, change the oil, oil filter and fuel filter. Then you know that everything is A-OK.

If you haven't got an aftermarket temp gauge, get one. The standard temp gauges are notoriously slow to react. By the time they show hot, it's too late.

I doubt if the front fog lights are the cause of the problem. In really severe conditions you might be better off without them, but not in the UK.

[NDZ]

Thanks Simon I appreciate the input here. Found a local cylinder head workshop that will test it for me and been making a list of new parts, the alt belts were replaced less than a year ago, rad cap just a month ago the rest I will do as advised.

Flushed the radiator and engine it was totally clean not a bit of crud or oil in the coolant. I removed the thermostat (no help from the Haynes manual on a 2.8) and will drain it again shortly after a run up to temp. I was planning to pull the heater pipes but did not like how much resistance they were offering, possibly not been removed in 20 years but the heater has always worked perfectly. I've yet to test the radiator with hot water but my hunch is there are no blockages or issues with the pipes.

As for temp gauges - on a completely different project I made a thermostat from a STC 1000 with the sensor drilled into aluminium block and thermal glued so I'm familiar with that kit. I noticed Pete had done similar but seemed to suggest a standard aftermarket water gauge was just as reliable - is there a preference for any particular type of temp gauge here?

Likewise are there any specs on the viscous refill oil?

Just a thought I was having while tinkering and reading the forum - I've absolutely no use for the aircon, it has never worked and I didn't re-fit the compressor belt last service. The vehicle is only for towing a trailer and I liked the sound of using the electric fan for additional cooling but looking at the grille on a 2.8 has anyone simply removed the entire AC condenser and other bits? While I was there I got confused again with the Haynes manual, what is the black radiator left of the electric fan? Haynes seems to describe it as an oil cooler then suggests the 2.8 doesn't actually have this part but has the oval cooler with fins.

[Simon_W]

I think there are better manuals than Haynes. I'll sent you a private message with links to my Dropbox so you can download the factory workshop manuals.  

It's worth flushing out the heater matrices if you can. If the hoses refuse to come off, maybe best to leave as is.  If it ain't broke......

As for a temp gauge, you get what you pay for. I bought a cheap analogue one and it read about 20C too high, thus giving me a rather worrying test drive. I put a potentiometer in the circuit so that I could trim it accurately using an IR thermometer. These are a great investment at about £5 from Ebay.  Do a search on here and you'll find info on what others have fitted.  If I was doing the job again I'd fit either a Durite or VDO.

10,000 CST silicone oil for the viscous fan.  50ml, I think.

I recall that others have removed the aircon condensor and used the fan for additional cooling. It really shouldn't be needed though.  The cooler that you are referring to is for auto transmission fluid. There's both a separate cooler and one integrated with the main radiator.

[NDZ]

Parts on the way, regarding the new temp gauge I've found plenty of posts here but still not sure if folk are replacing the original sender (doesn't that also supply the ECU?) or cutting into the rad pipes with an adaptor and running both old and new.

[hutchy]

cutting the hose and fitting an adaptor is the way it,s done the adaptor size is 35mm diameter

[peteinchad]

[NDZ]

Fabulous, thanks for the help. I've been checking out some options in case I need a new head, found a Delica breakers nearby and presume the 4M40 head is the same in Delica and Paj, might be worth the gamble to get one and have it tested. Would anybody risk a chinese head with a 42mm radiator and new temp gauge?

[vijay]

I fitted an Ebay Chinese head a few months ago and it runs perfectly. It's early days but I'm more than happy with it.

[NDZ]

Some progress, got the radiator out and was surprised its only just over 25mm, is this factory stock? New water pump and thermostat about to go in, tested the old thermostat and in a pan and it seemed within limits and the old pump wasn't showing any obvious problems. Removed the viscous fan for servicing it had maybe 30ml of oil in there, I have 80ml 10,000 CST to replace it with and also noticed this little black part when separating the body. I presume its a kind of woodruff key that fits back in the slot but didn't really see where it came from.

Bimetallic strip seems in good order, blew the holes out with an airline and the oil turned to snotty custard, very odd stuff. I'll probably refill it generously as it's currently an overheating two vehicle and I'd rather the fan locked up than any other option.

While I was there I removed the AC condenser, it has aged at twice the rate of everything else nearby, the fins turned to powder on touch and the half of the mounting screws broke on removal. Not sorry to see that mess go and hot tested the AC fan for extra cooling it works just fine. The previous owner had fitted a front fog switch on the dash but the fog connectors are a different type to the lamps and I've yet to really need them so I was hoping to hijack the fog switch for an AC fan relay but it doesn't seem to provide power to the front. The switch does light up and is clearly part of a lighting circuit but what I presume to be the front fog connectors don't get any power.

The fog connectors poke out of the grille as 2x GRN/RED and BLK that seem to break out of the harness along with the horn wires. The dash switch has black wires for all terminals that disappear inwards before I can locate any connections. I've had the multimeter on the front connectors and there's nothing, unless perhaps it needs the engine running (not possible right now). Then I tried to locate the horn wire in both Haynes and Mitsi manuals, no luck so far apart from a fuse ID does anyone else have the same connectors at the front?

[NDZ]

pics

[hutchy]

the little black bit fits into the slot that it is next to in your pic it,s not a woodroof key but some sort of scarper that pushes the oil in the coupling...i have filled 3 of these over the years but found they do not last long and ended up buying new ones even though they are expensive,blue print seem to be the better quality for aftermarket even though i did have one that was a bit dodgy as it was not balanced right so ended up with vibration as a result..

[peteinchad]

I bought one off eBay from Poland for £45 and it was rubbish so I got a Blueprint one and it has worked fine for three years up to now.

[hutchy]

well i fitted my bargain one from eblag the other day can,t beet a genuine new part for a knock down price,just need to give it a good run out to see how it goes

[NDZ]

Got the head off. Gasket is rotten, there's bits of rust and gunk in the ports and looks like heck of a clean up. I'm only half sure I even want to clean it and get it tested compared to just ordering a new head and gasket. My guess is that anything could have been happening with a gasket in that state as it has delaminated (or plain fell to bits) to the point where I'm not even looking for cracks as everywhere on the surface is pretty much compromised. I am curious about the head though just for purposes of troubleshooting the overheating issue, I'll probably clean it up to see if anything is visible at least.

My new concern is that head bolt #1 (the shorter pair at the front) was sat rotating in its hole and I presume the threads are stripped in the block. Looking at the head I'm thinking it doesn't have anywhere near the pressure to cope with that the other bolts do but still not good, Any ideas about re-tapping or such?