The Mitsubishi Pajero Owners Club®

Rob1709 · Posted: Wed Dec 12, 2018 17:39 Post subject: Overheating

So been having a overheating issue last few weeks and cannot for life of me get to the bottom of it. Background on truck, had 8 inch lift, 38 in tyres 3 months previously.

So the truck overheats after about 1hr driving, water being lost from overflow in steam.

Truck begins temperature Spike commonly at around 20-30mph, give her some beans and high rpm and temp drops rapidly. This is the same at idle, give it high rpm and temperature drops.

I'm thinking it's a flow/circulation issue but am rapidly running out of ideas.

Parts replaced/addressed

Waterpump replaced
Thermostat replaced and now cut out
New radiator
Coolant flushed out

Any ideas are very welcome at this point!!

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peteinchad · Posted: Wed Dec 12, 2018 17:52 Post subject:

What model and year?

Rob1709 · Posted: Wed Dec 12, 2018 18:04 Post subject:

peteinchad · Posted: Wed Dec 12, 2018 19:58 Post subject:

It maybe the viscous coupling on the fan.

Did you change the diff ratios when you put the 38 in tyres on? - I am thinking that if you are running the standard 2.8 diffs then tyres that large are going to stress the engine as the truck is massively overgeared and that could be the cause of your overheating.

I am also trying to work out how you managed an 8 inch lift !!

Rob1709 · Posted: Wed Dec 12, 2018 20:08 Post subject:

peteinchad · Posted: Wed Dec 12, 2018 20:35 Post subject:

Have you checked for bubbles in the coolant in the radiator neck?

Best to do it on a cold engine - remove the radiator cap and look for any bubbles. If you have bubbles then I would suspect you have the common 2.8 cracked head problem.

Just my thoughts - but I think tyres of that diameter will stress a 2.8 if you haven't changed the diff ratios to lower the gearing back to somewhere near standard. Perhaps it has taken 3 months since doing the mods for the head to fail.

I maybe wrong on that but check for the bubbles in the radiator just to rule it out.

Rob1709 · Posted: Wed Dec 12, 2018 21:02 Post subject:

NDZ · Posted: Wed Dec 12, 2018 23:30 Post subject:

Same as Pete I thought viscous fan was the only remaining culprit - are you sure your electric is up to the task? If the coolant is boiling off in the expansion tank its already at a dangerous level in the system and possibly being forced out rather than expanding normally. It also sounds like the high RPM part is only a fix due to faster circulation. If the head or gasket isn't already damaged I'd be careful how hot you allow it to get as anything past halfway on the dash gauge could end badly.

Did your new rad come with a new 0.9 cap? Worth checking that is working properly and cheap enough to just replace anyway.

Are you monitoring the coolant levels in the rad neck when cold? Tried watching for drips and leaks as she warms up e.t.c.? Heater blowing hot OK?

Are you sure the pump is turning OK at low RPM?

Beyond that all I can think its either a massive blockage, or the gasket/head has gone despite the tests, or the fan is under spec and is only now showing any issues due to another problem elsewhere in the system.

My 2.8 overheated and I found the head gasket had rotted to bits and was boiling off coolant. The head survived for a new skim and I replaced fan oil, thermostat, pump, fitted a 42mm rad, new cap and a digital coolant gauge. What I will say is that the digital gauge helps massively in monitoring anything to do with the whole system, especially compared to the factory dash needle which has a middle tolerance of nearly 30 degC and is mostly useless for troubleshooting.