overheating under load NH 2.5 DIESEL

[IAN SMITH]

1991 NH 2.5 diesel still has temperature rise when climbing hills but goes back on the flat. Engine only 125000 kms, has had new turbo,new 3 core radiator,new thermostat ,new water pump,rebuilt diesel fuel pump at cost of $2800, Viscous fan working.Did have a custom made fan cowling but mechanics took off as they said it was restricting air flow to radiator so now now fan shroud which could be the problem .Cannot locate a replacement fan shroud ,Need help to locate one.

[wazza87]

Overheating

Hey mate,
Looks like you have done alot of work there. Can I ask what thermostat you used? When I rebuilt my front end I found an 82C thermostat in it with a hole drilled in it. You need a 77C one because the t-stat is located BEFORE the water pump. This means the water coming out of the head is really hot but it is cooled by the rad before it reaches the t-stat. So, you need to account for that drop in temp somehow which is where the lower rated t-stat comes in.

My gauge usually sits around 1/4 off the cooler end. When loaded up long hills with high egt's it will come up to nearly half way. I prefer to see the temp gauge move rather than always be at the same spot so I have a good idea of how hot it really is getting in there, and can avoid excessive heat by backing off.

So without talking about mechanical reasons you are overheating, how about, is the temp sender working correctly? I have recently needed to replace mine. You can check it quite easy using an ohm meter/mutimeter and a pot of boiling water. I can upload a picture from my manual of the procedure if you would like.

Waz

[geopaj]

What temp (degrees) does it normally run at, and what is it going up to when climbing hills?

For comparison, mine sits about 88c but when seriously working will go up to high 90's c

[dhula]

Assuming this thread and the one in Mechanical are the same person and car.
Spend $50-$60 more and put in a aftermarket gauge. They usually come with a sender included but not sure what thread is on the 2.5TD so check and make sure you get the right one or the right adapter to suit.

A couple of extra things I haven't seen in either thread yet
Fan clutch - replace it, not check it or refill it, replace it. It should roar like a lion at cold start up and take about 30 secs - 1 minute to quiet down give or take. Defo easier to hear when reving at about 2-3k. If it doesn't behave like that it's likely that it's not working properly.
Tyre pressures - check them and make sure they are OK.
Brakes - Make sure they are not dragging or sticking on, handbrake included
Oils (all of them) - Make sure they are at the correct levels, not too high and not too low
If it has a SS4 Tcase, put it in 2wd

[IAN SMITH]

Assuming this thread and the one in Mechanical are the same person and car.
Spend $50-$60 more and put in a aftermarket gauge. They usually come with a sender included but not sure what thread is on the 2.5TD so check and make sure you get the right one or the right adapter to suit.

A couple of extra things I haven't seen in either thread yet
Fan clutch - replace it, not check it or refill it, replace it. It should roar like a lion at cold start up and take about 30 secs - 1 minute to quiet down give or take. Defo easier to hear when reving at about 2-3k. If it doesn't behave like that it's likely that it's not working properly.
Tyre pressures - check them and make sure they are OK.
Brakes - Make sure they are not dragging or sticking on, handbrake included
Oils (all of them) - Make sure they are at the correct levels, not too high and not too low
If it has a SS4 Tcase, put it in 2wd

Thanks 3 Mechanics assure me the fan clutch is working and it does roar on start up on cold.Temp gauge sensor was replaced.Temp gauge is very responsive to slight loads when going up hill .Especially once revs are over 3200, At 100 kmh no problems on the flat.Have just taken off the LED 22 inch light bar which was mounted in front of the radiator grille. Will see if any difference.

[dhula]

No offense to your mechanics but I've been caught with fan hubs before. Emptied, cleaned and refilled one and while it felt and sounded like it was working properly, when push came to shove the car overheated going up hills, was perfectly fine on the flat though. Changed the fan hub and it didn't overheat anymore. It turned out to be the thermo strip was not doing exactly what it should have been
The cost of a new one considering the amount you've paid out so far is nothing (seen them for ~$100).
Another couple of thoughts (not sure if they have been mentioned yet so sorry if I've doubled up)
Is the fan on the right way and is it working OK. I've seen plastic fans go super soft and flatten out when spinning fast
What % is your coolant, eg 50%/50%, 33%/66%. I've seen some engines run slightly hotter on the gauge when using 50/50 yet on 33/66 it will run fine.

[green troll]

I know how frustrating this can be. Had it on a previous 4by.
Things I did in one go
Fan clutch and new blade-correct orientation

New water pump

New radiator cap

New thermostat

At least new top/bottom hoses. Sometimes they can close up

New radiator. Or at least a rod and clean

Can't tell you what it was as I just wanted it fixed. I also replaced all hoses and flushed block and correct ratio fluid.

Doing it all yourself you can get away with it rather cheaply. Just try one thing at a time.

Good luck mate