NM overheating on beach

[nicco]

Hi guys,

First post on the paj forums

I've got a petrol nm automatic. I've recently started trying some beach driving and have noticed the temperature is going uncomfortably high. I'm hoping to get some suggestions on either my technique or mechanical items to stop it.

First time tyre pressure was at 18 psi driving in low range in drive on a hot day. Only made it about 200m and the two was already starting to creep up.

Second time dropped tyre pressure to 13 psi, kept it in high range and in second, kept the speed up a bit higher as well so the car wasn't working as hard. This time I got about a km down the beach then the temp started to creep again.

About 6 months ago I fitted a new radiator, full flush, new thermostat, new coolant and a couple of hoses and what not. Water pump was replaced about 50000 km ago when the timing belt was done. The serpentine belt is in good condition and doesn't show any signs of slipping on the water pump.

Even on really hot days on the road the temperature doesn't budge, only under the extra load of driving on the beach.

As you can see I've tried to check everything I can think of. I'd really appreciate any suggestions at this stage. I'd love to do more beach driving but the last thing I want is to cook the motor!

Thanks in advance,
Nic

[green monster]

Might be worth checking your fan clutch too?,

[Phil]

First thing is to do a search on the NM temp gauge problems.

Tyre pressure seems about right depending on how fine the sand is.
I never had any temp dramas on Fraser for a week but went 200m down Stockton and had to low the pressure a bit, while its all sand there is different sand.

[Herman4x4]

Gday. The coolant hasn't gelled in the radiator? This can happen when changing coolant and the old coolant hasn't been fully flushed out.
Cheers,
Andrew.

[Bundyk]

Might be worth checking your fan clutch too?,

x2. Seems about the only thing left to be checked. That or the temp sender

First thing is to do a search on the NM temp gauge problems.

Tyre pressure seems about right depending on how fine the sand is.
I never had any temp dramas on Fraser for a week but went 200m down Stockton and had to low the pressure a bit, while its all sand there is different sand.

Temp gauge issue will show as erratic temperatures ie needle goes to hot not long after starting the car. The fact that the temp gause only rises under load says its probably not the gauge

Gday. The coolant hasn't gelled in the radiator? This can happen when changing coolant and the old coolant hasn't been fully flushed out.
Cheers,
Andrew.

New radiator and coolant fitted not long ago

As Andrew has said, check the viscous coupling on the fan. It could be on its way and need replacing.

[Phil]

How high is the gauge going, if its only to say the 3/4 mark it could just be tyre and gear selection issues.

[my.paj]

Check auto and its cooling system (if auto).
Rick

[nicco]

Thanks for all the comments so quickly.

I'm fairly sure it's a real problem not just a dud gauge; the first time I went beach driving you could smell the warm engine and it even started to detonate a little bit; that was when I promptly stopped and let it cool back down. Took about 20 minutes stuck in the main entrance to the beach.

Phil: first time the gauge went right towards the top. Second time it probably crept to about 3/4. It's not beyond the realms of possibility that I'm doing something wrong in the way I'm driving. I was aiming to keep it at about 30km/hr the second time and in 2nd gear in high range, so about 2000 rpm.

Herman: I don't think so, the coolant still looks good at the moment and the radiator is new with the full flush.

MyPaj: What sort of things would I need to be looking for with the auto? Do the Pajs run a separate oil cooler for the trans or is it built into the radiator?

BundyK and GreenMonster: That's a good suggestion. Is there any way to test the operation of the fan or is it just something I need to replace and then test? The blades are physically in good condition.

[Easykill1978]

errr those motors can handel heaps.. many have takent them thru the simpson desert and all ok..

easyk

[IronMan]

Are you sure you need low range? I have an NP DiD manual and haven't had the need for low range on Stockton or even getting off the well chewed up Samurai. Nor have I had issues with overheating.

(Disclaimer: I haven't seen your beach, you very well may be right!)

[dolphin]

i have the NM auto. only ever needed 4 x 4 high for any beach stuff.
if your cooling system has the following replaced i can only leave you with 2 things to consider fixing.
thermostat.
radiator.
radiator cap.
waterpump.
correct engine timing.
the fan may not be working at low engine rpms or the coolant system has an air gap in the engine which needs to be bleed out.
what else could it really be. ???

[nicco]

Righto, a bit of an update. After this thread I went and did a bit of reading on viscous fan clutches. It turns out mine wasn't locking up properly (I think, they are a little bit unclear as to whether they are working or not).

Went and installed a new clutch and I could really hear it clutching up on start-up and then quieting down, so I'm thinking the new one is working better.

Went for a drive on a Bush track yesterday, about 30 degrees, high range, 1st and 2nd gear at <2000 rpm the whole way, some sand but not very deep, tyres at highway pressure. Started trying to climb some inclines (just long, uphill sections) and the temp started creeping again. This time it got to about 2/3 on the gauge.

I was hoping the new hub would be a silver bullet, but apparently not.

With that in mind, is it just normal for an auto, v6 paj to get a bit warm in these conditions? I didn't get a long enough run to see if it stabilised at that temp or would've kept climbing. I probably won't get to do a proper beach run again for a couple of weeks to really test it.

The other thing I was thinking is that the auto gets very hot; you can feel the heat off it through the trans tunnel next to the foot rest. Is that normal? It's always got that hot for as long as I can remember. I borrowed it off my dad when it was his back in 2004 and noticed the same thing then.

I used to own an EF Falcon auto that used to get very hot when doing high load work like a range road; I converted it to manual and it never got hot again. I'm wondering if it might just be the load of the auto that pushes the cooling system too hard? Maybe a stand alone transmission cooler?

[my.paj]

My NL behaves like this sometimes, I think mine is the auto working very hard and in need of a service, when I was driving up to the top of MT Buffalo I noticed the temp creeping up so pulled up and found 2 problems, the first was the trani cooler was so hot that it burnt my finger on a quick touch, the second is that I could hear a hissing sound around the motor I think it was behind the thermostat housing.
I still have not fixed these problems but to prevent them when I drive up hills I use the gears, I'v never lost coolant, I did move the trani cooler and that made it a bit better the one thing I know I need to do is service the trani.
Just giving you my thoughts on my problem.

[geopaj]

My NL auto (engine is basically the same as your NM) got hot towing my camper trailer in the dunes on a recent forum trip.

Fan viscous clutch has tested fine.

About 5 years ago I had a 3 core radiator made up to replace the standard 2 core radiator.

This is what I am doing to address the current cooling issue-
1. New thermostat.
2. Flush and replace coolant.
3. Having the radiator 'rodded' (both end tanks removed and the core cleaned out). The local radiator shop has quoted $100 to do this but I had to remove the radiator.
3. Clean out outside of the air con core and radiator of mud (each was about 10-20% blocked)
4. Installing a trans cooler. My local auto trans shop has suggested not using the cooler in the radiator (auto trans oil can get to 120c plus when working hard so would be adding to the cooling system stress). I will be running the standard external cooler plus an afetrmarket 20cm x 30cm trans cooler.

As my.paj stated, the auto transmissions get very hot when they are getting worked hard with very little airflow.

[nino]

Ours is diesel with a lot of kms and we have a similar issue on specific types of sand: if I don't air down the pajero digs in and heats up. With low tyre pressure it floats and doesn't heat up.