NP Overheating on Hills when Towing

[netorius77]

I am towing a 1750kg caravan with my '03 Petrol NP Auto (132,000 km). On a couple of occasions, I have found that the car begins to overheat on an incline or after a long stretch in soft sand (beach, but not towing).

I read this thread where a lot of comments on a similar issue were made: http://www2.pajeroclub.com.au/forum/...ad.php?t=10256

The most recent issue, the day was fairly warm (32°C) and I had the a/c on which I switched off pretty fast when the temp headed north. and dropped into 3rd gear and held it there at about 2900 RPM for the climb. I generally keep the car in 4th for the trip and find that it seems to keep it cooler - no scientific evidence though... but even if it is not overheating I find it pulls and holds speed better in 4th.

The rest of the trip was reasonable as long as I kept the a/c off on the hills.

My feeling is that the radiator keeps both engine and AT cool, so to maximise engine life, it doesn't pay to run it hot. Looking at this site (previously recommended in a thread) http://www.nationwideautoparts.com.a...ERO%20RADIATOR, it seems that one can purchase a brand new HD radiator for $621. What does it cost to rod out a radiator at the agents - pretty close to that with their costs and then filling with coolant etc. I would think. Is it a big job to change out as a DIY job, and just be done buying a new one? Could the thermostat "stick" and not fully open?

Appreciate comments and suggestions as I do not want to fork out unnecessarily.

[joe2006]

I personally would not be changing my radiator unless I knew that was the problem.

While our Pajero does not run hot, I had a Discovery that would run hot up inclines. It was the viscous fan that was not operating properly. Changing the radiator would not have solved the problem. It could possibly be something as simple as a faulty thermostat, timing or something?

Good luck.
P.S I just read some of the posts in the link that you provided http://www2.pajeroclub.com.au/forum/...ad.php?t=10256 It seems to cover pretty much everything
:-)

[gaz1]

as mentioned in that earlier thread, your problem is likely to have been caused by gelled coolant - happens when incompatible coolants are mixed. You can't rely on MMA dealers to use MMA coolant, they will often opt for whatever is cheapest, then you have mixed coolant in the system. I had a new radiator fitted under warranty early in the life of my Pajero and it was OK for a while then the problem reappeared when towing my 2.3t van - radiator again blocked with gelled coolant. I can only assume that when the new one was fitted they didn't properly flush all the old coolant from the engine block, heater, hoses & pipes etc.
So a few years ago I fitted one of those radiators you have provided the link to and things seem OK so far (also put in a new fan clutch and thermostat, so one of those may also have been a problem). When I fitted the radiator, I flushed the whole system three times with clean water until it drained clear, no trace of green. Undoing the hoses that are located under the driver floor got lots of trapped coolant out and made the process quicker.
The physical fitting of the radiator was simple, pretty much a lift out, drop in process. I had to make some very minor adjustments to the fan shroud so it would fit the thicker radiator. Now I know what coolant is in my car's system and I don't let anyone else get near it.
Gaz

[Goodsy]

Drain coolant. Flush well! There as products out there that will clean your cooling system but not fix a stuffed radiator. Also for the price change the thermostat and when completly flushed run on water for a few days then drain again and fill with coolant.

If all else fails like it did in my Hilux. Viscous coupling. Then Radiator. Not cheap but it fixed my problem.

[netorius77]

Overheating - Plan of Attack

Thanks for the responses. It seems that the four likely issues would be in order of attack (this is on the basis that I am not actually leaking or losing coolant):
1. Gelled radiator - flush and fill with fresh decent coolant
2. Thermostat - not sure how to check, but maybe just replace anyway?
3. Check fan clutch - any advice on how to check this (besides the obvious - overheat the engine and see if it comes on!)
4. Replace radiator when tubes are blocked. (any ideas what it costs to "rod" the radiator instead of replacing?)

Should I be able to tow with the a/c on if the cooling system is OK, or is it pretty normal practice to manage the engine temperature by switching it on and off manually as the engine temperature rises? I guess the answer is obvious - with a decent cooling system you shouldn't but if the temperature does rise, manage it by switching off the a/c and then if still not cooling switch on the interior heater and full fan to try and assist in dissipating some heat (a little uncomfortable, but an emergency aid).

[joe2006]

My understanding is that a viscous fan will still rotate but will slip until it reaches a pre-determined temperature and then when that temperature is reached, it will effectively lock & spin at a 1:1 ratio with the pulley. At that time & with enough rpm, the fan will roar due to the air being pulled through the radiator.

I covered the front of my radiator & to precipitate overheating and ran the motor at around 2500rpm (from memory) & waited for the roar which of course did not happen.

As I said, that was a Discovery (V8) so others who are more enlightened may provide some advice as to how it is best for you to test the viscous coupling.

Finally I have towed a significantly heavier van with our Pajero in 40+ degree temperatures & never needed to consider turning the AC off.

[t0ne]

Thanks for the responses. It seems that the four likely issues would be in order of attack (this is on the basis that I am not actually leaking or losing coolant):
1. Gelled radiator - flush and fill with fresh decent coolant
2. Thermostat - not sure how to check, but maybe just replace anyway?
3. Check fan clutch - any advice on how to check this (besides the obvious - overheat the engine and see if it comes on!)
4. Replace radiator when tubes are blocked. (any ideas what it costs to "rod" the radiator instead of replacing?)

Should I be able to tow with the a/c on if the cooling system is OK, or is it pretty normal practice to manage the engine temperature by switching it on and off manually as the engine temperature rises? I guess the answer is obvious - with a decent cooling system you shouldn't but if the temperature does rise, manage it by switching off the a/c and then if still not cooling switch on the interior heater and full fan to try and assist in dissipating some heat (a little uncomfortable, but an emergency aid).

I just done my radiator, same problem as you overheating going up hills when towing my van...

I replaced my thermostat and flushed and had the radiator rodded...

Fixed my problem now runs perfect.

about $70 for thermostat from memory, and its about 150 to have radiator done(plus labour of removing and refitting and coolant)..

glad i did now i have peace of mind

[SWB ANDY]

another thing to consider as your paj is an auto, do you have a secondary radiator fitted for the autobox, i had a similar experience in the uk towing a 24ft twin axle caravan up the mountains of north wales, the car overheated going up one such mountain road, when i pulled over there was water spewing from the pressure cap on the expansion bottle, let it cool and refilled with water and was expecting the head to have blown, the head was fine, the reason behind the overheating was the autobox as the cooling for the box runs through the main radiator so if the auto is running hot it will heat up the radiator and show as the engine is overheating, most auto boxes need to have a secondary cooler fitted for any major towing work, at around $200 it is a cheap insurance against overheating and eventually a dead auto, i would highly recommend fitting one as it keeps the auto box nice and cool.
just something else to consider

[Handy Andy]

overheating

gidday netorius....re the thermostat

Its relatively easy enough to pull the thermostat out and see exactly what difference it does or doesnt make. follow the bottom radiator hose up to the front of the motor and it will attach to a housing held on to the front of the motor by three (probably)12mm bolts and inside this housing sits the thermostat. remove it and replace the housing, there should be a gasket but cut one out of cardboard if required , there will probably be a bleeder bolt on the housing to allow air out of the coolant system as you refill it and driving will soon tell you " something".
As a rough guide if you place a thermostat in a jar of boiling water it should open, of course different thermostats are set to open at different temps.
Generally with all other relevant stuff being normal if it is in place and not opening your top hose and top tank would normally be very warm as opposed to your bottom hose being cool approx 5 to 10 minutes after start up. If it opens and the water pump is working both hoses will be hot/warm

Andy

[Sixtys Guy]

I had some overheating issues whilst towing as well this past week...... As I was away on holiday I removed the thermostat. Unfortunately I had to butcher it as the 'gasket' is actually rubber and requires the themostat to be in it to seal. I cut the guts out of the thermostat and put it back in. That helped my problem, but didn't solve it completley. I will get the radiator checked this week to see if it is blocked.

[Kingfish]

i recently had the same problem, getting a bit hot when taking on big hills on a long drive home bout 40 degrees. took it to the radiator bloke turns out it had never been properly flushed and was 75% blocked so had to get whole new radiator, thermostat and hoses about $700 id advise taking it in an getting it properly cleaned and rodded. apparently its pretty common for them to block up

[netorius77]

Has anyone replaced a radiator - looks like a pretty straightforward job as a DIY. Only trick maybe how to fill and bleed the new coolant.

Also which coolant is best/recommended.

[shortygq]

Hi - I have an almost new radiator for sale that will slip straight in. It is from an NP turbo diesel so thickness of the core is thicker than your petrol radiator.

[gaz1]

It is a straightforward job, a bit fiddly at times with removing the shroud etc but not difficult. Just bear in mind the need to get all of the old coolant out of the whole system before you put new coolant in.

I've debated with myself about whether this would be most effectively done before removing the old radiator or after putting in the new one. I think probably a good flush after draining the system with the old radiator still in place, then a couple of flushes with the new one in place. Would be interested to hear other peoples' opinions.
Gaz

[netorius77]

Cooling System Workshop Manual

Hi - I have an almost new radiator for sale that will slip straight in. It is from an NP turbo diesel so thickness of the core is thicker than your petrol radiator.

Thanks. Petrol Radiator is 500mm x 700mm, Diesel Radiator is 595mm x 625mm, so Diesel will not be a straight swap.

Looking at online retailer: http://www.nationwideautoparts.com.au/
Standard Radiator is $346.78 incl shipping
Heavy duty Radiator is $706.20 incl shipping (HD core 22mm instead 16mm for SD)

Extract from attached Workshop Manual shows coolant bleeding process.

I can't see why I wouldn't just buy a new SD radiator rather than stuffing around with rodding on a 9 year old radiator. Would an aftermarket one be any less effective that the OEM one? I doubt it.