GU 4.2 getting hot has anyone tried this as a possible fix

Submitted: Monday, Jan 07, 2008 at 11:10
ThreadID: 53199 Views:6490 Replies:7 FollowUps:9
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Our GU 4.2 Turbo suffered the same getting hot issue towing our newly acquired second hand off-road caravan at xmas , was fine temp wise according to the standard temp gauge, except when we started to climb the Binjour plateau, it's a sneaky climb for a couple of minutes and finishes with a steep climb at the end, it was 38 degrees in the cab so probably 40 + off the black top.
The patrol has a 3" exhaust , Garrett B/B turbo & liquid to air intercooler with the intercooler radatior front mounted. I intend to fit a water temp gauge & EGT gauge so I know exactly what is happening.
Having read on this forum and others what has been done to try and solve the problem with (in most if not all cases that I have read about) having only achieved a minimal improvement if at all, I was wondering if anyone has heard of an after market water pump (replaces the existing one) that is available that is supposed to increase water flow and therefore the motor runs cooler. Is this wishful thinking, has anyone tried this , don't want to spend $$$ for a nil or minor improvement. Have also been told that and electric water pump can be fitted which will fix the problem, any comment / feedback would be greatly appreciated.
Thanks in advance.

Regards Guy
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Reply By: Member - Roachie (SA) - Monday, Jan 07, 2008 at 11:42

Monday, Jan 07, 2008 at 11:42
G'day Guy,

I know where you're coming from mate and I sympathise with you. If you've looked through the archives you've no doubt seen plenty of commentary from me about this issue over the past 4 years or so.

I contemplated fitting a Davies Craig electric water pump, but in the end decided against it as I couldn't see an easy way of plumbing it in without it "hanging" off the hoses either side of it and felt that it might end up causing a failure of the lower hose/s.

There was a bloke who came onto one the many threads about this and cryptically described that all we needed to do was replace the OE water pump with one that he (or was it his mate) had designed etc....but he didn't elaborate and then disappeared.

In the end, it seemed to me that, after trying heaps of fixes, it was all a waste of time. A few blokes pointed out the probable cause for the TD42 to get over-warm (note, I refuse to use the term "overheat" as that tends to conjour-up pictures of the truck stranded on the side of the road with steam coming from under the bonnet etc.....that NEVER happened to me). The main thing to remember is that these are a low-tech motor which wasn't designed to be turbo-charged. The water galleries are (apparently) quite small when you take into account the mass of the block. As such, there is insufficient capacity for any amount of coolant flow to absorb the heat of the block and transfer it to the radiator. If you could, in theory, fit a water pump that flowed 10 times the amount of water that the current one does, you're still not going to change anything as the water wouldn't have time to "collect" the heat on it's way through the engine. What it needs (which is not physically possible as far as I know), is to have a grinding implement (similar to those electric eels that plumbers use to clear blocked drains), that you could feed in through the motor and make the water galleries physically bigger....another analogy is those balloon gizmos (stents?) that they use in caronary surgery to open out blocked vessels around the heart. As I say, it's not possible, but I think that's the only way you could fix it.

You can rest easy to a certain extent that you have a very tough old motor and even when it's operating at over 100oC it will happily do that all day long...... where it's breaking point is, I was never able to ascertain.

AnswerID: 280244

Follow Up By: Member - Guy 59 (QLD) - Monday, Jan 07, 2008 at 13:07

Monday, Jan 07, 2008 at 13:07
Thanks Roachie,
I have read some of your threads re the issue and was using your experience as a guide so I don't get conned into doing something that won't help,it seems you did nearly everything possible without any real success and it appears that there really isn't a "fix" as such, so a couple of gauges and monitor what is happening would be the wisest and probably the cheapest option, I had a radatior guy tell me that if you could double the volume of water circulating through the motor you would only decrease the temp by a maximum of 8% so in this instance probably 8 or 9 degrees ....... uhmm not worth it I don't think.

Thanks for your input Roachie, and watch the right boot on the exaggerator pedal, don't want to be making any more "donations"

FollowupID: 544470

Follow Up By: Member - DAZA (QLD) - Monday, Jan 07, 2008 at 14:36

Monday, Jan 07, 2008 at 14:36
Hi All
I was wondering if thermo fans would help?

FollowupID: 544481

Follow Up By: Member - Dunworkin (WA) - Monday, Jan 07, 2008 at 15:18

Monday, Jan 07, 2008 at 15:18
Hi Roachie, we have a 4.2GU, we bought it 2nd hand when it had 55.000 Ks on the clock (we have upt it since then ha ha ha)
we have never had any problem (up to this point in time) with temp. the gauge goes up mid way and that is where it stops, we have to climb a hill with our 18ft caravan to get home, we have pulled it up Bindoon Hill over here and the temp just rises a little but we have never had any problem with it. Have checked the motor after a big climb (thinking it could be the temp gauge) but the motor is fine. My question, given all the problems that others are having, is what could be different with ours? I have followed these threads for a couple of years now and it does have me puzzled. If I could find out why ours doesn't get hot we could solve the problem for others.



Simba, our much missed baby.

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FollowupID: 544487

Follow Up By: Member - 120scruiser (NSW) - Monday, Jan 07, 2008 at 15:54

Monday, Jan 07, 2008 at 15:54
Hi Dunworkin.
I have a customer with a 2001 4.2 and he tows a 22 foot van and has neve had any dramas with over heating. Its got me beat what the problem is.

I do run GMH coolant in his at 30+%
You wouldn't think the brand of coolant would make a difference would you?

FollowupID: 544496

Follow Up By: Member - Roachie (SA) - Monday, Jan 07, 2008 at 16:34

Monday, Jan 07, 2008 at 16:34
G'day Dunworkin,

Part of the issue is the sensitivity of the original Nissan gauges (and all other standard temp gauges as well I believe).

You see, the real temp of the coolant isn't relayed to you via the normal gauge. These gauges are designed to give you some comfort when travelling. It's not until/unless you fit a "proper" gauge (like VDO or Autometer) that you start to get a feel for what is REALLY happening inside your motor.

At the moment you look at your temp gauge and say to yourself... "this is great, my truck's water temp never varies, or if so, only by a few degrees"..... sorry, but this is WRONG.

If you fitted another proper gauge in addition to the Nissan gauge, you would be surprised by just how much your coolant temp varies by. It will be about 50oC when the Nissan's gauge reaches the "normal" position (usually this is just shy of half way). Now, you can drive it hard and watch the proper gauge will go anywhere between 50oC and about 105oC, before the lazy ol' Nissan gauge will move away from the normal position. From there up it's only a matter of about 13oC between the Nissan gauge reading normal and being just outside the HOT zone (around 118oC).

So, as you can see, when you say the Nissan gauge in your Patrol only just goes past half way, you are probably getting up around 110oC REAL water temp. Now, that is not boiling because it's under pressure and as long as your cooling system is in good condition, you have nothing to worry about.


FollowupID: 544499

Follow Up By: Member - Dunworkin (WA) - Monday, Jan 07, 2008 at 23:24

Monday, Jan 07, 2008 at 23:24
Thanks for that info Roachie, much appreciated. I was of the opinion that these people were having to stop because the vehicle was really overheated, like boiling (silly me) I might try and talk hubby into getting a temp gauge put on (that shouldn't be too hard to do, another gadget for him) although maybe not, what the eye doesn't see etc etc lol.

Hi 120scruiser, thanks for your input, we only use coolant but I'm not sure which one our mechanic uses but we have confidence in what he uses, he has proven himself many times over.

Thanks again all,



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Follow Up By: Member - Jerry C (WA) - Tuesday, Jan 08, 2008 at 00:43

Tuesday, Jan 08, 2008 at 00:43
Hi All,

With all the research that has been done to identify these heating problems, has anyone ever measured the temperature drop of the coolant across the radiator core? top hose to bottom hose. My own experience some years ago proved to me that if you didn't have at least 7c temperature drop then I was wasting time and money.

Cheers, Jerry.
FollowupID: 544620

Reply By: Member - Coyote (QLD) - Monday, Jan 07, 2008 at 12:35

Monday, Jan 07, 2008 at 12:35
Another problem that seems to be related to the "oilers" that I've been told is that apparently the GU's radiator is considere dot be fairly 'fine' in that it blocks up quite easily, a small amount of debris easily gets stuck in say the middle of the daiator and next thing you know you arenow running with what is effectivly half a radiator. I found that when I had my 2.8 that after repeated overheating, after removing the daitaor, opening it, cleaning it and the refitting it, I was able to tow my trailer etc at 100km/hr, climb hills etc and the temp guage never moved again..
having said that I'm not talking about towing a caravan or boat. I have a 05 4.2 now and although "touch wood" never "excessivly heated" (thanks roachie - not 'over heated') but I know that it will probably happen in the near futuere and the first thing I willbe doing is flushing the radiator nd if that doesn't help removing it and opening it and cleaning it right out. Good luck.
AnswerID: 280251

Reply By: Peter 2 - Monday, Jan 07, 2008 at 12:41

Monday, Jan 07, 2008 at 12:41
I don't know whether anyone has tried this but straight water actually conducts heat better than coolant, in fact the more coolant you have in the cooling system the poorer the heat transfer.
Has anyone tried dropping the coolant into a bucket and then replaced it with clean fresh water and then gone for a drive to see if the engine gets warm or indeed if there is an improvement.
If there is an improvement then replace the coolant but don't go over 30% coolant, use clean water for the rest. Also put a bottle of Water Wetter into the system as well as it lowers the surface tension of the coolant/water mix and gives better heat conductivity.
Although water wetter is available in the grey colour for diesels the tech bods told me that it is mainly for the Euro diesels with the metal mix in the Volvo blocks and we can use the red petrol mix in most 4wd diesels with no problems.
AnswerID: 280253

Follow Up By: Member - Matt (Perth-WA) - Monday, Jan 07, 2008 at 12:49

Monday, Jan 07, 2008 at 12:49

Im not going to comment on the heat transfer ability of water over coolant but the other benifits of coolant must outweigh that. The higher boiling point will allow the coolant to absorb more heat than water before boiling plus it does lower the surface tension and prevent cavitation on the wet liner walls.

Anti corrosive and anti gelling anti freeze...

I remember reading about vehicle manufaturing and testing using 100% glycol solutions in some applications to prevent over heating. Will have a search and see if I can find the exact reference.

I will stay with good quality coolant and change it every few years.

FollowupID: 544466

Reply By: RedGibber - Monday, Jan 07, 2008 at 14:14

Monday, Jan 07, 2008 at 14:14
I too have a TD42T (late '02 model) and have suffered the "overly warm" syndrome on the odd occasion in the past.

The solution - if I could call it that - for mine was a little unexpected, but seems reasonably effective.

After fitting the 3" Beaudesert exhaust I had the OEM turbo modified (bigger turbine) and the fuel pump timed WITHOUT increasing fuel. Boost was unchanged at around 9.5psi. The performance after these mods was quite adequate without being "outstanding" and I was pretty satisfied nonetheless. One thing I did notice tho' during our recent trip up thru the Centre and back via the Kimberley/Pilbara towing our Sunland van, was that the EGT would continue to climb above 500 degrees C on hills etc., requiring a bit of accelerator adjustment to keep EGT temps at around 500, no more.

So when we got back from our trip, I decided to up the boost to around 11.5psi (I have a manual boost controller fitted). The test came last week when we drove up to Green Head towing our 5.3m plate alloy boat in 40+ degree temps. The EGT maxed out at ~500 degrees, and even with my foot flat to the boards it did not increase!

I believe the reason for this is that at high boost the air to fuel ratio is higher i.e. more air, therefore combustion/exhaust temps. are a little cooler. Can someone confirm this view pls??

Anyway, it's made me feel a little more comfortable even tho' I'm still monitoring the EGTs closely when towing!

Red (Andy)
AnswerID: 280267

Follow Up By: Member - Oldplodder (QLD) - Tuesday, Jan 08, 2008 at 09:47

Tuesday, Jan 08, 2008 at 09:47
Noticed the same thing on my EGT in the pajero with the older 2.8.
Found that the EGT was a lot lower (about 50 to 100 deg) at 3000rpm than 2000rpm at full throttle climbing a hill. Basically one gear lower, but the same speed.
I have upped the boost (11 to 15 psi) and turned the fuel back half a turn so I don't get much over 700 deg C max before the turbo. Still the same max power, if not a little more.
As you say, I feel I am getting more air into the system, and cooler temps. The Pajeros have an overfuel boost function on the fuel pump and they do blow a fair bit of soot on full throttle on stock settings.
FollowupID: 544656

Reply By: Member - beachbum - Monday, Jan 07, 2008 at 16:01

Monday, Jan 07, 2008 at 16:01
Guy I also have the problem with my 4.2TDI Cab Chassis and have a Motson 3 inch exhaust and the pump retimed and tweaked and this gave far better performance, had the radiator changed to a Natrad copper cored unit, have replaced the aircon condenser (due to damage in the Simpson), used the recommended waterwetter and replaced the thermistat and should have saved my money. I would not use plain water as someone suggested as there is a fair bit of Alloy in the motor. I doubt that fitting other gauges will do anything for you other than to increase your anxiety. I just watch the temp gauge do it's thing now and trust that it will quickly return to normal when I have crested the rise/hill that caused the rise in temp. While I was towing a 16 foot pop top van and went around the block with it, there was never a problem other than climbing Ben Lomond north of Tamworth and I have also driven the vehicle pretty hard off
road at times again with no problems but, with our current 21 foot full van it indicates it is getting a bit warm fairly often. I live in central Qld so most of the year it is warm as well but no longer worry about the rise in Temp and as Roachie has said, they are a very tough old motor. Just my thoughts on the matter and good luck with whatever you decide to do.
AnswerID: 280287

Reply By: Old Johno [NSW] - Monday, Jan 07, 2008 at 17:54

Monday, Jan 07, 2008 at 17:54
We have a 2004 4.2 GU Intercooled turbo. Has 3" exhaust & the turbo has been upgraded by MTQ.
At 70,000km's started having heating problems when towing caravan up long gradual hills. Took it to Traction 4 North Sydney where they had the radiator rodded & cleaned out with no further problems. They state that the newer models have an Aluminium type core and they are prone to this problem at approx 70,000k's
AnswerID: 280306

Reply By: Member - Luke (SA) - Monday, Jan 07, 2008 at 23:29

Monday, Jan 07, 2008 at 23:29
My GU 4.2 only gets warmer than the normal temp when the ambient temp reaches around 40oc.

Last week when driving home from Robe the ambient temp reached 40 and the 4.2 temp started climbing. This only happened when I left Palmer going up those steep hills. The first time the temp went up SWMBO was driving and let me know what it was doing. I let it go till it got to the line before the Hot and told her to pull over. I got out of the Patrol, lifted the bonnet and the water inside the reservoir was boiling away. Let her idle for about 5 minutes till the temp went down to just over half then was on my way again.

Due to the length of the hills I had to do this a couple of times, the last time I pulled into a parking bay, parked under a tree for 20 minutes with the engine off but ignition still on keeping the thermo fan running. In this time the ambient temp had dropped from 40 to 35oc and the 4.2's temp went to below half where it sits normally.

From then on the temp didn't rise but we also didn't endure the amount of hills either.

Both viechle and camper were packed for the weekend we had just had so the Nissan wasn't just idling thru town if you know what I mean.

Cheers Luke
AnswerID: 280401

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