Heating issue 4.8

Engines and Engine Systems
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AndrewA
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Re: Heating issue 4.8

Post by AndrewA »

Sorry I do believe the previous one was for the Diesel the pressures looked high. I found this under a supplement for the Petrol
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Craig Lord
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Re: Heating issue 4.8

Post by Craig Lord »

Thanks for this Andrew :thumbup: I will re-run the tests because the engine was cold when I did mine and i didnt release the fuel pressure so the results may not be accurate.
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Re: Heating issue 4.8

Post by Craig Lord »

Good evening guys

Time for an update on this issue. I havent had a chance up until last week to try sort it out but I finally managed to do a few things to try and solve the heating issue.

Just to recap the symptom was rapid increase in temperature on the temp guage when exceeding speeds of 100kph in ambient temperatures from 30° and above followed by a rapid decrease in engine temperatures back to normal range as soon as I backed off the throttle and speeds reduced below 100kph. I never pushed it to see just how hot it would actually get but the needle on the temp guage which usually sits at just below half would climb up to 3/4 and was enough to scare me into driving everywhere at 80kph or slower.... not nice at all and I got a serious case of temp guage phobia every time I drove the patrol ....

Ok so what did I do to try resolve it, well here is the first list of attempts:

1) new viscous fan hub from nissan
2) new thermostat from nissan
3) new main engine wiring harness (needed replacement according to the dealer)
4) new radiator cap x2 genuine from Nissan

All this did absolutely nothing and the issues persisted. Things were now getting expensive and Nissan started using words like head gasket which turns the stomach especially when you get the quote for repairs :surprised:

So what followed was multiple tests on the radiator to see if there was combustion gasses present, tests were negative. Compression test came back positive also. Tested the oils in the sump for water but there was none and the engine isint using up fluids. So what next? I couldn't afford to go back to the dealer because the labour charges are actually what kills you so instead I ordered the parts and took over my old mans workshop to do it myself.

I got a new Bosch fuel pump (pula 550 as apposed to the R8000 I was quoted)
A new waterpump from nissan (P750)
New hoses from terrain tamer
A second hand radiator so I could test to see if my new one was a lemon (Thank you Tinus for all your help with this and more)
3 x bottles of silicone oil from toyota so that I could upgrade the viscous fan. I think this cost like P300.

The waterpump is straight forward once you have viscous fan off and the radiator out which is a 2 person job so you dont damage the veins on it. Just make sure not to over torque the bolts when you put it back our you risk stripping the threads in the head. A new gasket is supplied with the pump from nissan.

Apologies I didnt take many pictures of the process of replacing these parts but there are already many helpful threads on the forum regarding these jobs. But I did take a few of the viscous fan...
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Make a mark on both peices of the fan hub so that you can join it back exactly the same after you are done filling it with the new oil. I took a clean rag and dabbed out as much of the original nissan oil as I could get at but I read that it's not necessary to get it all out. I then topped it up with 2 bottles of the toyota oil on the reservoir side which on the 4.8 hub is the half with that attached to the water pump. Put it back together and you are good to go. Literally takes 30 minutes and your fan hub should feel about twice as hard to turn as before. Trust me when you turn your patrol on you will hear and feel the difference in airflow. There is a great video on YouTube to help you through it.

https://youtu.be/mMDqW5u8w-w

Let me tell you guys that fan wants to take off now !! The force of the air its drawing through the radiator after the upgrade actually flexes the cowling at higher revs! Even if you dont have heating issues I really recommend doing this anyway especially if you have a bull bar and winch on as a proactive measure.

I then replaced the fuel pump which is also very easy and nicely explained in other threads on the forum. Also put in the other radiator, new terrain tamer hoses (set asside some time for this if you have a 4.8 and prepare to debone your knuckles :lol: ) and new coolant which was flipping expensive blue stuff :surprised:

Ok so I drove it around Gaborone for a few days but we had unusually cold weather so I wasnt convinced. Today though we drove back to the tuli block, 8 hour drive in 30° heat with a full trailer and roof rack. Did 110-120kph wherever possible and I'm happy to report that the heating issue didnt rear its ugly head the whole way home. I'm not 100% rid of my temp phobia and staring at the temp guage for 8 hours is exhausting. To be 100% happy I need to push it in 35° plus ambient heat to be sure the gremlin is gone but today was positive :thumbup:

So if it is gone then what was the culprit? The radiator, fuel pump, viscous fan, leaking hose?, the waterpump or a combination of all of them? I dont know but I remain highly suspicious of my old fuel pump and viscous fan before the upgrade. The patrol with all the extras asks alot from the engine and its factory cooling system... maybe a simple underbonet air flow issue coupled with a faulty fuel pump?

I will report back if the problem returns or if the next long drive goes well! I hope this helps someone if they are dealing with the same thing.

Have a good one
Cheers !
Last edited by Craig Lord on 09 Mar 2020 15:54, edited 1 time in total.
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Re: Heating issue 4.8

Post by Peter Connan »

Well, that sounds good. I hope the issue is indeed sorted.
I don't think it's the viscous. At 100km/h I really doubt any fan is doing much to help.

My money is on the radiator being the primary culprit.
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Re: Heating issue 4.8

Post by Tinus lotz »

Viscus can help ...but your radiator was the problem dude seen it many times over

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Re: Heating issue 4.8

Post by Craig Lord »

Done 4 more long trips since the last post. 35° and over and no problems to report :thumbup: thank you to everyone for the help :bravo:
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Re: Heating issue 4.8

Post by hugejp »

GREAT news. :thumbup:
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Re: Heating issue 4.8

Post by JohnBoyZA »

Thank you for keeping us updated Craig :thumbup:
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Re: Heating issue 4.8

Post by Onematch »

This forum is very cool - no drama just good advice - amazing problem solved without pulling heads etc..

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Re: Heating issue 4.8

Post by Florian320 »

I replaced the water pump, viscous coupling, thermostat and the fan itself in one step.
Before my temperature would go back and forth and quite rarely also climb above 90° without any understandable reason.
After replacing these four parts the temperature is much more stable and reacts much more logical: it goes up until just above the thermostat's opening threshold to go down again.
My old viscous coupling definitely was done. It would work at engine start but (now as I hear the fan working during driving which I hadn't heard before) then would cease operation.
So in the end the change of these items also made a great difference. My old pump looked good, I just did it precautionary. So. most probably the thermostat had an issue (maybe hanging in between sometimes?). I think the gain when cruising regarding the viscous coupling is not that great, but definitely when driving slowly.
May I just add some info about the pump: I first asked at Nissan and they also told me the pump would be ZAR 700 or so. I queried why it is so cheap (hey, it's Nissan!) and was told that for these old cars they offer aftermarket parts - even it the Nissan dealer. I asked for the original Nissan pump which was as expected: more than ZAR 2500.
I then got it from Australia for about 60% of the price but took the original one as I don't want to take chances with the water supply.

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