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overheating gq

Tech Talk for Nissan owners.

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overheating gq

Post by purplebus »

age old question searched but didnt find answer. gq4.2 diesel with factory gu turbo and gu series one inj pump, front mount intercooler & ac cond manual on 35's.

fitted new 3 core auto rad and shroud (biggest gq one they had) , cooling system flushed,new waterpump, tried 2 new thermostats, checked fan and hub 3 4x4 mechanics say perfect, co 2 and pressure test rad (perfect), no oil in water or water in oil. been dynoed and fuel mix etc is perfect.

temp is perfect around town(82 degrees on a/mkt guage) even on hot days with ac on has no a/c fan either. but wants to heat up at 100km/h , under load or when towing(normally to 104 but to 115 on a hill i couldnt stop on.cools down to normal after 1-2 mins. cut centre of thermostat out same prob but not quite as bad (only just), took thermostat out but same as cut down version. any ideas.

can i get a massive radiator to fit in from somewhere.?? tried 3 different gu alloy ones but they are 2 wide for the chassis rails as i dont want a body lift( have 5" susp). fan draw is excellent even with the front mount you can feel by hand and mech's say perfect.

vehicle will be burnt if i cannot rectify shortly as i am going nuts trying to solve this. lockers, winch, seats and cage will be removed before ignition..
only the first roll hurts, then its a ride..
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gq overheating

Post by paul44b »

Hi Mate, How much you want for the cage??? just joking..
have you got big lights, winch etc on bullbar?
try packing up the back of the bonnet to let some hot air out..I have the same sort of problem but I haven't tried to look for solutions yet...Paul
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Post by Rhysta »

Put the thermostat back in, its there for a reason..

Id look into the airflow threw the front of the car, but it could be anything really..

Have you got a egt guage?
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Post by Ibsn »

To me it sounds like you really shouldn't have a problem, I suppose the obvious thing to ask is, have you got big spotties blocking the air intake, and or have you removed the ford/nissan badge off the grille, as this is all extra airflow you could be getting into the motor.

I run no engine fan, run 14 psi and its non intercooled. And standard radiator with roughly 15% corrosion effecting it. I have one 14inch thermo fan which i barely need to use. And diesels cool themselves at idol, unlike petrol. It will only run hotter if Im running AC. I have removed the FORD badge, and have 2 spotties infront of the grille.

Also a note to remember, as I have done some reading on glycol. your mix should be minimal. It is true that the more you put in the higher your boiling point is, HOWEVER the more you put in the LESS effective your cooling system is. This is due to the fact that glycol has less energy transfer then water. So it therefor means your cooling system is less effective no matter how many fans you ram through it. We dont live in conditions that need ANTI FREEZE.

Most people if their engine is overheating they crank in more antifreeze aka glycol... WRONG.. this will only make the problem worse, however your coolant wont boil at 140 degrees.

The TD42 is primarily a cast iron block, so corrosion is hardly an issue. I know of people running almost no glycol and just water wetter through their engines. This is people who tow 2-3 tonne caravans around with no intercoolers on the turbo like my fathers GQ.

He did however find it only ran hot, chuggin up a hill, max boost on a steaming hot day, but rectified that by since putting in an oil cooler, and an extra heater core like that found inside the cabin, he has mounted it behind the flattest part of the alloy bull bar. This is as effective as running your cabin heater if your over heating. Other then that towing under normal conditions never caused a heat issue.

How much glycol mix are you running in the engine?
Last edited by Ibsn on Wed Feb 06, 2008 3:48 pm, edited 1 time in total.
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Post by Rogue Patrol »

Does it have a body lift?

I was told that a body lift can disrupt the airflow at speed causing this problem....??
I was also told at the time an A9x style scoop can remedy the problem by creating a low pressure area in th engine bay and allowing more air through the radiator.
Makes sense but don't know if it's fact or fiction.

Mine (atmo diesel) gets up to half on th factory guage up a big hill but usually runs at 1/4.
It has a 2" bodylift but I haven't tried th scoop idea yet.
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Post by Ibsn »

Oh and NEVER EVER EVER take out the thermostat. That is the dumbest thing (sorry) that you can do to an engine.

My mates 308 v8 hilux, obviously runs hotter then standard motor, when he bought it off this fella, I was fairly convinced that it should be heating up sooner and a really cold night run out to cruiser park the temp sat on about 60 the whole way (i ended up putting a towel across the grille infront of the radiator to let it keep its heat in). Running an engine WITHOUT an thermostat IS THE WORST THING YOU CAN DO TO YOUR ENGINE!!!! your engine will take forever to heat up and wont be able to regulate its temp ever.

since putting the thermostat in to his v8, it heats up in 4 mins, and has never run hotter then it had previously with no thermostat. Around 90-100

Those wiz bang engineers kinda put it there for a reason. You wont get any more flow through your thermostat when its fully open, as apposed to it not being there at all. Im sure they calculated your water pump flow rate and the flow rate you can get through the thermo. to be roughly the same. Removing it all together will achieve nothing but pain for your engine! A unwise and poorly educated decision! Yet lots of people seem to do it!

MY td42 also had no thermostat when I bought it, I picked up on it immediately, I shudder to think how many years it ran without one. However, it went from takeing 20 mins to get up to operating temp on a morning run to work, and now it takes less then 5-6 mins. It has never ever run hot. Even when the old viscous fan (and no electric fans at this stage) did nothing but 90% free wheel.

IS your temperature gauge telling you the right scale? I just find it hard to believe its running that hot after all the cooling work you have done to it! But like I said, whats your glycol mix!
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overheating

Post by purplebus »

it has a custom pipe bar on the front which we modded for more air flow(more so my friend who builds em and cages did as my welds are like blu-tak) the spottys are out of the way of flow.we took complete bar off and was still the same.
put the amount of coolant in as specs on bottle. got the more expensive brand as well.is their a brand you would recommend?
what is a egt guage??
no bodylift and the thermostat is bak in as well tried that as last resort.thought maybe 1 was dodgy but 2 now.
have the factory gu scoop over turbo.
as you can see i have tried lots of things. could accept if i was getting huge horses but i went all factory to avoid this drama.
may be a long weekend bbq with it on the sunny coast.
was told the fan clutches can work perfect one minute then not at all the next. to rectify this you open them up and put the toyota fan oil in them???
the factory guage reads normally about 1/3 but was going up to the h line.
i had a 350 chev in one and the top half of the guage measured only a 5 degree change when we put the aftermkt temp guage in.but the diesel is approx 20 degrees in comparison. have changed sender in eng as well.
the truck is such a capable and reliable old thing it is only the heating which annoys me.
when the turbo was fitted it was plumbed into the heater lines as most of the others i have seen.have swapped the lines over as one dumps on top of sender unit but nothing changed.should they be plumbed somewhere else?
thanx heaps for the help.
Last edited by purplebus on Wed Feb 06, 2008 4:19 pm, edited 1 time in total.
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Post by Ibsn »

Seems Strange! Especially since you've done so much work to it!

You should be able to hear the fan really roar once it kicks in. This is why my father ripped his out and replaced it with 2x14inch thermofans. Because the liquid silicon inside the viscous clutch seems to be unreliable, and the quantity must be just perfect - too much and its locked all the time, too little and it wont kick in at all. - and you don't want it working all the time, as your cooling a cold motor and your wasting horsepower and your generating excess fan noise from the front of your car!

If the viscous fan is not working reliably, this will definitely cause your engine to overheat under heavy load and low speed - low airflow?

I just bought a 14inch thermofan from supercheap for 89 bucks! You can get the 16inch ones for 99 bucks. (Last time i looked at fans there were all round the 300 dollar mark)

They seem like really good build quality for the money, and come with the full wiring loom, fuse and relay and are reversible to mount on the rear of your radiator. however at the end of the day, a working viscous engine fan and just as importantly a shroud to control the airflow can pull HUGE amounts of air when your engine is doing 2000 - 3000 rpm.

I run 35's and like I say 14psi non intercooled, bullbar with spotties half in the way, and a standard Rad. And run no fan, no shroud, and one 14inch thermo in one corner of the Rad. And it only needs to be turned on on a hot day sitting in traffic with the AC on. So I would be checking your temp gauge cause you shouldn't have a problem!
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overheating

Post by purplebus »

with the gauge have changed the factory sender and fitted a/mkt temp as well. they both say hot hot hot. not keen on thermo fans as i do a lot of water and had thermos die on me before. i always remove and wash rad core out as well after every trip as it fills with mud and boat people on the deeper puddles.
it doesnt heat up in traffic on a hot day with ac on or off or at low speed only 100km/h, uphill or towing. might go borrow another fan off a mate and check that option.
tricky problem isnt it. should i see a rad specialist instead of the mechanics. they are good reputable mechanics who race 4x4 as well.
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Post by Ibsn »

Im outa ideas... unless your water passages throughout the engine block are clogged? Im not sure if you could put high pressure and high volume water throughout a cold block to clean it.

I'm sure I'm only young compared to the more senior members on this forum, i'm just sharing my knowledge from what I know between my fathers Gq and mine.

Pulled apart many motors gearbox's, fair bit of mechanical hands on stuff etc
But I'm outa ideas! Im sure someone on this forum has the same issue. If your viscous clutch fan is kicking in and the shroud is on, and your glycol mix is alot less then 50/50 your pretty much doing all you can, aside from the other ideas my old man has modified his truck to get rid of excess heat. Surely someone has some better ideas?

Maybe the front mount intercooler is blocking the majority of the airflow to your radiator seeming it has to pass through that then the aircon condenser

AND the air that does get through is preheated and slow moving making the issue worse when working hard to maintain 100 or under heavy load?
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Post by tj81 »

My 2c

I would bet that the issue is airflow. As mentioned, to get to the radiator, the air must pass through both the intercooler and the ac condensor before it gets to the radiator.

I would think that by the time this happens, the air is already pre warmed, and also has far less air speed.

Check to make sure that the ac condensor is not clogged with mud and stuff to make sure your getting maximum airflow to the radiator.

not sure how practical but if you can try a top mount intercooler somehow to see if that also assists.
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Post by dirtyGQ »

i think it is a radiator water flow problem ,buy a standard gq radiator $350 or have yours cleaned by the radiator shop. The pull the tanks off and brush thru the cores.
I had the exact same problem and got a new radiator and now runs ona quarter and way under half going up kilcoy mountain with the van on.
THE GRASS MAY BE GREENER ON THE OTHER SIDE BUT YOU STILL GOTTA MOW IT.
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Post by dirtyGQ »

by the way also get a proper block flush.
THE GRASS MAY BE GREENER ON THE OTHER SIDE BUT YOU STILL GOTTA MOW IT.
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Post by lowexf »

Mate mine was doing exactly the same thing, you say you have replaced the radiator but nothing was mentioned about the hoses. Feel the radiator hoses, if they are really soft, then throw them and fit new ones, at high engine speeds the hoses contract and slow down coolant flow, thus overheating the engine. I replaced my top and bottom hoses and problem solved.
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overheating

Post by purplebus »

just emailed the local aussie auto and ordered them. thanx heaps will keep you posted.
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Post by Ibsn »

lowexf wrote:M Feel the radiator hoses, if they are really soft, then throw them and fit new ones, at high engine speeds the hoses contract and slow down coolant flow, thus overheating the engine.
Food for thought, but I'm not sure how that works when the cooling system is pressurised. I woulda only replaced them if they are clearly aged. They have to be softish to allow the engine to rattle round on its mounts while the radiator remains a part of the body, otherwise your gona snap the welds to the connection pipes off the radiator if they were stiff. When the engine is at operating temp, these hoses when squeezed are clearly under pressure like a balloon. Seems impossible that they could contract, when they are on the positive side of the water pump and heat pressurised.

Then again its worked for lowexf - and he had the same issue as you. So its worth a go. I just don't see the physics in it. Would be blown away if that were the issue!
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Post by dirtyGQ »

e bottom hose can suck in if it has gone soft restricting water flow.
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overheating

Post by purplebus »

spoke to the aussie auto blokes and they said it is quite common for the hoses to collapse. apparently years ago some hoses used to have a spiral wire through them before they realized it would corrode away...
willing to try anything at the moment. got onto a bloke who work with the v8 supercars, rekons if they can keep those cool my stinky old patrol will be a job for their apprentices and at the right price.amazing who you meet at one mates wedding after a few rums.
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Post by dirtyGQ »

make sure they do not try and lug you with an aluminium radiator,these thing make matters worse because they are too thick to draw air through at idle.
Seriously replace hoses then radiator if the hoses don't fix the problem.
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Post by tj81 »

dirtyGQ wrote:i think it is a radiator water flow problem ,buy a standard gq radiator $350 or have yours cleaned by the radiator shop. The pull the tanks off and brush thru the cores.
I had the exact same problem and got a new radiator and now runs ona quarter and way under half going up kilcoy mountain with the van on.
Where can you get a standard GQ radiator for $350 ???

I went through this after an incident with a tree, and the best i could do was around thr $500 mark for a reco'd. I ended up importing a genuine nissan one, nissan price $700 RRP
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Post by dirtyGQ »

red devil radiators at capalaba,$350 including gst was a NATRAD radiator exact same radiator as standard.
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Post by Ezookiel »

I have gone through a similar issue.
Would boil on long hill climbs, but no issues around town and at idle.
Did all the things you did. Various viscous clutches, various thermostats (Only the genuine Nissan ones open at 72.5 from memory, others open later, so use only a genuine Nissan diesel thermostat)
Went with a 4 core Aussie Desert Cooler, slight reduction, removed grille totally, no real change. TWO Bonnet scoops, some minor improvement, but still would boil.
Ended up going the whole hog. New engine, new turbo, front intercooler, extra transmission cooler, and still hits 80% of the gauge, but at least it doesn't boil now.
Runs between 25% and more often about 50% of the gauge all day around town no matter how hot it gets outside, aircon and all. But long hills, and up she goes.
I've given up trying to solve mine, and just take it real easy and don't travel with anyone who I wouldn't want to slow down (such as club convoys) so just one mate and myself now.
I know it's the last Nissan I'll ever buy, it's cost me a mint.
I have wondered whether the scoops should be faced backwards to create a low pressure side, but the factory face their forward, so mounted mine accordingly, though the factory ones are for the IC, where mine are just for engine bay temp reduction. Maybe I'll experiment with them, as one has come unstuck at the back, so to redo it properly I'll have to take it off anyway.
A genuine Nissan DIESEL viscous clutch, and genuine Thermostat that opens at a lower temp than most others. Oh, and make sure it's also a genuine diesel FAN, I found mine had a petrol fan which has one less fin and a less aggressive angle on it.
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Post by dirtyGQ »

EZOOKEIL,what radiator did you end up running as aussie desert coolers are not the answer.
I can make any car run cool .(unless it is fooked)
In most cases a genuine radiator fixes the problem ,but failing that a custom shroud (that is set up to create a vauum effect) and twin thermo's that draw more air than any clutch fan could ever draw.
Also flaps on the inside of the shroud that open at highway speeds.
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Post by GUJohnno »

Ezookiel wrote: Oh, and make sure it's also a genuine diesel FAN, I found mine had a petrol fan which has one less fin and a less aggressive angle on it.
Mine had the same. Replacing that and lowering the shroud to match the BL dropped the temps by a 1/4
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overheating

Post by purplebus »

saw 2 radiator experts 2day. one said alloy rad $700 or use a seperate tank as the commodores have. to run an extra litre or 2 of fluid.

the other said that the 3 core radiators(mine) more often than not are not as effective as the 2 core. suggested a full flush of the block, ripping the rad out and taking the tanks off to make sure they are not blocked. sometimes eng scum can dislodge at any time.

ready for the freaky bit........ suggested travelling up and down the highway at 100k's and noteing? temp at certain spots then taking thermostat out and drilling little holes around the flat plate to let extra water flow at a restricted rate.

started 82 degree then up to 93 in no time then 98 approx with a/c off( i have no a/c fan though). pulled up and drilled approx 10 1/8 holes in thermostat. put it back in started it up and then the mother of all storms kicked in. waited for the rain to stop before heading off. air temp had cooled down considerably but i was certain that even god himself didnt want me to know if this would help.

flogged the absolute guts out of the old girl with the a/c on (no fan remember) and it wouldnt get over 82 degrees. will be heading down the same stretch of road tomorrow in the midday sun to check it in similiar conditions hopefully.
if this works i will get a full flush of eng and rad to make extra sure.

this sounds like a very common problem with the gq's i hope i can help other poor soul like ezookiel if i can sort this.

nearly thought of getting rid of her as well, but she drags her 3 tonne ,7 seats , my beautiful wife , 3 kids and fridge carrying butt to cruiser pk, around the superior all terrain for 2 events, finally up the hill drags after 4 attempts last year(non turboed) and up any hill i jam the old thing up so i can forgive it for the one problem she has given me. it has never NOT GOT ME HOME.

will keep you guys posted. going to garage for some quiet time with her... :lol:
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Re: overheating

Post by bogged »

purplebus wrote:. suggested a full flush of the block,
stand there and watch when they do the reverse system fluch.... you will be :shock: :shock: :shock: at the amount of shit that will come out.
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Re: overheating

Post by dirtyGQ »

[quote="purplebus"]saw 2 radiator experts 2day. one said alloy rad $700 or use a seperate tank as the commodores have. to run an extra litre or 2 of fluid.
the other said that the 3 core radiators(mine) more often than not are not as effective as the 2 core. suggested a full flush of the block, ripping the rad out and taking the tanks off to make sure they are not blocked. sometimes eng scum can dislodge at any time.

The original brass radiators work best, i have see people use 5 core ally radiators and often starts a whole new problem of not enough airflow.

Good luck you sound like you are headed in the right direction.

Just be careful with the thermostat because if it runs too cool you will start glazing bores.
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Post by GOT MUD »

im glad to see it might be starting to come good for you Shane let us know how it goes on midday sunny run ;) but i might have to get the cordless out also

i hope it all works id hate to the see bus turn charcoal black id miss watching it doing superior you guys put on a good show

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Post by its aford not a nissan »

i have actually made mine to run hotter as it seems to run better hot

i put a new thermostat in and it sat on 1/4 on the temp guage all the time only raising to half on long steep hills but the fan was constantly enguaged and roaring its head off , so i adjusted the thermostat a little so it doesnt open till around 90-95 degrese and now the motor runs smoother and quieter the fan doesnt cut in till around half way on the guage and very rarely cuts in at all so i am not loosing power with the fan running all the time , it still goes a little over half on big hills but never boils or looses water

works for me anyway

remember deisels like it hot
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overheating

Post by purplebus »

woke up this morning and it is sunny. cant wait for air to warm up so we can head off to the test track. (kunda park past ettamogah pub to caloundra turn off). just a quik note the rad is a brass copper and yesterday with the holes in the thermostat it was running at about 80 degrees around town a drop of 2 degrees on the full thermostat run. wish me luck.......................

if you see a 90 kg down in the dumps, drunk looking fellow at the ettamogah pub this arvo looking across his schooner at a charcoaled wreck on the highway. make sure you buy me another drink..
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