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Discussion Starter #1 (Edited)
im worried about the high temp in my 4.2 gq,
it gets to over 100c when driving around town, but if the heater is on the max it goes to is 90c.. on the hwy with the heater on it sits on 80c (about a quater on the guage).. but when i stop and turn the car off the overflow bottle fills a pushes about 500ml of water out, in the bush it sits just under the H.. i have flushed the system out several times.. the fan seems to kick in but doesnt seem to cure the rising temp..
has anyone got an idea what the problem would be
 

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The nutty professor
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yeah recheck your radiator cap and make sure the radiator hose builds pressure when warming up and holds pressure when hot, also make sure that there is no pressure when the motor is cold, could also be a faulty thermostat , replace it and see what happens , the fact that it runs cooler on the hwy points me towards the fan or air flow through the radiator problem, also possible is the fins on the water pump could be corroded
 

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All the above. It should run around 80-90 deg C all the time. Running cooler on the highway does point to fan or water-pump, a stuck 'stat would affect it all the time.
 

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BORDERTREK 4X4 & FABRICATION
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Maybe it's cooler on the highway because there is more airflow anyway. Getting to H on the gauge in the bush indicates to me blocked up coolant tubes in the radiator itself and the radiator isn't cooling as efficiently so, the rad cap is probably doing it's job releasing pressure into the overflow so as to not over pressurise the whole system.
 

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pull ur radiator out and take it to a car wash and give it a good clean out.
 

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i would take it to a radiator joint and get the inside cleaned as it sounds to me like a blockage on the inside, but while its there they will give it a real good clean inside and out.
 

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BORDERTREK 4X4 & FABRICATION
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i would take it to a radiator joint and get the inside cleaned as it sounds to me like a blockage on the inside, but while its there they will give it a real good clean inside and out.
Even a core clean doesn't always fix it. Sometimes the crud sets like cement in the tubes and cant be be mechanically removed, been there done that, and a new fresh rad has fixed the problem.
 

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Discussion Starter #11
i have replaced the rad cap, the thermo stat has been taken out, i took it to a rad joint they cheaked the surface temp on the system and said its all normal. some people have been saying it might be the head gone. ill cheack the water pump this weekend
 

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Right Turn Clyde
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You need to have the basics sorted first , a new cap and you must have a thermostsat in there otherwise your coolant doesn't stay in the radiator long enough to cool giving you fluctuating temperature and pressure problems.
Check all the radiator hoses, are they soft?. Are they colapsing when hot and blocking flow?. Do you have a body lift?, the lower hose tends to kink if not shortened to suit therefore blocking flow. Is your fan shroud fitted properly?. Simple things to check before guessing a head problem.
 

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Discussion Starter #14
well it seemed to have fixed it self.. i went to the bush yesterday and didnt get over 90c
 

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You need to have the basics sorted first , a new cap and you must have a thermostsat in there otherwise your coolant doesn't stay in the radiator long enough to cool giving you fluctuating temperature and pressure problems.
Check all the radiator hoses, are they soft?. Are they colapsing when hot and blocking flow?. Do you have a body lift?, the lower hose tends to kink if not shortened to suit therefore blocking flow. Is your fan shroud fitted properly?. Simple things to check before guessing a head problem.

The 'stat is a real subjective issue with several schools of thought. One says that without one in the coolant moves too fast through the engine & radiator to remove heat. Another says that BECAUSE the coolant is moving faster, it's actually more efficient. Without actually getting into a water gallery yourself with a thermometer it's pretty hard to say either way.
My own practical experience concerns a fully-loaded LWB Sierra in Kakadu NP in September (30 deg +) which threw the fan-blades in Jim-Jim Ck. Couldn't get one for love or money of course, even in Darwin. After driving from Darwin 1/2-way to Rockhampton running hot all the way, stopped for a couple of hours sleep, removed the 'stat & drove to Rocky, then Maroochydore, hooked up my Cousin's 14' Tinny & drove home to Canberra, all on normal temp. Once home, replaced 'stat, bought new fan, removed steel grille behind radiator that'd snapped off the old fan & the little jigger was still running strong when I sold it 2 years later - including a big Fraser Is trip.
My GQ's 'stat was jammed open so it always ran at around 75 deg once warmed up & NEVER went over 90 deg, even in 40 deg heat doing low-range mountain-climbing. Given the head-problem-rep of the TB42 I was always happy with that. Just needed to slide some cardboard in front of 1/2 the Rad. in winter (-6 deg mornings) to help warmup.:D
Otherwise, yes, check & replace EVERYTHING until the problem is solved.
 

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BORDERTREK 4X4 & FABRICATION
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Yeah but removing the thermostat is just masking the problem temporarily. If the cores are blocked it will just get worse over time. The thermostat needs to be in there so the engine warms up to proper temps asap and cold runs especially short ones is the quickest way to wear out an engine faster. eighty8 is spot on about the coolant staying in the radiator long enough to cool down properly when it's hot otherwise we could all run radiators the size of tranny coolers :rolleyes:.
And dimmy said nothing about what the ambient temps were or how he was driving it yesterday.
I still say the symptoms he described point to blocked coolant channels in the radiator or the water pump impellor is shagged and not moving much coolant.
Also 118C is within normal temp range for a TD42 (is this a TD42?) so the cap shouldn't let out pressure at 100C.
 
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