Can anyone tell me what is causing my slight overheating problem in a Nissan Navara diesel from these clues: Gets quite hot going up hills and takes a while to come down again when descending, but doesn't boil. Top of radiator is hot. Bottom of radiator is cold. Hot both sides of thermostat. Top hose is hot. Bottom hose is hot at top but cool where it is joined to the Radiator. If I take off the radiator cap when cool with motor running I can not see any coolant movement. I don't want to have the radiator cleaned if it is the pump that is faulty, or either of these if it's just the thermostat stuck closed. Can anyone tell me from these symptoms what part is faulty!
jmma,
Jul 31, 1:37am
My guess is blocked radiator with hot at top and cold at bottom.
morrisman1,
Jul 31, 1:54am
check the viscous fan is operating correctly
gammelvind,
Jul 31, 3:09am
Surely if the bottom hose is cold then the water isn't circulating as the hot water enters from the bottom!
monzaman,
Jul 31, 7:29am
NO-water always goes in top of radiator,this one will be atleast 50% blocked.
neryl1,
Jul 31, 7:47am
id eliminate the cheapest if you can put the thermestat in yourself then drive for a while if no different can you take the radiator out yourself turn it upside down hose it out look at likely hood of it being blocked like had any additives through it for overheating or leaks.
mellisa2000,
Jul 31, 9:43am
blocked
intrade,
Jul 31, 9:46am
well you will have to find out it could be any of these or all of em. Start with what the coolant looks like and when it was last changed! if it was never changed then you could have all things broken and coroded by now plus all your coolabt hoses will have gone brittle from inside also= huge big bill to fix it correctly again.
intrade,
Jul 31, 9:49am
your discription of post 1 could be a non opening thermostat. it could also be a blocked radiator or it could be the waterpump has got no impeller left no more. Now as above if your coolant is nice and green or red and was changed on time =every 24 month. then you can rule most likely expensive corrosion out, leaves you with a faulty thermostat you then remove that and see if it cools now with no thermostat fitted
falcon15,
Jul 31, 9:51am
take the thermostat out and put it in boiling water to see if it opens. normally when the radiator is partially blocked you would still get a hot bottom radiator hose. If there is no air con radiator in front on the radiator you should be able to feel the radiator core when its hot to see if theres any cool spots. If there is then its blocked but you need to make sure the thermostats opening first
intrade,
Jul 31, 9:52am
to test the waterpump you simply have to turn on the internal heater and see if it gets hot air when the engine warms up. If it is cold then you have to find out if your waterpump still has its impellor or not.
frank1,
Jul 31, 10:24am
Radiator--is partially blocked--as u have been told,and possibly vanes have been corroded from water pump.
praxxis,
Aug 3, 7:00am
Thanks to all you knowledgeable people. I have taken all your answers on board and have decided to remove and test the thermostat first, then put in some radiator flush and flush out the system, then fresh anti freeze, then if it's OK then, I'll be well pleased, but if not I'll take out the radiator and have it professionally cleaned. I think now that it may not be the water pump as it is not leakingand the antifreeze has always been changed in my ownership of 3 years. The overheating has not been apparent in that time as it only takes me to work and home (5kms on the flat) so it may have been a problem before I got it. I only realised it got a bit hot when I used it for a 100km trip recently, and had to ease off going up hills.
intrade,
Aug 3, 7:24am
ease off going up hills. could also be a thermal switch for your fan. some cars have a dual stage fan sensore like fiat tipo. my one always got warm in auckland before the fan kiked as the first stage was going to die. then the first stage was gone and the secound started to die like the first. this did mean the fan hardly did spinn when it got to 90+ degree and i had to turn on the heater to cool it up hills. When hunting for new parts it became apperant that the thing was shurly at fault as the symptoms mached the dualstage sensore fault. fitted the one from my other car and woala problem was fixed. this can also lead to exxess fuel consumption on petrol cars. my one is diesel no electronic controlls
quickstitch,
Aug 3, 8:04am
dont rule out the waterpump impellor being eaten away.I had to do one in my mates wife's 4X4 (i think it was a Navara), and it was the second waterpump it had gone thru.
jimjonesy,
Aug 3, 7:23pm
Do a flow test on the radiator, fill it up, then remove bottom hose, it should come really pouring out, if just a small bit or trickle - there's your problem.
koriemouse,
Aug 3, 11:55pm
My guess would be thermastat, mine had identicle symtoms and changing thermastat fixed the problem. $27 and 30mins work. good luck
praxxis,
Aug 4, 7:28am
I have seen a Navara waterpump with eaten away veins too. Just hoping it isn't the pump as they are expensive for this vehicle as they come with the viscous coupling for the fan. Thanks jimjonesy, I will try the flow test you suggested. Anyone know of a test for the waterpump without removing it and lookingat the impellor!
intrade,
Aug 4, 7:51pm
i told you to put the heater on other test is to poke a screwdriver in the hole and see if you can feal some vanes . i once found none on a toyota vista like that and woala removed none there and it had rapid overheating issues including a blowen headgasket.
praxxis,
Aug 6, 9:17am
Oh yeah, thanks intrade, I,ll also try the screwdriver (or similar) in the hole to see if I can feel any vanes. The heater does warm up, but very slowly, taking about 5 kms to start demisting the windscreen. Perhaps that's blocked too! It's starting to look fairly obvious that the radiator is blocked.
srrolla76,
Aug 6, 12:04pm
you have a blocked radiator. easy
praxxis,
Aug 7, 5:40am
YEP, I think so too. Out it comes next weekend. I've been quoted $100 from a radiator specialist, if I remove the radiator, they will take off the top and clean out the core then replace the top if it's still serviceable (plastic), if not it will cost a bit more. I intend to run some radiator flush through the system before removing the radiator to clean out the rest of the system, unless someone tells me this is not a good idea.
praxxis,
Oct 8, 2:55am
Thought it about time I reported the results :
Removed and tested thermostat, which was OK, so re-installed it.
Removed the radiator. Clamped hose into heater hose and gave system a good flush out. Took radiator to specialist to clean out. They reported that it was badly blocked but cleaned up like new. They suggested replacing the plastic top however as the core was now good but the top may not stand up to re-clamping, so I gave the go ahead and that's what they did. I picked it up the following day and had it installed by lunchtime. Ute now runs perfectly. Creeps up to about halfway on the temp dial on the steepest long hills and the back down to almost nothing on the way down. Brilliant. Thanks guys for your advice.
ralphdog1,
Oct 8, 4:44am
Someone that reports back, thus improving the knowledge of all. Top marks and thankyou.
mugenb20b,
Oct 8, 4:46am
Replace the thermostat.
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