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Discussion Starter #1
Hi

My car cooling system is doing a strange thing.

It takes really long to get up to temperature.

Once it is up to temperature it is normal. Until I go on the motorway and start travelling at 100km/h the temp gauge slowly goes down from being in the middle to about a 1/4 of the factory water temp gauge.

Any ideas?

It is a N15 Sedan auto, and it pulls around 470km to 40L for city driving.
 

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Wise Cracker
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MRSN15 said:
Hi

My car cooling system is doing a strange thing.

It takes really long to get up to temperature.

Once it is up to temperature it is normal. Until I go on the motorway and start travelling at 100km/h the temp gauge slowly goes down from being in the middle to about a 1/4 of the factory water temp gauge.

Any ideas?

It is a N15 Sedan auto, and it pulls around 470km to 40L for city driving.
But it does get up to temp.? Does the heater blow hot? My thought is that the thermostat is stuck open...
 

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TwiztidKidd
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807 Posts
Try a piece of cardboard in front of the radiator (that works when it's really cold outside)... if that doesn't help it means the radiator circuit is open (something's wrong with the thermostat). There's a way to check if your thermostat is open just by pressing on the two hoses from the radiator. I keep forgetting how it's in the Haynes book. If you feel the coolant surging thru the hose then the thermostat is open.
 

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wes said:
But it does get up to temp.? Does the heater blow hot? My thought is that the thermostat is stuck open...
Yes it does get up to temp, just takes a really long time. But like I said if I'm motorway driving it starts coming down from normal (1/2) to about 1/4.

The heater seems to take a while to blow hot, but it does blow hot.
 

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thermostat. I was also thinking air in the system, but I think that'd actually cause it to overheat. have you checked the coolant level and strength? if you're low on coolant, and not enough is reaching the heater core, you won't get warm air. but my gut says thermostat.

have fun. nissan chose an extremely inconvenient and difficult location for the thermostat and housing on the GA16DE engines. it's in the back of the engine. and then refilling it without getting air bubbles trapped is a science all in its own. I think it's on a sticky here though.

since the thermostat is located on the lower radiator hose, it's kinda different. after the engine's running, the one on top will be hot. if the bottom one's hot, you've got good coolant circulation. if it isn't, then you're overcooling because of a thermostat stuck open. replace the thermostat when the engine is cold. when you take it out, look at the plunger to see if it is seated and sealed securely or if it's stuck open. sometimes the coolant will destroy the O-rings used in the factory thermostats too. and when you install the new thermostat, make sure the little hole is pointing straight up at the 12:00 position.
 

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blackmaxima88 said:
thermostat. I was also thinking air in the system, but I think that'd actually cause it to overheat. have you checked the coolant level and strength? if you're low on coolant, and not enough is reaching the heater core, you won't get warm air. but my gut says thermostat.

have fun. nissan chose an extremely inconvenient and difficult location for the thermostat and housing on the GA16DE engines. it's in the back of the engine. and then refilling it without getting air bubbles trapped is a science all in its own. I think it's on a sticky here though.

since the thermostat is located on the lower radiator hose, it's kinda different. after the engine's running, the one on top will be hot. if the bottom one's hot, you've got good coolant circulation. if it isn't, then you're overcooling because of a thermostat stuck open. replace the thermostat when the engine is cold. when you take it out, look at the plunger to see if it is seated and sealed securely or if it's stuck open. sometimes the coolant will destroy the O-rings used in the factory thermostats too. and when you install the new thermostat, make sure the little hole is pointing straight up at the 12:00 position.

Coolant not flowing through the heater core when the stat is open = overheat...
 

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Discussion Starter #7
Thanks, I'll check the bottom hose today after a drive.

Great that the thermo stat is in a hard location. I've just noticed that the P/S pump appears to be leaking. That doesn't look like much fun either to remove.
 

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MRSN15 said:
Hi

My car cooling system is doing a strange thing.

It takes really long to get up to temperature.

Once it is up to temperature it is normal. Until I go on the motorway and start travelling at 100km/h the temp gauge slowly goes down from being in the middle to about a 1/4 of the factory water temp gauge.

Any ideas?

It is a N15 Sedan auto, and it pulls around 470km to 40L for city driving.
I agree, the thermostat is stuck open, or it does not have one.

Have fun!

N.
 

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Discussion Starter #11
Twiz said:
That's the thermostat housing... kind of hard to take pics of it... I found this pic on ebay.

Thanks. Guess its the P/S pump to come off to get to it.

I assume you can do this with the engine in.
 

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i attemped this on the weekend, (thermostat housing/waterpump removal) but i had a hard time taking off the hoses behind the housing to remove it.

remember to loosen the bolts on thewater pump pulley before removing the belts. theres 5-6? bolts securing the water pump and the housing is connected to the water pump. there are 4-5 hoses on the housing that you have to remove to pull it out as a whole. i would have cut the hoses, but i cant see where they lead to and wont be able to change them

i didnt get to do since i couldnt get the hoses off. its REALLY tight in there...hopefully you have better luck
 

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TwiztidKidd
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MRSN15 said:
Thanks. Guess its the P/S pump to come off to get to it.

I assume you can do this with the engine in.
No I don't see why you should remove the P/S pump, you're gonna be working on this from the top, not from under. Just cable tie everything thats in the way (hoses, wires) to the side so you have a clear view of it and don't forget you have to refill the coolant while engine's running. Don't leave any air trapped in the cooling system.
 

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My 2000 N15 temperature gauge was swinging from 50% to 25%. On a cool night it sat at 25% on the highway and 50% through slow traffic. The heater still pumped out heat and if I used it on full it would slowly drag the temp down from 50%.

I replaced the thermostat and now the gauge quickly gets up to 50% and sticks there.

The old thermostat was stuck half open.

Here is MY procedure for replacing a thermostat on a 2000 N15 Ga16DE Manual:

The thermostat housing is located near inlet manifold at the cam chain end of the engine - a radiator hose connects to it. It is in an awkward place to work on and requires patience and perseverance!

Jack up car.

From the top unclip the cable that runs over the thermostat housing by releasing the cable tie. I used my fingernail to bend down the small release tab hidden under the protruding strap.

Undo the 2 top 10mm bolts with a ring spanner and a small 10mm socket on a short extension.

From underneath remove the lower 10mm bolt. There is a little more room to swing the ratchet under there.

Put a container the size of a sink under the car to catch coolant. Lever off the thermostat housing cover being careful not to damage the mating surfaces. Coolant will flow out.

Remove the old thermostat.

Lower car back down and remove radiator cap to drain a little more coolant. Then jack it back up.

Remove large pieces of rubber sealant and use a coarse scouring pad to remove sealant from mating surfaces. This may take a few minutes.

Soak up coolant ponding in the housing with a rag and clean and dry the mating surfaces.

Apply new sealant with a finger trying not to get it on everything that is in the way! Avoid using too much sealant that may cause stray pieces in your cooling system.

Place new thermostat in housing with the bleed valve at the top.

Screw the housing cover back on and reclip the cable. Lower the car.

I let my car sit there for a few hours to let the sealant cure but I am not sure if that is necessary.

Slowly pour coolant back into the radiator and refit radiator cap.

Turn the heater to hot and let the car warm up - this may happen quite quickly.

Drive car around the block.

Check the coolant and top up as needed. If the temp gauge is at 50% but the heater blows coolish air then take the car for another drive to push coolant into the heater. Then check coolant level again.

All done.
 
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