Nissan overheating mystery

Nissan11

Nissan11

Well-Known Member
Joined
Nov 29, 2005
Location
Marston, NC
Ok, for about a year my v6 Nissan frontier had been leaking coolant. I couldn't find it no matter how hard I looked. Finally, I had a shop pressure test it and they found a hose leaking behind the thermostat. About two weeks before I got the leak fixed the truck started running hot. At first it was only on real hot days, but it's slowly been getting worse.
At first I thought it was air in the lines. I spent a lot of time bleeding the cooling system. That seemed to help and the truck ran cool for 2 days. Yesterday I went to uwharrie for a day trip and made it about 1/5 the way around rocky mountain loop before the truck started running real hot. If I parked the truck and let it idle it would slowly cool down.
However, when the needle was in the red zone, I could cut the motor off and immediately turn the key to the ACC position, the needle would drop down to the normal operating temp. As soon as I started the truck the needle would jump back up. I blasted the heat and got back on 109 and the temp slowly dropped back down to normal.
When I got home I changed the radiator cap and thermostat, but that actually seemed to make it slightly worse and the truck has been running fairly hot all day.
I parked the truck this evening in preparation to change the water pump and noticed there is water dripping from where the AC condensation leaks, but I haven't had the AC on, I've been blasting the heat.
What is going on here? Am I right to assume that my problem has to be the water pump??
When on the highway the temp is hot, as soon as I come to a stop light the temp drops down to normal, so I think the fan clutch is good.
 
The fan clutch seems good. Several times when the truck was running hot I popped the hood and the fan was running.

I DID have the defroster on so that explains that. I hope to have the water pump changed by midnight.
 
Hope you went ahead and changed that timing belt while you were in there! If for some reason the problem persists grab an IR temperature gun and check the temperature at various points on the radiator, you could have some tubes blocked and the radiator cannot dump enough heat at high engine loads. Also, check for mud and debris stuck between the AC condenser coil and the radiator. One time I dunked mine in mud good enough to block quite a bit of airflow and the truck ran pretty hot. Took a lot of water dosed between the two to clean things up and get it cooling right again.
 
I'm not changing the timing belt. I changed it 30k miles ago and opted not to change the water pump while I was in there.

I couldn't get the crank pulley off last night. The puller that I rented didn't come with the right bolts so I had to go get them this morning.
 
Is there any way to tell if the old one is bad? It spins freely and looks fine...



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How much play is in the shaft? And the more important question is did you learn your lesson about replacing the water pump when you replace the timing belt? It seems to me that you have an air flow issue, not a water flow issue meaning that your radiator is either plugged with mud and debris or has come apart inside and the coolant isn't in there long enough to give up enough heat to keep the engine cool.
 
Did you ever change the thermostat? Sounds like it could be stuck open as well and at higher rpms the water isn't staying in the radiator long enough to cool down.
 
I changed the thermostat yesterday, and I learned my lesson about changing the timing belt and water pump at the same time.

There is absolutely no play in the water pump shaft. I spent the last hour and a half scraping the old water pump gasket off the motor. I'm going to start putting everything back together now. Is there a way I can do a flush at home with a garden hose?
 
Yea, since you've got the front of the engine apart, before you put the fan back on spray water from the back side of the radiator out and see what comes out. 200k work of dirt and grime and leaves and grass clippings will start to come out. You might even pull the radiator out of the truck since you've already got the coolant drained and spray it that way.
 
I've got the radiator out of the truck. I put this radiator in about 90k miles ago, it's not the original. Can I spray water into the coolant ports on the motor to try to flush the motor?
 
You can try and see if any comes out. If you still are overheating really see if its just at slower speeds or while your moving. If its just at slower speeds I would check the fan clutch.
 
The truck runs perfectly cool when idling on 95 degree days, it' only overheats with the AC on or while driving.


I just put the timing belt back on. I should have it back together shortly after noon.
 
I got the truck back together, went for a drive and it immediately started running hot. I don't know what to do. I cleaned the radiator real good while it was out of the truck.
 
What's the inside of the radiator look like? Probably still have air in the system from the pump swap. But before sounds like you have air flow problem, my jeep did this and it was the radiator full of gunk from old coolant.


Sent from my Tapatalk using IPhone.
 
The inside of the radiator is kind of an orange color but it doesn't look like there is any debris.
I sprayed water through it but nothing weird came out.
 
I don't know what else to do other than get the entire cooling system pressure flushed. I guess it's time to take the truck to a shop and I really didn't want to.
 
Jack the front of the truck up and bleed it that way. Odds are at this point you just have air in the system. It gets super heated and goes by the temp sensor and it appears the engine is overheating.
 
This morning I parked the truck on a hill with the front up high. I let the truck run 15 min with the cap off and never saw a single bubble, the coolant just slowly overflowed.
Just now, after 15 min at operating temp, I notice the rad cap was cool to the touch even though the upper hose was too hot to touch. Is that normal?
 
No that's not normal. What was the lower radiator hose like? If it's too hot to touch shoot it with a IR temp gun. You should have 20 degrees difference between the two. If not, the radiator isn't doing it's job.
 
OK. At this point, the water pump is working and so is the radiator. It really sounds like you've got air in the system. May want to run the piss out of it for a bit to get everything flowing and try and force the air out.
 
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