2002 Pathfinder overheating.. :(

[kasilvia]

So I have been getting frustrated chasing a heating problem on a 2002 Pathfinder with the VQ35DE. It only overheats when it is at speed. I checked the fan clutch and decided to replace on grounds of wear. I also replaced the thermostat, on the grounds it got hot. I let it run after replacement at idle for at least 20 mins after it reached operating temperature, and the gauge was half mast as it was supposed to be. I take it down the road and within 3 miles I was watching the needle climb... So I put the heat on full blast and the gauge starts to drop. This leads me to believe the radiator is backed up. I also notice that even after bleeding the system, I would wind up with "air pockets" in the lower radiator hose. It almost seems like the pump cant force the coolant through the radiator, because it builds alot of pressure on the top side and has air pockets in the lower.I am knowledgable in automotive repair, I am a technician by trade. However, I would like to see if anybody has any other ideas as to what might be going on, i.e. past experiences with this problem. I dont relish spending my fathers day under this truck instead of with my son, so if I find the radiator to be fine tomorrow, does any one have any suggestions from there? I know the water pump is driven by a gear, is it a common part to fail on these? The truck has 110k, and I appreciate any help you guys can give me with this one. Thanks in advance,Luke

[kasilvia]

Please, any help? I dont have my FSM so I cant read up on it.

[munny]

I am having intermittent over heating and was wondering what you did to resolve.

[email protected]

[lali707]

I am having the same signature for overheating on my 2003 qx4. Replaced the thermostat, ECT and did a coolant flush. At Idle the temp gauge is fine. However at speed the temp gauge climbs quickly. Is the radiator clogged? Is there a way to verify before replacing.

[Chuck Tribolet]

I am having the same signature for overheating on my 2003 qx4. Replaced the thermostat, ECT and did a coolant flush. At Idle the temp gauge is fine. However at speed the temp gauge climbs quickly. Is the radiator clogged? Is there a way to verify before replacing.

Well, for starters, with the engine cool, drain a bit of coolant into a clean container so the top of the radiator is visible. Look in with a flashlight.
Does it look like the inside of a beer can? Go drain a beer to have a good comparison.

Is the coolant a clear green?

Was the coolant you drained before the flush a clear green?

Have you gently cleaned the outside of the fins with water from the engine side (best to pull the shroud before hand, and BE GENTLE, the
fins are ever so easy to bend).

Did you burp the radiator after you did the coolant change? You have a 2003, so it's an automatic. the '01 automatics had two burp points,
one just in front of the firewall dead center, and one on the front of the engine (my stick shift doesn't have that one).

When you replaced the thermostat, you did replace the whole thing including the aluminum housing?

When you refilled it, what antifreeze did you use? Did you use distilled water?

It's overheating under load. If that's happening at speed, it's NOT the fan system as the motion of the truck through the air pushes
plenty of air through. It's unlikely to be the water pump. Water pumps fail by leaking, but they still pump water. Either something
is preventing water flow, or something is preventing air flow.


Chuck

[VG33QX4]

probably head gaskets leaking

under load they are leaking, check to see if there is bubbles in the coolant, if so this is the issue. I have seen it before.

[rayde862003]

I have a 01 pathfinder has 156,000 miles with the 3.5 runs smooth no ticks has alot of power as from what i could tell. i was coming home on the highway 10 miles max and notice it heating up to over heat, but it didn't let it get that far. after stopping and letting it cool i made it home. I can let the it run forever and it wont overheat til i drive it. Along with the overheating i don't get no heat til i hit anywhere from 35-45 mph and its light heat. to get the heat i should get i have to go 60- 65 mph. I change the thermostat on the front of the engine i flushed heater coil. I also ran it at 2000 rpm to get air pockets out. Have any idea what it is? I put $700 down on this ran great on test drive but should've took it farther but it ran so nice and smooth. I cant take it back no warrentee

[Chuck Tribolet]

Did you burp the system? There's a rubber cap just in front of the center of the firewall, just below the hood line. You
need to remove the cap and slowly top up the system. When done, install the rubber cap, then install the rad cap (do
it the other way round and the burp vent will probably spit a little antifreeze on you engine). Be very careful removing
and installing clip that holds the burp cap, the clip likes to go flying.

The FSM shows another burp point on the front of the engine, but my '01 (which is a stick) doesn't have that one.

Also, how does the rad look inside?

Chuck

[rayde862003]

it looks clean. I don't know it its original because its really thin but other then it being thin looks like radiator goes to it. I didn't burp it that way because i couldn't get that rubber cap off. Is it ok to cut the rubber cap and can u even get 1 at auto part store. I did burp the system by using radiator cap and running int a 2k rpm it did bubble alot but only can do that for 4-7 minsat a time or risk getting to hot ( i dont like it over 3/4ths of the way to hot) i know alot of cars do run that but it will go up more if i dont turn it off. I never overheated or let it get to the hot mark. and i aint getting no heat or defrost feels like a/c til i get to like 45-60 then i am getting alil heat, but thats only at times. this morning i took it back i didnt get no heat I took it back to the place i got it. they only do little fixes but there leaning toward the water pump because it don't over heat till ur driving so there thinking the fins on water pump.I aint so sure but i am sure there going to want me to pay for it. it was as is no warentee i put 700 down and i have to pay 75 ever 2 weeks til i pay the left over 1700 it was 2200 plus tax title and 30day tag. othe then the over heating it needs a front bumper cover.

[Chuck Tribolet]

The rubber cap will come off if you twist it in the middle. Wrap the jaws of a small pair of slip-joint pliars with
duct tape and have it it. After the first time, the rubber cap is easy.

Your "no heat until on the highway" sure sounds like a stuck-open thermostat to me. Start with a cold engine. Take
the radiator cap off, and start the engine. Do you see flowing coolant through where the rad cap attaches? Might be
helpful to run the engine at 2K RPM while looking (needs a buddy or spouse). If you see flowing coolant when cold,
that's a stuck open thermostat.

I don't think it's the water pump. Water pumps fail in a couple of ways: leak, or fail to pump which will cause an
overheat at both idle and highway. Fail to pump is pretty uncommon.

Chuck

[rayde862003]

no flow but alot of bubbling. i changed the thermostat it comes with the neck front middle engine

[rayde862003]

i has to be leaking or more bubbling out then i think i added 2 gal aready trying to breed air out

[Chuck Tribolet]

There shouldn't be any significant bubbles. Bubbles are usually a sign of a blow head gasket. Does the oil look milky?

Chuck

[rayde862003]

no its nice and clean even the inside as far as i can see. it runs like its brand new except for it overheating and the heat

[CanuckQx4]

Sounds like air in the heater core to me

These trucks are notorious for being difficult to bleed air, my truck will be fine for a month and then all of the sudden I can rev it in park and hear the air/bubbles rushing in the heater core.

Pull the heater core hoses off in the engine bay, passenger side at the firewall and run some water through them

[rayde862003]

i have done that already

[CanuckQx4]

Im curious when Chuck has that rear burp spot open during bleeding

[Chuck Tribolet]

My process is:

Fill radiator and install rad cap.
Run engine just a bit (a couple of minutes).
Fill radiator.
Optional: jack front end.
Pull the burp cap.
Wait five minutes.
Fill Radiator and install rad cap.
Install burp cap.
Fill overflow tank to min line.
Go for a drive around the neighborhood and come home.
Pop the hood, have a couple of cold ones while things cool off.
Check the level in the rad. If it's come down, repeat the above.

Chuck

[rayde862003]

ill keep that in mind i took it back to the buy here pay here place eventhough it was as is and i am making payments he said it was the water pump and having a shop do it. i get it back tomarrrow ill post as soon as i get it and let u know if they fixed it