The Nissan Path

This morning my 2001 Pathfinder overheated as I was driving on the highway. If anyone can help, here are a few details:

- It is REALLY cold here in Kansas City. Subzero at night.
- Previously, it did not give me heat at idle, only when driving.
- Assuming from this that there was air in the line, I attempted the air bleeding procedure, adding an approximate 50/50 coolant mixture, cheap brand coolant
- I got no heat while driving. This afternoon, I finally got heat after driving a few minutes.
- It overheated on the highway, and coolant sprayed out on the inside of the engine near the coolant overflow tank.

Any advice is appreciated. I am thinking it is a bad coolant mix that froze overnight. Could be thermostat or water pump too...

Usually if a water pump fails, it'll leak coolant out the weep hole. It is rare for a VQ water pump, which is driven by the timing chain, to fail (although it's possible). A thermostat that is stuck shut will overheat at idle as well as on the highway. As far as being air-bound, this would only occur is the coolant system was run low on coolant or serviced, of if there is a mechanical issue, such as a blown head gasket, cracked head or cracked block. If the coolant mix was insufficient protection for the temperatures in your area, it may have very well cracked a block, which could cause the symptoms you are experiencing. A restricted radiator could also cause similar symptoms. You may want to pressure test the system for leaks. If there are no leaks, you could inspect the spark plugs for signs of unusually burning, do a compression and cylinder leakdown test to check for a possible blown gasket, cracked block or head. A chemical analysis can also be done to check for excessive hydrocarbons in coolant, which would indicate an internal engine failure. A radiator shop could flow test the radiator, or an infrared thermometer could be used to check for hot and cold spots on the radiator while the engine is running.

Thanks. So last night i flushed the radiator after learning that i should not have diluted my previous antifreeze with tap water. Everything seemed fine on the side roads this morning, but as soon as i get on the highway, it overheats again.

You put tap water into your cooling system? If so, I would drain and put some straight antifreeze into the system.

If your diluted coolant gets too cold, it will gel, and turn into slush. Slush doesn't pump very well.

My guess would be that the thermostat is stuck shut.
The last thermostat that I changed had a small hole in the disc to allow for a small bit of flow even when the disc is fully shut. The purpose for the hole, I believe, is to help bleed air out of the system after work has been performed. In cold weather the small amount of flow through the hole would provide just enough cooling at idle and slow speeds but, not enough at highway speeds. Another possibility could be a partially clogged radiator.

That sounds like a likely theory. One thing I didn't mention is that the thermostat was replaced a year ago (I didn't own it then) at the dealership, and the radiator was replaced at the same time.

I wonder if the thermostat could get messed up that fast. Or maybe the tap water and cold weather made it stick. But still it sounds like this is what is going on.

Question: Can I remove the fan shroud without removing the fan? Is it in two parts that can be separated?

It sounds like the car has a history of overheating. You might want to check all the hoses carefully and change them out as you see the opportunity. When you change the thermostat also change the elbow hose in the vicinity of the thermostat. It's hard to get to and just as hard to even see. Better to change it in your driveway than on the side of the road. There's three other hard to get to small hoses between the firewall and the motor that you need to check if you notice a slow loss of coolant.

You are correct sir. I bought the truck a couple months ago and luckily have all the service records. I wish I had seen them before I bought. However, I am not noticing a loss of coolant.

Hooligan wrote:It sounds like the car has a history of overheating. You might want to check all the hoses carefully and change them out as you see the opportunity. When you change the thermostat also change the elbow hose in the vicinity of the thermostat. It's hard to get to and just as hard to even see. Better to change it in your driveway than on the side of the road. There's three other hard to get to small hoses between the firewall and the motor that you need to check if you notice a slow loss of coolant.

I think you're talking about the VG33E engine. He has a 2001...which would have the VQ35DE engine.

I am indeed thinking of the 3.3. (Done that before)
Maybe you could clear something up for me. It is my understanding that the switch from the 3.3 to the 3.5 was during the 2001 model run and that some of the early 2001 pathfinders came with the 3.3 and the rest came with the 3.5. I have seen some pathfinders referred to as 2001.5.
Would you know offhand when that switch was?

I believe it switched in August. Mine is a 2001.5 as it was built in October. But I believe the 2001.0 was a VQ35 as well.

Well, it's not the thermostat. I just pulled it and it tested fine. Back to the drawing board.

How can I check to make sure the water pump is working? Can I run the engine with the coolant cap off the radiator and watch for water flow?

If the pump is working well, I guess there would be a surge of coolant upon acceleration of the engine, but only once the thermostat is open.

SMJ probably has a better way to test.

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skipfletcher wrote:How can I check to make sure the water pump is working? Can I run the engine with the coolant cap off the radiator and watch for water flow?

Yes, you can...make sure you start it when cold. Also, have you tried the cardboard trick? Cut a piece of cardboard big enough to block the radiator and drive around to see if makes a difference. If you don't overheat out on the interstate it means the blast of cold was indeed freezing the coolant thus blocking the circulation through the radiator......It's why you see big rig trucks with radiator "blankets" or covers that can be closed or partially open.