Let me see try. I will get back to you on that.

Yes it does.

I did read there is an air vent on the 4.0L but I have yet found a location.

That hose leaking on the tank is what undermines pressure.

Side note Advance Auto has a 140 and 180F thermo.

Explain to me please how the hose leaking undermines pressure? If the radiator is under pressure isn't that hose out of the system?

"Advance Auto has a 140 and 180F thermo." What is this?

Does the upper big hose have pressure on it when warm? I thought it had none. The overflow tank is integral to the cooling system. Lose pressure there and the system loses pressure.

Two different temperature thermostats.

No pressure on the upper big hose but it is hot.

No pressure on lower hose it is cold.

I haven't been able to determine if either of those hoses leak because I can't build any pressure. One pump and fluid spurts out of the cap and the tank hose.

Does the radiator leak if the regular cap is on?

From the cap? It doesn't appear to. I saw some dampness on the plastic engine cover that may be steam but I haven't determined that yet.

The reservoir has a pressure cap I see from pics. Yes?

My reservoir does not have a pressure cap just a regular.

The reservoir has two feeds. One from radiator neck and one to engine so I don't think coolant rages through it all the time like on some cars.

http://forums.pelicanparts.com/uploa...1637445424.jpg

However, if that tank pressurizes during operation that may be where your leak is if you are saying you see wetness at the hose.

If it is part of the pressurized system it will remove pressure from everywhere in the system.

Thanks Bob

I will take a closer look at the tank and hoses in the morning. I didn't even relaize there was a lower hose.

So I took a closer look per your recomendation. It does appear the tank pressurizes as you suggested. Fortnately I had the original radiator cap and threw that on. The system seems to be pressurizing but something is still seems out of whack.

After putting on the pressure cap, filling up the radiator, taking it to the beach ramp and purping the system per your directions, I took it for a test ride. I was esentially taking the same route as described above so I had some milage and occurence points as measurments.

Prior to the drive I cleaned off any spilled coolantand dried the surfaces to the best of my ability. I then took brand new white shop rags and wrapped them around the radiator cap and the overflow tank. If anythng was coming out of them they would have green wets spots.

I drove about three miles stopped and checked, all good and heat is pouring out the vents. At about mile ten into the ride I turned the heat off and put the windows down a few seconds to cool off. Windows up heat back on high.

At mile eleven the temp of the heat began to cool off. I pulled over to check the rags. Perfectly dry. Opened the overflow to relive pressure a slight hiss. The radiator appeared full. Put the caps back on drove home.

The heat never came back up to full temp. Pulled in the driveway rags are dry, radiator is down about a quart. I guess that could have been a air?

Pulled the drivers plugs to look and smell, all good. I will do the passenger side tomorrow.

Where is the heater core?

Sounds like air I’m the system to me since you are losing heat.

Passenger side behind the glove box. Yes, first thought was air. The 2nd Gen Xterra is notoriously hard to burp air out of the system. That is why as Bob suggetsed elevating the front running the vehicle filling the radiator and repeat.

I did remove the heater hose at the fitting and fill until coolant came out.

I am not compleltley convinced I have all the air out of the system yet since putting the pressure cap on the overflow tank. I will burp the system again and take for a test drive.

Rrrrrr, this thing is driving me crazy.

Yesterday took for the longest test drive yet about twenty five miles. Got to my destination squeezed the hoses before turning off engine. No pressure. Slightly turned the radiator cap not his or steam. Radiator looked full.

Looked around the expansion tank some coolant but not much. Noticed some wet spots on the driver door so looked in the wheel well. The wheel well was fairly wet directly below the expansion tank.

Today took the expansion tank out checked for cracks and leaks, no apparent issues, checked the hoses all holding pressure.

Is the water pump dead? Or plastic fin broke off and is clogging water jacket?

I’ve read the whole thread…definitely a head scratcher.

Strange that it’s not overheating.

I don't know where to go next but the water pump? I would think not if I have heat?

I wanted to see if I had flow through the engine but not sure how to go about that?

Edit: and I would guess maybe the thermostat isn't opening due to the curren temperature here 44 degrees? Although it was in the sixties yetserday. If the thermostat isn't opening no flow through the block correct?

And this hose (the lower hose) plumbs into th heater core. Again, I took this whole thing apart this morning and all appears to be leak free including the tank.

http://forums.pelicanparts.com/uploa...1637961447.jpg

Find out what's leaking in the passenger side wheel well. I mean no duh, but that's the dealio. Gotta kill the leak. Maybe given time invested, buy the whole expansion tank assembly?

Heater core hoses with a pin hole can spray really far and confuse but there should be some hint of where it originates from.