...So maybe don't help.

Fun fact, if you search for install help questions for a Nissan Xterra, all the top search results are for an offroad Jeep site. This one.
And whoever wrote all the info I found was a bit of a hipster doofus.

So here we go. I'm writing down the symptoms on the white board and seeing if any of you is any help with diagnosing something other than Sarcoidosis. At least we'll give the internet more reasons to poke its search nose here.

Problem: Overheating

Parts replaced:

• Radiator
• Water pump
• Cap
• T-stat
• Fan clutch

Additional:

• Added Tranny cooler
• Bled upper intake coolant valve
• Last night Geoff helped me for 6hrs lowering the radiator and shroud 2" back to stock height (has 2" body lift)

The clincher: Only overheats on hills, 65+mph. Never while running parked or on surface streets or at red lights.
Being that it's the summer, I found that turning the heater on when it's acting up, dropped the temp back down. I learned today this was a fallacy. In fact, just turning the AC off, let the engine return to normal operating temperatures.

Further testing today revealed that the RPM's may not even be related as previously thought.

Constant: 113° outside temp

• Test 1: 65mph | 2500rpm | AC-ON | overheat=YES
• Test 2: 65mph | 2500rpm | 5mi | AC-OFF | overheat=NO
• Test 3: 88mph | 3200rpm | 5mi | AC-OFF | overheat=NO
• Test 4: 70mph | 4000rpm (OD-OFF/3rd gear)| | 5mi | AC-OFF | overheat=NO

So because of that I believe I can rule out air flow, speed, and engine workload.

So theorize for me now that I've tried all the mechanical stuff.

One theory, albeit weak in my mind, is that when the AC is on, the condenser sitting in front of the radiator is extra heating the air before it hits the radiator....

Move

I should have just added a poll

The only thing that makes sense givin the only time you have a problem is up hill, is water pump.. Where did you buy your water pump?

Long shot, but how are both of your hoses? I've seen before when they get old and mushy, under a heavy engine load they actually collapse all the way, or enough to restrict the flow of coolant. Back to the water pump, I"ve also come across water pumps from Vato Zone, CarQuest, Napa, etc.. that are just junk. It's bit me enough times that I will never buy an aftermarket water pump if a dealer one is available. I've had to do to many jobs twice because of it. I"ll keep thinking on it.. but that's all I got so far.

Also, you could just remove your A/C all together, you might gain 3 HP :) lol

Colorado FTW.

NotAvis wrote:The only thing that makes sense givin the only time you have a problem is up hill, is water pump.. Where did you buy your water pump?

Long shot, but how are both of your hoses? I've seen before when they get old and mushy, under a heavy engine load they actually collapse all the way, or enough to restrict the flow of coolant. Back to the water pump, I"ve also come across water pumps from Vato Zone, CarQuest, Napa, etc.. that are just junk. It's bit me enough times that I will never buy an aftermarket water pump if a dealer one is available. I've had to do to many jobs twice because of it. I"ll keep thinking on it.. but that's all I got so far.

Also, you could just remove your A/C all together, you might gain 3 HP :) lol

Colorado FTW.

I don't know who you are NotAvis. I don't know what you want. If you are looking for ransom for Avis, I can tell you I don't have money. But what I do have are a very particular set of skills...

I know the post was a long read and you've probably got a lot to do right now, but I believe I've ruled out the hill stuff and engine load it seems. It did it on the way to Avis's wedding and there were no hills.

*I've actually had the WP replaced twice since the trouble began.

Keep thinking. I appreciate it.

Elmer at Scottsdale Protech researched and if you thermostat is not a factory part it will not work right. So since its the cheapest part start there. Or we need to presure test it again and leave it overnight. And do a leak down test on the cylinder heads. He says it could be head gaskets, but start with a factory thermostat.

46204621462246234624 :))

I agree with showboat. You have a circulation problem related to a pressure problem.


Miles

have you ever had the ac compressor replaced? never overheats with ac off? only on?

On the A/C side, how does the A/C work? cold, kinda cool?? if the system is under or over charged that will change how the system preforms & how the refrigerant across the condenser temp will be, shouldn't be enough to make the motor over heat but ya never know, another possibility is the compressor is starting to go & is putting an additional load on the motor at higher RPM's (or its a pressure issue @ higher RPM's and its having to work harder)

Scooby. I just drained it and recharged it last night before he did although. But not sure. l his test. It might have a possibility

Motor is under a load rather you go up a hill or not. The hoses will collapse as the pressure builds.

I agree with the t-stat needing to be factory as well, makes a difference.

Is there room to add an electric fan?

2ndchance wrote:46204621462246234624 :))

FTW!

ALL good answers so far.

I'm having trouble letting go of the AC being a culprit if it is the only constant when it overheats. Matt, I've never replaced the compressor. Blew cool before we evac/charged and blows cold after. It seems so simple of a problem that your idea had gone through my head also of the pulley bearing or something halfway to seizing is dragging that belt slower when load spinning.

Avis, I can't see an electric fan helping at freeway speed. There should be enough ram air flow at speed. The e-fan is a great addition if overheating is happening at slow desert speeds.

I'll try the t-stat again. I believe I've read the supercharged model has a 10deg cooler t-stat.

I can't see or smell any leak and there's never any water missing.

Another vote towards a wonky compressor issue expressed on a Nissan board:

it sounds more like the compressor is putting a load on the engine that it can't handle.

do you have gauges? we can check the freon pressure and see if it's high. could be a blockage or sludge making the compressor work, or just a bad compressor.

Does Jonathan have the same issues in his truck?

sweathog wrote:Does Jonathan have the same issues in his truck?

Who's Jonathan?

sweathog wrote:do you have gauges? we can check the freon pressure and see if it's high. could be a blockage or sludge making the compressor work, or just a bad compressor.

Does Jonathan have the same issues in his truck?

Jonathan has not had this problem.
I thought Geoff had gauges on it when we worked on it? He did comment that it seemed like there was extra oil in it when he pulled the hoses off the condenser. Maybe he can chime in on that.

A buddy of mine with the same year Xterra was having the same issue. He discovered that his head gasket was leaking. He fixed that and the problem was solved. Now I am not saying to go out and change that gasket because it is not an easy fix but doing a leak down test might help you discover the problem.

Just talk with my buddy he also said to check the timing. Now, he said to check it without the TPS hooked up.

alanzona wrote:Who's Jonathan?

I clicked reply to answer and then I realized what you really meant...