[Tmcallister2500]

Hey everyone so I’ve replaced the thermostat (after market part) tested it, replaced the water pump (after market) no leaks, fan works, radiator doesn’t leak, replaced the coolant temperature sensor (after market) would it be the wiring connecting to my gauge cluster? I took the temperature sensor off and it still shows hot and from letting it sit for a few hours, it goes straight to hit within 10 minutes, talked to some guys at the part store, no typical signs of a cracked head or head gasket, but used an exhaust fume detector on the radiator and it shows I have a fume leak? would a crack head or head gasket cause my truck to show hot?

 

[bauertime]

If that test shows exhaust gas in the radiator, then the head needs to come off to check for the cause. Or you could try some Blue Devil type stuff to repair it for a while.

 

[Tmcallister2500]

If that test shows exhaust gas in the radiator, then the head needs to come off to check for the cause. Or you could try some Blue Devil type stuff to repair it for a while.

Appreciate it, not going to add anything to it tho, already went through that with my last truck, going to try to fix it before it gets worse. Thank you.

 

[CT_Nismo]

The only move you have is to take off the head. But the head may not be the cause of the overheat.

Are you able to measure the temperature at the top and bottom of the radiator while the overheat is occuring?

 

[Tmcallister2500]

The only move you have is to take off the head. But the head may not be the cause of the overheat.

Are you able to measure the temperature at the top and bottom of the radiator while the overheat is occuring?

That’s what I’m doing today I’m going to buy a mechanical thermostat to test it, and I’m going to pressure test the cylinders.

 

[RamTest]

That’s what I’m doing today I’m going to buy a mechanical thermostat to test it, and I’m going to pressure test the cylinders.

A laser thermometer also works good, and has many other uses.

 

[CT_Nismo]

A laser thermometer also works good, and has many other uses.

As Ramtest wrote, a laser temperature instrument is a real handy device and is perfect for this application. "Shoot" the upper plenum/lower plenum. Or the upper and lower radiator hose. Lasers are cheap.

Here is the theory. If you have good temperature drop across the radiator (say 30 °F), engine heat is being dissipated into the atmosphere. If not, the radiator is not working to remove heat.

 

[Tmcallister2500]

As Ramtest wrote, a laser temperature instrument is a real handy device and is perfect for this application. "Shoot" the upper plenum/lower plenum. Or the upper and lower radiator hose. Lasers are cheap.

Here is the theory. If you have good temperature drop across the radiator (say 30 °F), engine heat is being dissipated into the atmosphere. If not, the radiator is not working to remove heat.

Lower radiator hose cool, upper hot, around the radiator and the temperature coolant sensor gets up to temp but not past temp. around the engine 180-190f nothing above, all 4 cylinder have 175 compression, no air pockets in radiator hoses, I think my over heating issue is false information, gets hot within 5 minutes even tho it takes longer to actually get up to temp, coolant sensor replaced, still reading hot on my dash, last thing to do is replace dash.

 

[Tmcallister2500]

Lower radiator hose cool, upper hot, around the radiator and the temperature coolant sensor gets up to temp but not past temp. around the engine 180-190f nothing above, all 4 cylinder have 175 compression, no air pockets in radiator hoses, I think my over heating issue is false information, gets hot within 5 minutes even tho it takes longer to actually get up to temp, coolant sensor replaced, still reading hot on my dash, last thing to do is replace dash.

I used a laser

 

[Tmcallister2500]

I used a laser

I get heat aswell

 

[CT_Nismo]

Lower radiator hose cool, upper hot, around the radiator and the temperature coolant sensor gets up to temp but not past temp. around the engine 180-190f nothing above, all 4 cylinder have 175 compression, no air pockets in radiator hoses, I think my over heating issue is false information, gets hot within 5 minutes even tho it takes longer to actually get up to temp, coolant sensor replaced, still reading hot on my dash, last thing to do is replace dash.

This is good news. Very good compression so no head gasket failure. Radiator is working to remove heat. I think you have a false positive on coolant temperature and I would look into the sensor as the culprit.

 

[Tmcallister2500]

This is good news. Very good compression so no head gasket failure. Radiator is working to remove heat. I think you have a false positive on coolant temperature and I would look into the sensor as the culprit.

Yep! I’m very glad, but on my 4th cylinder the bottom of the spark plug looks black, no oil in the socket, and the truck is idling high at 2 on the takometer, abs engine shakes, fuel injection? I put cleaner in it and replaced the iacv?

 

[Tmcallister2500]

Yep! I’m very glad, but on my 4th cylinder the bottom of the spark plug looks black, no oil in the socket, and the truck is idling high at 2 on the takometer, abs engine shakes, fuel injection? I put cleaner in it and replaced the iacv?

And* instead of abs

 

[keith56]

Are you having to add coolant? If so, how much? If you are loosing any coolant, and there are no visible external leaks, then you have a breach in the head gasket. If you are adding less than a cup a week r quart a month, then there is an additive that will work. Most all manufacturers put it in the radiators at the factory, but only one sells it to the public and that is Subaru. It is called Subaru Cooling system Conditioner and is available from a Subaru dealer or from Amazon. But this only works on very small leaks. If you are loosing more than a cup a week, it's too late.

Another sign of a breached head gasket is if a plug is "too clean". Coolant "steam cleans" the plug tip, gives it a sand blasted look. The plug with the black tip is not from a coolant leak. I'd replace it and maybe the coil too. That cylinder may also have a leaky fuel injector, but a shiny black tip is from unburned fuel. Shiny more often means excess fuel, dull black indicates misfire or oil burning due to bad rings.

 

[bwthor]

Someone please correct me if I'm wrong, but I'm under the assumption that there are two temp sensors on these engines (VG33's at least, not sure what OP has). One for the gauge (single wire), and one for the ECU (2-3 wire connector.) Get a scanner and see what the ECU is reporting for engine temp.

 

[Tmcallister2500]

Are you having to add coolant? If so, how much? If you are loosing any coolant, and there are no visible external leaks, then you have a breach in the head gasket. If you are adding less than a cup a week r quart a month, then there is an additive that will work. Most all manufacturers put it in the radiators at the factory, but only one sells it to the public and that is Subaru. It is called Subaru Cooling system Conditioner and is available from a Subaru dealer or from Amazon. But this only works on very small leaks. If you are loosing more than a cup a week, it's too late.

Another sign of a breached head gasket is if a plug is "too clean". Coolant "steam cleans" the plug tip, gives it a sand blasted look. The plug with the black tip is not from a coolant leak. I'd replace it and maybe the coil too. That cylinder may also have a leaky fuel injector, but a shiny black tip is from unburned fuel. Shiny more often means excess fuel, dull black indicates misfire or oil burning due to bad rings.

I’m not having to add any coolant, cylinders came back with good compression, replaced the coolant temperature sensor still not luck but my dash is also reading my speed and rpm’s wrong aswell, thank you for the information about the sealer tho, that hopefully won’t have to come in handle but if does will try this first, the only other reason beside it showing it’s overheating did I think I blew a gasket was I did an emissions test on the radiator where you use this liquid to pull air through the radiator and if the color of the liquid changes yellow, it means you have emissions leaking into my radiator even tho my coolant isn’t bubbling.

 

[Hawairish]

Maybe I missed it, but what's telling you that you're overheating? Code, OBDII scanner, gauge cluster? Any codes?

Also, did you change the thermostat to address this issue, or as preventative maintenance beforehand? Do you have the previous thermostat still? Did you put a 170° or 180° unit in?

As dumb as this is going to sound, I had recently been chasing an underheating situation on my other Nissan, a 2004 Pathfinder. Truck's been throwing a code because it's not reaching operating temps. Well, despite the factory service manual specifying a 170° unit, and having recently replaced it with a new 170° unit as part of preventative maintenance and going through an absurd amount of troubleshooting effort testing absolutely everything ever since, I've determined the problem is because I'm using a 170° unit. The one I pulled was a 180° unit and I didn't notice nor expect it. Again, FSM spec is 170°. I never had a problem with the old unit.

1998 Frontier is spec'd at 170°, too, but 180° units are available. Perhaps that's what's in it now and it's causing higher temps?

 

[Cusser]

When you changed the temperature sensor - did you replace the correct temperature sensor? There might be two or three temperature sensors on some engines, and just one will go to the gauge.

 

[CT_Nismo]

Maybe I missed it, but what's telling you that you're overheating? Code, OBDII scanner, gauge cluster? Any codes?

Also, did you change the thermostat to address this issue, or as preventative maintenance beforehand? Do you have the previous thermostat still? Did you put a 170° or 180° unit in?

As dumb as this is going to sound, I had recently been chasing an underheating situation on my other Nissan, a 2004 Pathfinder. Truck's been throwing a code because it's not reaching operating temps. Well, despite the factory service manual specifying a 170° unit, and having recently replaced it with a new 170° unit as part of preventative maintenance and going through an absurd amount of troubleshooting effort testing absolutely everything ever since, I've determined the problem is because I'm using a 170° unit. The one I pulled was a 180° unit and I didn't notice nor expect it. Again, FSM spec is 170°. I never had a problem with the old unit.

1998 Frontier is spec'd at 170°, too, but 180° units are available. Perhaps that's what's in it now and it's causing higher temps?

Cars and trucks naturally over heat which is why they all have radiators. The T-Stat plays an important role in quickly arriving at the right operating temperature. Regardless of the temperature setting, your truck will rise to proper operating temperature sooner or later. How are you measuring temperature?

I would put a big piece of cardboard in front of the radiator and run the truck. The temperature of the coolant should rise. If not, I suspect the temperature reading. Take out the cardboard else you will overheat.

 

[Hawairish]

Cars and trucks naturally over heat which is why they all have radiators. The T-Stat plays an important role in quickly arriving at the right operating temperature. Regardless of the temperature setting, your truck will rise to proper operating temperature sooner or later. How are you measuring temperature?

I would put a big piece of cardboard in front of the radiator and run the truck. The temperature of the coolant should rise. If not, I suspect the temperature reading. Take out the cardboard else you will overheat.

I measure temps with an infrared thermometer but that doesn’t mean squat when the ECU reports it below 170. ECU reported consistently in the 135-160 range. I could drive the truck for hours (and literally did several 6-8 hour trips) and still threw codes. Idled for 30 mins. Sensor and t-stats (my truck has two) were confirmed functional to spec. I was able to raise temps using cardboard, and needed to do so to satisfy driving patterns for emissions readiness. Literally checked everything, couldn’t find an actual problem. Bottom line is the FSM spec appears incorrect for my truck.

Nonetheless, I have my solution and did not intend to detract from the OP’s problem.Just providing a backstory to suggest a 170/180 tstat could be the difference.