Posted: Apr 29 2008 at 10:47pm | IP Logged

I have an overheating issue and I have read some of the issues posted here.  A lot has been done, and still no solution, so allow me to start from the beginning.

I was driving home from a long hour drive and didn't realize it until I pulled into my neighborhood, that the engine was running hot.  I got out and saw it steaming from the radiator cap and could hear the coolant boiling.  There was radiator fluid sprayed all over the place and I think that the garage I just took it to that day forgot to put the radiator cap on all the way when they were doing thier "free" diagnostic tests.  The next day, I flushed the system several times and the fluid was rusty.  I put new coolant in and the truck overheated again.  It has about 105k miles, so I went ahead and replaced the waterpump, thermostat, all hoses and clamps, and on a side note, the timing belt, and all drivebelts.  I cleaned the radiator and changed the oil.  When I got it running again, I had the truck pressure tested and everything looked good. No leaks or anything.  I ran the truck for about 20 minutes and it started to overheat again.  I replaced the fan clutch and it still overheats.  This time, it overheats after I have been driving for close to 30 minutes.  I got on the interstate and once cruising on that at 65-70 mph for a sustained period of time (15 minutes) it starts to overheat.  If I just run around town, it has no problems.  When I was on the interstate and it started to overheat, I pulled over and checked some things.  There was no steam, odor, or noticeable overheating signs.  The upper hose was hot, but the lower one was only warm.  I would wait about 3-5 minutes and start the truck again, and the gage read normal operating temperature and I could make it about 10 more minutes before it would tell me the truck was overheating again. 

Could this be a problem with my gage or a sensor somewhere?  Waiting 5 minutes shouldn't allow the truck to cool that much.

I ran to Autozone and got the codes........just the knock sensor code.  That has been there for about 2 years now.  I'm stuck and really don't want to have to take it in. 

Posted: Apr 30 2008 at 6:45am | IP Logged

Is the new thermostat in correctly or upside down?  Is the radiator itself clogged?  Your note on rust could be an indicator.  Are the fins in the radiator clogged with leaf or insect debris? Is the lower hose being "sucked closed" by the action of the water pump?

Just a few ideas to check out.  Hopefully others will add their thoughts!

Posted: Apr 30 2008 at 3:10pm | IP Logged

I had almost the same issue their is 2 sensors on top of the t-stat housing the one closest to the front of the motrr is the problem I replaced both if I remember they were under 50.00

Posted: May 05 2008 at 4:20pm | IP Logged

..

tcaff11;

... You might pull a couple of spark plugs to see if you have carbon build-up or a lean burn fuel ratio. Carbon will screw up every thing in the engine including the EGR. Lean Burn will cause over heating on the highway.

You guys keep us posted as things turn out...Thanks...

Posted: May 05 2008 at 6:03pm | IP Logged

When you replaced the water pump, are you sure you got one that rotates in the right direction?  I don't know about Nissan pumps but some Chevys, etc have pumps that run one way or another depending on what belt setup is used. 

Also, I am still thinking about the rust you found in your first post.  This can be i9ndicative of a lot of corrosion buildup in the system that is getting stirred up and clogging passages.  Have you done a power flush of the block?