Posted: Apr 01 2008 at 2:56pm | IP Logged

First of all, make sure the clamps on your radiator hoses and heater hoses are tight.  You can tighten them easily if they are the SS worm clamps but not if they are the spring tension clamps.  You can also get leaks from intake manifold gasket failure.  Any leaking gasket will cause a pressure test to indicate a leak so you can't just assume it is a head gasket. 

Is there any evidence of coolant in your oil?  This manifests itself as a milky looking glop on your dipstick and on the inside of the oil filler cap.  This iIS indicative of a head gasket that has failed and is allowing coolant into the oil.  You can also pull and examine the spark plugs to see if one or more cylinders is pulling coolant into the cylinder through a break in the head gasket.  How badly did you overheat your truck a year ago?  If severe overheating occurred, you might have warped a head and allowed the gasket to start leaking.

If you have coolant in the oil , don't drive the truck.  You'll ruin the bearings.  Have it towed to a shop for repair.

Posted: Apr 04 2008 at 7:58pm | IP Logged

Don't assume it is a head gasket issue.  My 2005 4.0 had the same symptoms minus the visible leaks and the heads were removed at Nissan and taken to a local performance shop for analysis.  The initial findings at Nissan indicated that cylinder 3 was @ 30% normal compression.  Further review from the shop found that two other cylinders had low compression which they surmized was due to incorrect valve factory settings.

They are now looking to replace the entire engine under warranty (19800 miles). 

The dealership initially thought it was a head gasket issue until the latest findings.  Go to a good shop and you may start looking for a replacement engine as the labour costs involved will be huge.  My truck has been at Nissan since last Wednesday - there are over 35 hours of labour on my truck so far but I'm fortunate since this is under warranty.