Head Gasket on the 6.5 Diesel


Buying a project vehicle that has passed through a few hands is always a daunting journey. Having only owned the van for a few months and putting about 1200 miles on it really gives you a good baseline of possible problems. It all started with the day I picked up the van. I had a light on the dash showing something was low, thinking it was the windshield wiper fluid it wasn't a transaction killer. Now I know. The coolant reservoir was low, which is definitely a red flag. Long story short, the head gasket was leaking causing combustion gas to pressurize the coolant system pushing coolant out of the overflow. Potentially this can cause your engine to drastically overheat and bring all sorts of mayhem to your life. Luckily, the leak was very minor and went diagnosed for a good while. With the problem of a low reservoir tank slowly getting worse, I decided to look into the tell tale signs of a leaking head gasket. Google brought me to a 10 item list and i had 8 or the 10...... Also, this was the day before the Richmond Adventure Expo and two days before leaving for Overland Expo East on the other side of the country. I couldn't deny there was potentially catastrophic doom for the engine. 

So the following Monday, phone calls were made and parts were ordered. I sourced most of the gaskets from RockAuto.com and the head stud kit from Heath Diesel in Washington State. Keith and Heath Diesel was a pleasure to talk to about the 6.5 Diesel, he races one at Bonneville and holds land speed records. So putting in the same parts as the race truck was a no brainer.

Above: Passenger side of the engine. Notice the cylinder cross hatches, looks brand new. It really was a crate engine.

Diving head first into the unknown I followed some basic rules for staying organized.

1. Label Everything

2. Don't mix tools with parts

3. Clean up after each day

4. Take your time - This was a total of 10 days. Due to waiting for parts but then taking a day or two off just to get a break when getting frustrated.


The culprit, the forward most passenger cylinder had the leak. Obvious due to the rust on the head. The gasket was missing material as well. I got lucky the first try due to the fact that the heads are about 60 pounds each and getting them in and out of the van was one of the hardest jobs I had to do. Some would have buttoned the engine back up from here, but after speaking with Keith from Heath Diesel I needed to dive into the other side.

Some back story: The original engine was replaced by the prior owner with a surplus updated 6.5 Optimizer from the HUMVEE Repower Program. The engine dealer opened the motor to install head studs, which is a great upgrade. However, the installer did not do a very good job which caused the gasket failure.  Once both sides were apart I got everything as clean as possible and started assembly.

Above: Chasing all the threads to ensure proper torque can be applied

Above: Adding the supplied thread sealant for the head studs. On these engines the studs are through holes into the water jacket. If you do not use sealant, coolant can leak into the oil passages of the head causing a milk shake in your engine.

Above: Both heads back on and ready for the intake, turbo, and wiring harness.

Above: All back together and on the road