6.5 gaskets and seals

[Missy Good Wench]

Many people seem to have loads of questions about gaskets and seals on the 6.2/6.5 diesels.

Gm used a variety of sealing techniques on these engines over the years.

The 6.2 from 82 to about 91 had a two piece felt/rope seal on the crankshaft rear main.

These seemed to be fine but could be the cause of leaks.

These engines do/can produce a fair amount of internal pressures from the normal blowby and the designers were trying to eliminate the problem areas.

Starting in 91 late in the 6.2 and on into the 6.5's through 2000 +++ the rea main was machined differently (Block and cap) to accept a one piece seal that was installed into the block using a special remover installer tool.

The pan did not need to be removed as long as the tool was available.

When doing a rebuild, care must be taken to install the seal properly and squarely in its bore.
The edges of the part line on the rear cap must be coated with either an anerobic sealer or (as I do) high tack.

The rear pan seal can be installed into its groove using high tack in the groove and the two side pockets.

Now the factory used a silicone goop on the pan rails and the area of the front covers sloped lower flange.

I have found that the new felpro pan gasket set with the two piece contruction works very well.

Seal the rubber rear pan seal into the groove in the main cap and then apply silicone sparingly along the pan rail of the block and the lower flange of the front cover.

Apply an extra amount of silicone goop in the areas where the pan gasket meets the rear rubber seal band and in the crease area at the junction of the pan and the front cover.

Stick the gasket to the block and cover, making sure that the tangs on the rear of the gasket side pieces engage the rubber seal band at the rear main.

Align all the bolt holes along the rails and the front cover.

Apply silicone to the gasket as above and then set the pan in place.
Install the bolts and snug down carefully working from the inside out to the ends and from side to side in a back and forth manner.

Make sure the gasket rail pieces are still engaged in the rubber end piece.

The silicone should squish out at the rails and the corner areas slightly as the bolts are snugged up.

after sitting over night, you can go back and tighten the bolts slightly more but dont get crazy.

The torque specs are listed but I usually use a speed hand and one hand to snug the bolts.


The front cover seal (crank seal) os a simple no brainer.
Use a suitable tool that fits over the seal and drive in flush with the cover.

Make sure the cover is sitting flat when tapping in the seal.

The gasket kits come with a gasket to go between the timing cover and the block. Use silicone between the cover and the gasket and the gasket and the block. (NO LEAKS THIS WAY)

The water pump has a gasket that goes between the pump backplate and the timing cover.
Same thing, use silicone on the gasket.

Now the factory used an anerobic sealer between the backplate and the cover.

NOOOOOOOOO use a gasket and silicone then it wont leak.

Now the intake manifold gaskets that fit at the ports can go on dry. The gaskets have little plastic lign up pins that press into the heads and keep the gaskets right spot on.

NOW

The valve covers are a BITCH. They are feeble and can be distorted easily when removed, especially if the are stuck good.

Make sure the cover flanges are flat and straight.

Clean the cover flanges real well to remove any and all OLD silicone sealer.
Wipe down with BrakeKleen.

Wipe down the head flange where the cover seal.

Apply the High temp Orange silicone sealer about 3/16 thick to the covers flanges.
Carefully sit the cover on the head and insert the bolts. Snug the bolts down going from side to side.

Dont get crazy with tightening the bolts. The silicone needs to remain between the head and the cover about .035" thick so dont over tighten

Just snug on the covers.

Allow the silicone to set up then you can snug just a tad more..

Other small gaskets such as the oil return flange for the turbo uses a gasket. Same program, lightly silicone both sides of the gasket and install the bolts.

Dont be tempted to use gaskets on the Valve covers. They will leak, ask me how I know this.

These steps will help keep an engine dry and clean for many many miles.

This is not rocket science, but instead just a few easy steps.

Also dont be tempted to dispense with the CDR system. These engines are designed to run with a slight negative pressure in the crankcase.

Unhooking the CDR will eventually allow leaks to start and the engine to become a sloppy mess.

Just some thoughts.

Missy

 

[dangerousdave]

This should be added to the Stickies.
Thanx AGAIN, Robyn.

 

[Missy Good Wench]

Your welcome.

Building a 6.5 is not a hard task, but rather one that takes a little finesse to make it a great job.

I am a builder that takes extra time and patience to do the simple tasks.
Extremely anal about neatness.

I absolutely hate hashy looking jobs.

Some factory stuff is a bit tacky in as much as the stuff breaks or is impossible to replace in short order after the rigs gets a few years under its belt.

Example, the clips that hold the +++ cable that runs across the top of the fan shroud.

These break and the GM store either cant get them or they are $$$$$$$$$$$$$$.

I found a great little replacement that looks right smart and is cheap.

I will take some pictures and write a post on it.

My goal is to fix that which the factory did a poor job on and to also make the total rebuild look as near a factory install as possible.

Clean, sanitary and functional.

When growing up and learning from my dad, there were many times that I got the "Old Mans" lecture on taking time to do it right or do it over.

The extra time spent tending to details pays off many times over.

My number one rule is, "Check it twice" then "check it again" then before you bolt the pan on check it one last time just to be sure you did it right.

The little things are what make the first startup that goes so well a real pleasureable time.

Starting DaHoooley for the first time was just like I had left the truck from a run in the night before.

Just hope to add more goodies to the list of things that can help others make their creation come alive and reward them with success.

There is so many little things that I rarely think about.
During the build this time, I was trying to take as many pix as possible of the many areas that there are so many questions about.

I wanted to do a series on disassembly and such on the GMx turbo but mine was Ok so I did not take it apart.

The turbo is an easy little critter to work on. maybe I can find one and do a post on this subject.

Later troops and thanks.


MGW

 

[bison]

I prefer just RTV on the pan rail,I aint sold on the aftermarket pan gaskets as they keep the rear rubber strip that comes with and is the same size as OEM,from compressing enough to keep a good seal + the bolts will have a tendency to come loose as the gasket settles over time.same goes for the valve covers.

I also prefer 3 wraps of teflon tape on the head bolts(or studs)and the long waterpump bolts over tread sealer as to much of the latter can get between the gasket and can cause grief later.

My 2c

 

[Missy Good Wench]

The new Felpro pan set is very good.
The gasket is not like the early cork stuff. Its a very dense gray material and goes all the way around the front cover unbroken. The older sets had the gaskets 4 pieces.
Rear rubber strap
Side rails LH and RH
short front piece.

Real POS

The new ones are super and will likely seal better for a longer period of time than even the silicone goop.

Niow the Vc's are not even a go with a gasket.

MGW

 

[Matt Bachand]

I used permatex Right Stuff on the rails and front, and the rubber seal with permatex under it, above it, and heavy in the corners.

Even though I had the felpro gasket (wanted the rear rubber) I chose the permatex instead.

No leaks.

Factory pan had a silicone also. No gasket.

 

[bison]

IMO,gaskets are fine with a cast pan,but pressed steel pans like we have on the 6.5 are to flexable and distort easely.
cork gaskets are no good I agree,but the 1 piece felpro dont fare much better,now one has 2 surfaces to seal off,top and bottom of the gasket.

Feel free to use whatever,but I would stick with RTV.It may be a pain to get the pan off, but that shows the exellent seal it makes.

 

[Missy Good Wench]

Been through a buttload of these little diesel creatures and the pan has never been an issue.

Then VC's only seem to stay leak free with the goop in a tube.

Pan is as good as any BBC or SBC but the Vc's are crap.

MGW

 

[matuva]

Dont be tempted to use gaskets on the Valve covers. They will leak, ask me how I know this. ---

I know how you know

 

[TurboTahoe]

Excellent write-up Missy! Thanks so much!

-Rob

 

[Missy Good Wench]

The intent is to give a good guidline for those who have a need for some guidance.

There are always different or alternative methods but the way I have described work and work well.

I just try to keep up a high level of accuracy and good reliable techniques that can work for anyone.

Thanks
Missy