MoS2 and Pistons

[KCJeep]

I know how MoS2 is supposed to work. And I believe it does what they say it does because I've actually used it. But, curious, does anyone know if MoS2 will bond to aluminum piston skirts and/or the cylinder walls? I understand it is supposed to plate metal bearings and such but I wondered if aluminum pistons were different.

My model Jeep has been plagued with piston skirt issues in the past and I was curious if MoS2 would slick 'em up. I've used in it the Jeep before and did get a slight mileage boost and quieter running, however my one UOA with it in the crank showed fairly high aluminum. One done later without it did not. However the oil in the UOA turned out to be a 5w20 (long story) and old Jeep 4.0 pistons do NOT like 5w20's. The later UOA was a 10w40 so I imagine that's why the aluminum came down so much.

Just curious, thanks!

P.S. I am not asking whether or not I should use it, whether or not you like additives all that other blather please save just curious about the aluminum and MoS2 or any pertinent discussion to that please.

 

[123Saab]

Have you considered trying Ceratec?

http://www.bobistheoilguy.com/forums/ubb...C_d#Post3007366

I just Dropped a can of that in Our 08 Jeep Liberty with the corporate 3.7L.

As my Wife puts more miles on it I will add to my post here:

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3389976/I_bought_some_Ceratec#Post3389976

 

[SwampSurvivor]

I would think the high aluminum would be caused by the 5w-20.

When my 2000 tosses a piston skirt, I'm going to find a 99 or older engine and put a 0331TUPY head on.

 

[jeepman3071]

Originally Posted By: Miller88
I would think the high aluminum would be caused by the 5w-20.

When my 2000 tosses a piston skirt, I'm going to find a 99 or older engine and put a 0331TUPY head on.


The piston skirt issues have happened on anywhere from '93, to '96-'02 models. I think it is more of an issue of the bores allowing too much piston slap combined with weaker piston castings in some batches. Some engines are fine, others aren't. I've seen a few 2000 and 2001s with 200k+ miles and they run perfectly fine.

The particular 1993 I mentioned was on a friend's dad's Cherokee. It was a 1993 Country edition. Bright red and meticulously taken care of. It had something like 100k on it when the #3 piston grenaded. Luckily there was no other damage and he replaced the one piston and drove it for another 100k or so.

As far as the MoS2, I'm interested as well. I will say I have run it a few times and didn't notice anything good or bad. My engine was just as noisy as before, and I had no change in mpg. It may have helped, but not enough for me to notice.

 

[440Magnum]

I think you've conclusively proven that adequate viscosity for a 4.0 is far more effective than additives.

Do what most other 4.0 owners do: run T6 or equivalent, drive 300,000 miles, and enjoy.

 

[440Magnum]

Originally Posted By: jeepman3071
Originally Posted By: Miller88
I would think the high aluminum would be caused by the 5w-20.

When my 2000 tosses a piston skirt, I'm going to find a 99 or older engine and put a 0331TUPY head on.


The piston skirt issues have happened on anywhere from '93, to '96-'02 models. I think it is more of an issue of the bores allowing too much piston slap combined with weaker piston castings in some batches.


I agree- lubrication has ZERO to do with cracked piston skirts on any engine, unless its from seizing in the bore (and that doesn't happen on 4.0s) Also I think it is greatly aggravated with too much time at high RPM- "high" in this case being anything over 3500 or so. The 4.0 doesn't like to wind up for many reasons (stroke, limited breathing, cam, stroke/rod ratio) I tend to think that automatic-transmission equipped XJ's, WJ's, and ZJ's in particular spend way too much time in the upper RPM bands. Its far better to lug the snot out of a 4.0- its no faster when you rev it up anyway. When I was daily driving the 5-speed 99 XJ that now belongs to my daughter, it was a rare day that I put it above 3500 RPM. The 01 automatic, on the other hand, would sneak up there merging on freeways if I didn't deliberately force an early shift by lifting.

 

[SwampSurvivor]

Even with 31'' tires and auto trans I rarely have managed to get mine in the upper RPM ranges. I have only had it above 4000 a handful of times.

I know nothing has changed in the pistons, but it just seems that the early COP 4.0s are the ones that suffer the most piston skirt failures. Or around here. Everyone I know that has had a 4.0 toss a piston skirt was a 99-01WJ, 00-01XJ or 00-01TJ. I think newer than 2001/2/3 are too new to experience the problem. I discussed with someone on here (Mopar440 I think) - we were wondering that it may be related to the catalysts in the exhaust manifold that back-feeds heat.

Mine has been a bit more chattery from the bottom end. Not a rod knock but doesn't sound like piston skirt failure (much higher pitched). I can't get to the access plate for the flex plate either :S

 

[SwampSurvivor]

Originally Posted By: 440Magnum
Originally Posted By: jeepman3071
Originally Posted By: Miller88
I would think the high aluminum would be caused by the 5w-20.

When my 2000 tosses a piston skirt, I'm going to find a 99 or older engine and put a 0331TUPY head on.


The piston skirt issues have happened on anywhere from '93, to '96-'02 models. I think it is more of an issue of the bores allowing too much piston slap combined with weaker piston castings in some batches.


I agree- lubrication has ZERO to do with cracked piston skirts on any engine, unless its from seizing in the bore (and that doesn't happen on 4.0s) Also I think it is greatly aggravated with too much time at high RPM- "high" in this case being anything over 3500 or so. The 4.0 doesn't like to wind up for many reasons (stroke, limited breathing, cam, stroke/rod ratio) I tend to think that automatic-transmission equipped XJ's, WJ's, and ZJ's in particular spend way too much time in the upper RPM bands. Its far better to lug the snot out of a 4.0- its no faster when you rev it up anyway. When I was daily driving the 5-speed 99 XJ that now belongs to my daughter, it was a rare day that I put it above 3500 RPM. The 01 automatic, on the other hand, would sneak up there merging on freeways if I didn't deliberately force an early shift by lifting.




If your daughter sells it ... I know someone who would be willing to pay shipping to NY

A texas 5 speed Cherokee.

Of course that's a few years off though.

We'll see what my situation is when mine drops a skirt. If I have a place to work, I may just buy another $500 Cherokee with a good engine (they rust to death) and swap engines.

 

[440Magnum]

Originally Posted By: Miller88



If your daughter sells it ... I know someone who would be willing to pay shipping to NY

A texas 5 speed Cherokee.


Yeah, good luck with that. She won't hardly let me near it anymore, let alone sell it. I even asked if she was thinking about another car when she graduates college and if me kicking in half would be a good graduation present, and she wasn't interested at all. She loves that little machine to death.

 

[SwampSurvivor]

Hopefully in the next few years I can fly/drive to a nicer area and buy one to drive back to NY.

That one will not be used in the winter or off road. Don't know why , but Cherokees are my favorite Jeep vehicle. And that's after growing up in Wranglers/CJ.

 

[andyd]

What happens? Do the skirts break off ?

 

[KCJeep]

Many great points here guys, thanks! Ceratec is just too pricey for me to bite, in fact the 8 bucks a bottle is why I quit using MoS2. Pondering going back to it though...and will be sticking with PYB from here on out with the Jeep once this last Castrol OCI is over. Done testing in it, Pennzoil for the win!

 

[SwampSurvivor]

Originally Posted By: andyd
What happens? Do the skirts break off ?


Yup. They just shatter. Usually after extended high RIM operation.

 

[KCJeep]

I have never heard the high RPM theory before, and I've read up on the issue a lot. Probably too much it's got me paranoid ha ha.

If it's true my Jeep is in good shape, I rarely get near 3k.

 

[GregGA]

I've read all the threads on MoS2, and I just added a can to my 87 XJ 4.0. I'll report my findings.

Regarding RPM. I've had my Jeep since new. It has 129,000 on it and is my "baby". I've added a bigger throttle body, 4 hole injectors, 4.56 gears, and opened up the exhaust. It flat out scoots. While I don't cruise over 3500 RPM, it will pull strongly up to as fast as I want to go in 3rd,5000 RPM. Here's hoping AMC's metallurgist's were at the top of their game