Rear piston appears slightly melted. What to do about it?

So I started getting antifreeze in my oil. Here's the thread on that: http://www.steelsoldiers.com/showth...-Small-amount-of-antifreeze-in-oil&highlight=

I finally got time to start working on it, and got the rear head pulled today. I should have the front one off tomorrow. It has the old style tabbed head gaskets on it. I haven't found a definite source for the antifreeze leak, but I did find another issue...
It appears the rear piston is slightly melted along the rear edge, and there's a few pits on the face. There's a bit of melted aluminum spatter on the face of the piston along the rear edge, and a bit on the liner above that, above where the piston rides. The portion of the liner I can see, and the face of the head/valves don't appear to have any damage.

The exhaust port of that cylinder has a lot of oil residue/sludge in it, and a portion of the exhaust manifold gasket was missing which blew oil down the side of the block. I'm guessing there's oil leaking into the exhaust port from around the valve, so I'll have to work on that.

Could these two things be related?


I'm the 4th person on Steel Soldiers to own this truck. The first owner (BFR) installed a pyro pre-turbo, so hopefully the EGTs haven't been too high since then. The highest I've had the EGTs is 1,200 degrees one time for less than a minute. So it's possible that piston has been like that for 8-10 years, through 4 owners, and ??? miles/hours...

So do y'all think this piston is bad enough that it NEEDS to be replaced? If it's been like that all this time, and the liner is fine, I'm hoping I don't have to replace it. If not, could I just swap in one good used take-out piston? Anyone else encounter this before, and what did you do?




Thanks!

AT the very least, I'd pull it and put new rings on there. If you could find a piston, even better(imho). I'd wait till you get the other head off to worry about doing anything though.

M37M35 said:

So I started getting antifreeze in my oil. Here's the thread on that: http://www.steelsoldiers.com/showth...-Small-amount-of-antifreeze-in-oil&highlight=

I finally got time to start working on it, and got the rear head pulled today. I should have the front one off tomorrow. It has the old style tabbed head gaskets on it. I haven't found a definite source for the antifreeze leak, but I did find another issue...
It appears the rear piston is slightly melted along the rear edge, and there's a few pits on the face. There's a bit of melted aluminum spatter on the face of the piston along the rear edge, and a bit on the liner above that, above where the piston rides. The portion of the liner I can see, and the face of the head/valves don't appear to have any damage.

The exhaust port of that cylinder has a lot of oil residue/sludge in it, and a portion of the exhaust manifold gasket was missing which blew oil down the side of the block. I'm guessing there's oil leaking into the exhaust port from around the valve, so I'll have to work on that.

Could these two things be related?


I'm the 4th person on Steel Soldiers to own this truck. The first owner (BFR) installed a pyro pre-turbo, so hopefully the EGTs haven't been too high since then. The highest I've had the EGTs is 1,200 degrees one time for less than a minute. So it's possible that piston has been like that for 8-10 years, through 4 owners, and ??? miles/hours...

So do y'all think this piston is bad enough that it NEEDS to be replaced? If it's been like that all this time, and the liner is fine, I'm hoping I don't have to replace it. If not, could I just swap in one good used take-out piston? Anyone else encounter this before, and what did you do?

View attachment 662965View attachment 662966View attachment 662967


Thanks!

Click to expand...

Your in the range of melting aluminum @ 1200 Deg. How accurate is your pyro gauge? Is it digital, or analog. If your gauge is just 2% off, you could have exceeded 1220 deg's, and caused the piston melting.

Happened to my truck http://www.steelsoldiers.com/showthread.php?144215-LDT-465-1C-engine-noise&highlight=
I had the same thing happen on a truck I bought. It ran fine just had a knock.
I put in a new liner and piston I got from white owl.
Bypassing the FDC and not cutting the fuel back
could cause this on one or more cylinders if EGT in not monitored

I'd replace the piston to avoid any future issues. You already have the engine partially apart.

It would also be a good time to check bearing clearance
and put in new rod bolts.

jbayer said:

Your in the range of melting aluminum @ 1200 Deg. How accurate is your pyro gauge? Is it digital, or analog. If your gauge is just 2% off, you could have exceeded 1220 deg's, and caused the piston melting.

Click to expand...

EHHH its an alloy, not 100% aluminium. I've run 1200 for years and when I did head gaskets, there was no issues. I'd imagine it was there before he got it.

I got the other head pulled yesterday and the other pistons are fine. The head gaskets didn't seem to show any obvious signs of leaking compression or antifreeze, so I still don't know for sure how the antifreeze got into the oil.

The only other issues I've found so far is the #6 exhaust valve leaking oil into the manifold, and the #6 exhaust manifold gasket blown out. I don't know if any of these things could be related...

gimpyrobb said:

AT the very least, I'd pull it and put new rings on there. If you could find a piston, even better(imho). I'd wait till you get the other head off to worry about doing anything though.

Click to expand...

I turned the engine until the piston was at the bottom and the liner looks fine. There's no scoring and the cross-hatch hone marks are still visible. That being the case, why do you suggest replacing the rings even without replacing the piston?

jbayer said:

Your in the range of melting aluminum @ 1200 Deg. How accurate is your pyro gauge? Is it digital, or analog. If your gauge is just 2% off, you could have exceeded 1220 deg's, and caused the piston melting.

Click to expand...

It seems to be pretty accurate, but I don't have a way to verify it precisely. It's an analog Isspro gauge. From what I've read, 1,200* should be safe, as Gimpyrobb explained below.

jacklegjim said:

Happened to my truck http://www.steelsoldiers.com/showthread.php?144215-LDT-465-1C-engine-noise&highlight=
I had the same thing happen on a truck I bought. It ran fine just had a knock.
I put in a new liner and piston I got from white owl.
Bypassing the FDC and not cutting the fuel back
could cause this on one or more cylinders if EGT in not monitored

Click to expand...

That one is much worse than mine! Mine ran great except for getting antifreeze in the oil somehow. I wonder what it is about #6 having issues?

jacklegjim said:

It would also be a good time to check bearing clearance
and put in new rod bolts.

Click to expand...

I've read about the rod bolt issues. Is there a source for good rod bolts? Does ARP make any bolts/studs that fit?

gimpyrobb said:

EHHH its an alloy, not 100% aluminium. I've run 1200 for years and when I did head gaskets, there was no issues. I'd imagine it was there before he got it.

Click to expand...

This is my understanding. I've also seen where people have ran 1,300*+ supposedly without issues, but I'm not going to go beyond 1,200*. I'm pretty sure this piston has been like this for awhile.

http://www.agkits.com/hercules-478-diesel-connecting-rod-bolt-40-1091706.aspx#.WIVf3FROLCQI
This is the rod bolts I used.
The price shown is for one.

I actually said at the least I'd change the rings, I think swapping out the piston would be better. The rings are what touch the cyl wall and keep the compression in check, that was my reasoning.

I wouldn't worry about the integrity of the piston, but I would feel better knowing the rings hadn't lost some tension.

I wonder if you would benefit from making a leak-down tester?
Jjust a plate of plexi or anything flat, punch a couple holes so you can bolt it down (use an o-ring to seal) and add a central hole for an air fitting. Put a flowmeter and pressure regulator on it to see what the rate is, compare this to a couple other cylinders... if it's about the same I'd call it good.

teletech said:

I wouldn't worry about the integrity of the piston, but I would feel better knowing the rings hadn't lost some tension.

I wonder if you would benefit from making a leak-down tester?
Jjust a plate of plexi or anything flat, punch a couple holes so you can bolt it down (use an o-ring to seal) and add a central hole for an air fitting. Put a flowmeter and pressure regulator on it to see what the rate is, compare this to a couple other cylinders... if it's about the same I'd call it good.

Click to expand...

You would need something stronger then PlexiGlass to hold the proper pressure needed. The factory leak-down detector used the injector hole and about 150 PSI .

Sorry, I was thinking about the big drops of 1/2"-1" plexi I had sitting around (actually, I think it's mostly lexan) when I suggested that material.
Aluminum or steel plate is probably more common in people's scrap piles... from, say the center drops out of MRAP wheel adapters.

rustystud said:

You would need something stronger then PlexiGlass to hold the proper pressure needed. The factory leak-down detector used the injector hole and about 150 PSI .

Click to expand...

Highly recommend pulling out the piston and checking it and the rings. Some of the metal that melted might have blown down around and behind the top compression ring which could cause it to not seal properly. I agree that it is best to put in another piston and rings so you are not always thinking "Will it be a problem? I wish while I was there I had replaced it so I was sure it would be OK for a long time". Being the cautious sort if I know of anything marginal on a truck or other machine I want to depend on I like to know all is as good as it can be, given normal wear or it will bug me. I do not always want that lingering thought of it possibly going wrong again because I did not take the time to fix it right when I had a good chance. It is called peace of mind; I like that!.

Further thoughts, sorry I cannot relate the multifuel engine models but we have noted some blocks do not have a coolant passage at the rear of the block and others do. When running engines in containers, using a temp checking gun as it warmed up around the heads and block we noted differences. On engines without the cooling passage at the rear we found that area gets hot faster than the rest of the block. So, this is a good reason to let any engine warm up and normalize a bit before taking off under high load conditions. This hotter area until all normalizes also can cause gasket failure out the back of the block.

M543A2 said:

Further thoughts, sorry I cannot relate the multifuel engine models but we have noted some blocks do not have a coolant passage at the rear of the block and others do. When running engines in containers, using a temp checking gun as it warmed up around the heads and block we noted differences. On engines without the cooling passage at the rear we found that area gets hot faster than the rest of the block. So, this is a good reason to let any engine warm up and normalize a bit before taking off under high load conditions. This hotter area until all normalizes also can cause gasket failure out the back of the block.

Click to expand...

I've heard of that from "Tracey Varns" the tractor racer. He mentioned that certain blocks where "weaker" in the back then others. I cannot remember if this was from the factory drilling out the passages or not. I have seen blocks loose large sections of the rear though.

i find inline 6s are usually hot on the back cylinder compared to the other 5, bmw gassers are not immune either, i punched the back freeze plug out of my 12v cummins and installed a kit that is plate with a fitting that you tee into the heater hose, helps cool down #6 for what its worth

gimpyrobb said:

I actually said at the least I'd change the rings, I think swapping out the piston would be better. The rings are what touch the cyl wall and keep the compression in check, that was my reasoning.

Click to expand...

I agree swapping the piston would be better. What I was trying to ask is, why do you think the rings might have an issue? Too much heat? The liner doesn't show any damage.
If I pull the piston and carefully check the rings and they appear okay, would it be a bad idea to put the original rings on the new piston EXACTLY as they came off? Reason being they're already broken in to that position in that liner. Obviously, if the rings are compromised at all I wouldn't want to do that. But at this point, the only known issue with that cylinder is the slightly melted piston.
The engine didn't seem to have any excessive blow-by. If the rings could be damaged due to heat, I wouldn't want to reuse them. But the piston doesn't seem to have gotten THAT hot...

rustystud said:

I've heard of that from "Terry" the tractor racer. He mentioned that certain blocks where "weaker" in the back then others. I cannot remember if this was from the factory drilling out the passages or not. I have seen blocks loose large sections of the rear though.

Click to expand...

winfred said:

i find inline 6s are usually hot on the back cylinder compared to the other 5, bmw gassers are not immune either, i punched the back freeze plug out of my 12v cummins and installed a kit that is plate with a fitting that you tee into the heater hose, helps cool down #6 for what its worth

Click to expand...

That's an interesting idea... Do you have a link to that kit?

M543A2 said:

Further thoughts, sorry I cannot relate the multifuel engine models but we have noted some blocks do not have a coolant passage at the rear of the block and others do. When running engines in containers, using a temp checking gun as it warmed up around the heads and block we noted differences. On engines without the cooling passage at the rear we found that area gets hot faster than the rest of the block. So, this is a good reason to let any engine warm up and normalize a bit before taking off under high load conditions. This hotter area until all normalizes also can cause gasket failure out the back of the block.

Click to expand...

There must be something to this... It seems like #6 is the most likely one to have issues.

Oh, and I have a couple take-out pistons coming from Searls84. Thank you!

jacklegjim said:

http://www.agkits.com/hercules-478-diesel-connecting-rod-bolt-40-1091706.aspx#.WIVf3FROLCQI
This is the rod bolts I used.
The price shown is for one.

Click to expand...

Thanks! They're awful proud of those! I wonder if ARP has ones that would work for a comparable or better price. I may contact them about it...

cant find the exact one i got years ago but this is the plate that is the root of the kit a popular auction site has various kits but link posting is frowned upon