Duramax Diesels Forum Truck of the Week
  #766  
Old 11-16-2018, 01:31 PM
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ah 10-4
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  #767  
Old 11-16-2018, 04:51 PM
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I have little to no experience with the TCB coating. All Gold coat. I have never seen Gold after it left my shop and have not seen any failure personally. I'll drop a call to Swain on Monday. IIRC Dirty Hooker coated a lot with Gold. Wonder what they have seen.

One issue with the cast is they are susceptible to water pitting, and this looks similar, but doesn't make sense to me. I think that the pistons should have some sort of coating in this application to, if nothing else, help with the water pitting issue. However, if it doesn't stick.....
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'04.5 EC/LB 4x4.
Howard Rods w/ oiler hole.
Oval Chambers and valve reliefs cut in Mahle Cast Pistons. 17.5:1
SoCal Stage 2 heads, 3388 Cam, Billet Flywheel, and harmonic balancer.
Danville 68mm VVT Turbo
100 over injectors.
PPE Dual CP3s
ProFab Castflow headers and uppipes.
100 PSIA MAP Sensor
Kennedy dual lift pump.

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  #768  
Old 11-16-2018, 07:48 PM
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Thanks for the help Jon. I really thought this TBC would give us the added protection needed for extended high temp operation.

Recall when I spoke with Swain about the two coating options, this was the best compound for long term heat dissipation. The gold is geared more towards absorbing a thermal shock of nitrous, and wasn't recommended coating for this build.

As for your water question, it's entirely possible some condensation from the charge cooler blows through the cylinders on the decel, when charge air is still hot but boost it off. Mark and I witnessed those exhaust manifolds make enough water at idle to fool us into thinking we had a leak. We even looked into the intake to be certain the charge cooler wasn't leaking. That side was dry. But this issue only showed up on second engine when the seawater temp was sub 40F, and cleared once we got some big heat in the systems. So yes the pistons are likely to see some moisture.
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  #769  
Old 11-17-2018, 12:10 AM
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Popped the other head off, and more of the same. However a strange coincidence, cylinder #1 which had a pressure probe in it rather than a glow plug delete stick, and a EGT probe in the exhaust port, has the least amount of coating damage. Go figure..

The lifted coating patterns appear very random, and show no specific pattern across any two pistons. If water intrusion started the issue, one might expect to see a pattern around the valves or such. Doesn't appear to be so.

Next, pull the pistons and inspect the other surfaces..
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  #770  
Old 11-17-2018, 01:03 AM
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I say hit it with some high temp BBQ paint. That should do it
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  #771  
Old 11-17-2018, 05:10 AM
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I have not noticed any pattern to the water pitting on the pistons. And to be clear, I think it is water intrusion based on the pistons that I have seen.

That last set of pictures shows clearly that the coating is bubbling and peeling. An adhesion issue. Chance there is a contaminate in the metal that is coming out under load.
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But.....What do I know.

'04.5 EC/LB 4x4.
Howard Rods w/ oiler hole.
Oval Chambers and valve reliefs cut in Mahle Cast Pistons. 17.5:1
SoCal Stage 2 heads, 3388 Cam, Billet Flywheel, and harmonic balancer.
Danville 68mm VVT Turbo
100 over injectors.
PPE Dual CP3s
ProFab Castflow headers and uppipes.
100 PSIA MAP Sensor
Kennedy dual lift pump.

Dynoed 690 HP / 1200 TQ
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  #772  
Old 11-17-2018, 11:48 AM
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Quote:
Originally Posted by Fingers View Post
I have not noticed any pattern to the water pitting on the pistons. And to be clear, I think it is water intrusion based on the pistons that I have seen.
Looks something like the examples below?? Made me dig up pics from 2010. My first cracked Duramax pistons.. Ah the memories...

Back then I thought it was just due to 1800F EGT for extended periods. But if you look closely at the cylinder wall you can see the etching of a water line where it laid in there.

That's from my LLY in the OG PPE boat. I first wrote if off to being a junkyard motor, but we later learned this was from charge cooler condensation drain back after shutdown. We replaced those with a first off the press Mahle race cast set, polished bowl. Also relocated the charge cooler to stop it from happening.

This Banks intake uses an upflow design, so any condensation on shutdwon drains into the turbo feed rather than down the intake runners. However we also have to take into account reverb on the exhaust sucking condensation from the manifolds back into the cylinders at idle..
Attached Images
File Type: jpg cracked-piston-2.JPG (89.0 KB, 56 views)
File Type: jpg piston-2.JPG (180.5 KB, 59 views)
File Type: jpg piston-burnt-2.jpg (136.5 KB, 58 views)
File Type: jpg dm-piston.jpg (125.7 KB, 57 views)
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  #773  
Old 11-17-2018, 12:14 PM
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Quote:
Originally Posted by 2004LB7 View Post
I say hit it with some high temp BBQ paint. That should do it
I was thinking header paint, but....
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  #774  
Old 11-17-2018, 06:09 PM
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The failures of the pistons are because of an unrecognized stress. I don't think the pitting has any effect on the longevity of them. Though I have seen them eroded down significantly.
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But.....What do I know.

'04.5 EC/LB 4x4.
Howard Rods w/ oiler hole.
Oval Chambers and valve reliefs cut in Mahle Cast Pistons. 17.5:1
SoCal Stage 2 heads, 3388 Cam, Billet Flywheel, and harmonic balancer.
Danville 68mm VVT Turbo
100 over injectors.
PPE Dual CP3s
ProFab Castflow headers and uppipes.
100 PSIA MAP Sensor
Kennedy dual lift pump.

Dynoed 690 HP / 1200 TQ
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  #775  
Old 11-17-2018, 07:34 PM
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I concur. My failures were unrelated to the pitting. Sure looks nasty however.

So what's your thoughts on polishing the tops?
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  #776  
Old 11-18-2018, 06:42 AM
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Polished or rough, same result as far as pitting.
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But.....What do I know.

'04.5 EC/LB 4x4.
Howard Rods w/ oiler hole.
Oval Chambers and valve reliefs cut in Mahle Cast Pistons. 17.5:1
SoCal Stage 2 heads, 3388 Cam, Billet Flywheel, and harmonic balancer.
Danville 68mm VVT Turbo
100 over injectors.
PPE Dual CP3s
ProFab Castflow headers and uppipes.
100 PSIA MAP Sensor
Kennedy dual lift pump.

Dynoed 690 HP / 1200 TQ
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  #777  
Old 11-18-2018, 09:39 AM
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What about nickel plating it, or hard chrome?
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2006 BRM Jetta TDI. Injectors, turbo, Malone custom tuning on ecm and tcm
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  #778  
Old 11-18-2018, 10:16 AM
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Adhesion is always the issue. Especially with high silica alloys.

In the case of the coating failure you have seen. There appears to be something bubbling up from underneath. Might have to vacuum bake them prior to coating to remove impurities.
__________________
But.....What do I know.

'04.5 EC/LB 4x4.
Howard Rods w/ oiler hole.
Oval Chambers and valve reliefs cut in Mahle Cast Pistons. 17.5:1
SoCal Stage 2 heads, 3388 Cam, Billet Flywheel, and harmonic balancer.
Danville 68mm VVT Turbo
100 over injectors.
PPE Dual CP3s
ProFab Castflow headers and uppipes.
100 PSIA MAP Sensor
Kennedy dual lift pump.

Dynoed 690 HP / 1200 TQ
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  #779  
Old 11-18-2018, 12:37 PM
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Anyway to test these adhesion theories outside my customers two very expensive engines?

I'll have the second engine back home Tuesday. While it has less run time, we know it saw higher heat and cyl pressure than this one. Should be interesting to compare since all 16 pistons are from same bake.
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  #780  
Old 11-18-2018, 01:13 PM
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The only one I'm familiar with that may work is ASTM D3359. But I dont think it would work for that coating, being fairly soft
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285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

2006 BRM Jetta TDI. Injectors, turbo, Malone custom tuning on ecm and tcm
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