Melted piston on cummins

[jakecorn]

The number 4 piston on my 1990 Cummins diesel melted down. It also scored the cylinder walls on the adjoining cylinders. When we were driving it we heard a noise, the temp gauge started to climb, when we pulled over it died and wouldn't restart.



I have bigger injectors, pump turned up, the smokey pin, 12 cm exhaust housing, and 3 inch straight exhaust. The exhaust temp gauge never got over 1000 degrees but it seemed like the truck was lugging a lot more than it should have. I was only pulling a trailer weighing about 6,000 gross lbs. It also was running on the warm side of the gauge.



Any ideas what might have caused this. I am going to have all the injectors checked out. The turbo is damaged now, but not sure if that was before or after it blow up. The truck, besides being short on power wasn't missing or smoking excessively.



Any ideas would be appreciated. Also, this truck has over 400,000 miles on it--but I don't think this is a fatigue issue, or is it?





Thanks,



Jason

 

[Paychk]

Sounds like one of the injectors was dribbling fuel into a cylinder and smoked it? The pop test will show if this is the case, you'll want to number the injectors as you pull them to keep them straight. Any one else with a better idea?

 

[phillips5]

Yes it sounds like injector at falt or could be pluged piston cooling nozzles if these engines have them.

 

[Grey Wolf]

I would say yes to the injectors and with that many miles the cooling nozzles too!

 

[bgilbert]

What are your 'bigger injectors'? 1000* pre or post turbo? 12cm housing and you were towing/>???? Time to ditch that egt housing and get something bigger, 14,16cm maybe. With a turned up pump, bigger injectors, 12cm housing, non-intercooled, I bet you've had some high EGT's. I sure hope you've added an intercooler down the lines or your combo is not good for towing. I know with my setup nonIC'd stock turbo-18cm housing empty I can get some high egt's. Was you pulling a long hill in OD? Aluminum melts at like 1270ish*- someone help me here. Lug the engine for more than a few and you're looking at meltdown.

 

[Grey Wolf]

bgilbert,



How about this article



FEATURED ARTICLE: The Importance of E. G. T. and Boost in Turbo Diesel Engines

by: STC Performance Truck and RV

In today's world of high performance, technology changes at a lightning pace an most people that are new to the performance world hear alot of terms and words but have no idea of what they mean. In this article we will try to explain to you in laymans terms what EGT and boost mean and why you need guages to moniter them, how boost affects EGT (exhaust gas temperature) and why it is important to you if you want to keep from having a meltdown inside your diesel engine.



Diesels have aluminum pistons, which have a melting point of approx. 1350 degrees. If your EGT exceeds 1350 degrees for too long, you will melt the pistons in your engine. The exhaust gas temperature (EGT) is measured by a thermocouple that is usually installed in the exhaust manifold before the turbocharger. The thermocouple will register the termperature of the exhaust on the pyrometer guage.



Without a pyrometer in a turbocharged diesel engine, you have no indication of what kind of damage is being done to your expensive engine. Water temperature can't be used as a guideline because it could be measured at only 190 degrees while your EGT is over 1400. EGT's rise very quickly with altitude or a loss of boost, possibly damaging your engine before you see a change in water temperature.



Turbo boost is simply compressed air, which is produced by the turbocharger and forced through an air charge cooler and then into the intake manifold to be delivered to the combustion chamber. Without boost you would have a lot less horsepower. It takes a tremendous amount of exygen to burn diesel fuel completely.



Every turbocharged engine, whether its gasoline or diesel should have a manifold pressure guage or turbo boost guage. This is an important guage in the insurument panel because it lets you know how much power your using and it also lets you know that the engine is getting the proper amount of oxygen from the turbocharger. If there is a leak in the system, the compressed air being produced by the turbo will be vented into the atmosphere and your EGT's will rise very fast.



The boost and pyrometer guages are also great as diagnostic tools. If you are driving and your pyro and boost are both high than you can back off the throttle a small amount which should bring them both down. If your boost is low and the pyrometer guage is running high, you should down shift if your rpm is not too high. If this doesn't help than you have a boost leak. If the boost and pyrometer are low and you seem to have less than normal power than there is a fuel restriction , low fuel pressure or other problem.



Try to remember this: It takes fuel to make turbo boost and it takes boost to control the exhaust gas temperature. Having a guage for reading boost and EGT's can save you a lot of problems and if you do have a problem, it can save you a lot in diagnostics. TIP: If you let the pyro cool to 300 degrees before shutting down, you can extend the life of your turbo dramatically.



STC PERFORMANCE TRUCK & RV

12464 McCANN DR.

SANTA FE SPRINGS, CA 90670

562-944-3694

www.performancetruckandrv.com

 

[dpuckett]

good find, Grey Wolf.



I agree with Bill; the 12cm is no good for towing, esp in a nonIC 1st Gen. I had a 12 on mine with my stock flow EDMs, and some mild pump tweaks. Hit 40+ psi, but EGTs got high almost as quick. And that was empty. I put the 18cm housing back on, did some mild porting, and have dropped boost pressures across the board, but EGTs arent any higher, either at cruise or full throttle. Boost is just resistance to flow, so more boost isnt always better. You have to figure in drive pressure and turbo efficiency maps.



Daniel

 

[Paychk]

Good catch on the oil cooling nozzles, I forgot about those... . Thanks!

 

[1stgen4evr]

fatigue over 400k

I would say that the 400k is not a factor. More likely an injector and the end result of that.



Don't try to "patch it" and get by. You will never be satisfied. Before you put it back in service, be sure you have the gages and such to monitor you boost mods.



James

 

[Old Smoky]

What kind of oil filter are you using?



Mike

 

[BushWakr - RIP]

Did you take a close look at what was left of the piston top??? How about the other piston tops... . do you see a generally dark piston top with grey shadow areas???

Those areas are the result of the injector spray pattern.

Concentrated areas of staining/damage indicate nozzle problems...

Also run your ginger under the edge of the piston bowl rim... do you feel any pitting in there... ?? if so you are running far too much heat which will cause that pitting (burning).

'Smoky's question is another good one... .



pastor bob...

 

[bgilbert]

What are you trying to say Mike, a Fram oil filter??

 

[JLEONARD]

run your ginger under the edge

No, Maryann.

 

[BushWakr - RIP]

:-laf :-laf :-laf ... . Doh !!!! ok, that's a 5 hp penalty for being dumb enough to give away my age... let' go with "F"inger...



pastor bob... .

 

[dpuckett]

I vote for Maryann, too. She was the blond, wasnt she?



Pastor, when I last had my head off, examining what was under it, my piston tops were all pretty much evenly black. What does that mean? I had one bad injector, and got new ones before I blew a piston. Though it WOULD be an excuse for marine low comp pistons. Then 370 nozzles, bigger huffer... .....



-DP

 

[Old Smoky]

bgilbert - Cheap oil filter, that is what I was getting at. You may be able to save a few bucks on a oil change by using a cheap filter, but it can really cost you in the long run. I saw two engines failures last summer due to Fram filters. The Cummins techs. I have talked to also advise against using NAPA, even though they are commonly used.



jakecorn - Any updates?



Mike

 

[1stgen4evr]

Napa

430k miles on the 93 and lots of that with NAPA and some cummins filters. 10k mile interval which is about every two months. Anyone know what is supposed to be better/worse with the filters?



James

 

[csnider]

bgilbert - Cheap oil filter, that is what I was getting at. You may be able to save a few bucks on a oil change by using a cheap filter, but it can really cost you in the long run. I saw two engines failures last summer due to Fram filters. The Cummins techs. I have talked to also advise against using NAPA, even though they are commonly used.



jakecorn - Any updates?



Mike

I have a Napa filter that came with my truck... Although I never used it,It's internals look just like the Wix filters I use. . I figured they're the same(?). . Are the Wix filters a bad idea?... .

 

[Paychk]

Once upon a time all of the NAPA filtwers were made by Wix, they even had a Wix P/N with a couple of extra digits at the end. Now the NAPA Gold filters are mfg. by Wix, the standard ones are made by someone else. Wix filters are a quality filter and should provide you with excellent performance.

 

[MrWinkey]

Oil filters are a big deal. I use the K&N oil filters as every review I have seen reported them to be a high quality filter. I sometimes use Wix but I have a hard time going to the store to get the offical "wix" brand. NAPA switches stuff around too much for me to keep up on.



Oil filter study



That guy does it in his spare time out of his house. He runs the Shelby Dodge turbo cars I also run. Nice guy.



Any updates?