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1988 Case 7120 - excessive blow by

A

Anonymous-0

Well-known Member
I have foolish interest in looking at a "mechanics special". Dealer tells me it has "excessive blow by". From what I researched, the two likely cuplrits are a leaking turbrocharger or the rings. So would have to invest 1,500 in cylinder kit and 500 in a new turbo. If I could somehow troubleshoot the problem, rather than just fix those two items in hopes that it solves the issue, then I would be much wiser.

How do you fellas assess a Cummins Diesel with blow by?

From the reviews I have read, the Case IH 7120 is an amazing tractor choice, so that is why I am toying with the idea.
 
Thanks for the reply. I have read that the early models(87,88,89) did have have a problem with the "ring lands" and compression rings. Would a compression test identify if the rings are at fault?

I have put cylinder kits in a Farmall M's before. Would this be a similar task, just much heavier?
 
edit to my above comment. I should have clarified, broken ring lands, would be referring to the piston having a portion broke off. Where does that broken piece go? Either it gets hammered by a valve and pushed out if small enough, or it stays in there and bounces around. Either way, if a ring land is broken, there is cylinder scoring, which will require a new sleeve, and if the valve hit it, then the valves will need replaced in the head. I can only imagine that maybe there is a cylinder that has significant damage. But does a damaged cylinder affect the rest of the engine? Can a fella count on fixing that cylinder, because the rest of the engine is likely not broken, or otherwise damaged from it?
 
I have fixed a ton of those, usually the pieces will work their way up to the top and bang around on the valves. And those valves don't have much meat for grinding anyway, if it has alot of hrs they probably will need replaced anyway, install pistons and sleeves, rod and mains
 
Appreciate the input. They sell kits that contain: Pistons, Rings, Sleeves, Rod Bearings, Main Bearing Set, Head Gasket Set, Oil Pan Gasket.

When I did my Farmall M, I did not install the Main bearings, because I did an in-frame rebuild. Did all else though. Can you in-frame install the Main Bearings? If not, is there any harm done in skipping that.
 
I have a 89' 7130 on the farm and last year it developed excessive blowby. To make a long story short i found out after some investigation that the early model 7130's had a different injector that had problems and i had the injector tip blow up and torched a hole threw the piston. What i don't understand is why isn't the dealer that is selling the tractor fixing the problem as they get all there parts for wholesale and then he can advertise the tractor as a fresh rebuild and add to the value substantially.
 
Well, it sounds like a fella would have to count on buying the cylinder kit, and maybe some injectors. 10,500 is alot of hours.
 
(quoted from post at 15:38:33 03/09/13) Well, it sounds like a fella would have to count on buying the cylinder kit, and maybe some injectors. 10,500 is alot of hours.
Click to expand...

My 8920 has 6K and some blowby and uses a little oil ~1 gallon in 2-3 days working hard. Head shop guy told me the engine is in great shape and just needs valves reset, did that. Sent injectors in for a rebuild (to a performance shop) got a little bit of a power boost on them, added fuel and a better set of wheels on the turbo. Next I bent the shaft on the 250 hp pto dyno and before I was pushing ~180-190hp.

These tractors can do some serious work when built right but are a solid work horse out of the box. I dont recommend adding alot of fuel with out a better flowing turbo for lower egt's. My egt's are actually slightly lower that before the valve job and 180-190hp dyno. I have mechanical gauges for EGT, boost, oil pres, coolant temp, oil temp, and fuel pressure (very informative, the bar gauges are junk imo)
 
What are egt's? And yeah, I have read that though advertised as
150 at the drawbar, people often say they put their 7120 on a
dyno and see them commonly much above 150.
 
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