New head causing increased exhaust & fuel consumption

Bill in the U.P.

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L4630 GST
Dec 31, 2020
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Michigan
I had a new (not OEM) head installed on my L4630 (2300 hours) a few weeks ago. The old one was cracked and leaking coolant. Since the new head install the tractor seems to be going through fuel much faster. I keep the tractor in my shop building and when I start it and pull it out it leaves such a cloud of blue in the shop that I have to leave the door open for quite awhile before I can go in and do anything. Is there any reason for this that you know of? It seems to me that a new head would result in better operation (less fuel, less exhaust) nor more. I appreciate any ideas you might have about this. Thanks.
 

ctfjr

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did they use the old valves? Is it possible the new head has bigger valves?
 

North Idaho Wolfman

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#1 Your going to need to do a compression test!
 
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woodman55

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How much blow by. I am just wondering if the coolant took out the rings/walls. A compression test will help tell the tale.
 
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007kubotaguy

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As Wolfman said you will want to check the compression. Typically if an engine gets hot enough to crack the head it will take the spring tension out of the piston rings.
 
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sitric

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Very seldom does just doing top end, make a strong engine. I am assuming op didn't touch the bottom, as he didn't mention doing so.
 

Bill in the U.P.

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L4630 GST
Dec 31, 2020
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Very seldom does just doing top end, make a strong engine. I am assuming op didn't touch the bottom, as he didn't mention doing so.
Nothing done except the head replacement. The back cylinder/piston was free of carbon build up, the other three looked "ok." I will get a compression test done asap.
 

IdahoNative

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Kubota B7100D 4x4, non-HST, FEL 1630
Jan 12, 2022
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I had a new (not OEM) head installed on my L4630 (2300 hours) a few weeks ago. The old one was cracked and leaking coolant. Since the new head install the tractor seems to be going through fuel much faster. I keep the tractor in my shop building and when I start it and pull it out it leaves such a cloud of blue in the shop that I have to leave the door open for quite awhile before I can go in and do anything. Is there any reason for this that you know of? It seems to me that a new head would result in better operation (less fuel, less exhaust) nor more. I appreciate any ideas you might have about this. Thanks.
My B7100 did the same thing after I reconditioned the 750D engine. I installed the head shim that came with the gasket set. I removed it. Ran great after that.
 

hagrid

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The back cylinder/piston was free of carbon build up, the other three looked "ok." I will get a compression test done asap.
That's the one that was sipping coolant. Possible zylinder wall damage there.
 
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kubotafreak

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Id pull the valve cover and make sure the head has valve stem seals. Or pull the intake to see if oil is leaking in. All the compression possibilities aside, oil smoke is cracked head, vss, and since it didn't before you can rule out rings.
 

lugbolt

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do a compression test if you have the stuff to do it with

or pull the head back off and inspect the pistons. You said #3 had little to no carbon. That's an indication that #3 is not running properly. With the head off turn the engine over by hand until a #1 piston is at TDC. Measure how far the piston is out of the cylinder. Or down into the cylinder. Then repeat for #2. It should be identical to #1. Then #3. It also should be identical. If one is further down into the cylinder than the others that connecting rod is most likely bent, I suspect from coolant entry into that cylinder due to prior issues. I may be wrong but that is my gut feeling.