B7100: Newbie Replace Head Gasket?

[North Idaho Wolfman]

Hi Folks,

Getting around to ordering parts: Kubota wants ~280 bucks for a piston/ring kit while Kumar bros has the same parts for ~90 bucks.

Has anyone used a Kumar bro's piston / ring set? I know OEM parts are expensive but if people have had good luck with aftermarket, I'll go that route.

I got a top end set and it worked perfectly, and I haven't heard anything bad about the rest of the set.

 

[Apogee]

Unfortunately, I don't know where to point you to. The challenge you're going to have is that most automotive machine shops have "standard" boring bars that are too big for the cylinder diameter in the Kubota blocks. hence, you need to find someplace that has a smaller boring machine. Some of the shops who do motorcycle or outdoor power equipment will have the smaller diameter equipment, but this is a case where you need to let your fingers do the walking.

Almost any decent automotive machine shop will be able to do the work on the head. The big thing is they need to check it for cracks due to the overheating issue. There are several shops in Seattle that are used to doing diesel work that would be worth calling.

I wouldn't hesitate to run the parts from the ebay seller you mentioned. Honestly I'd be very surprised if Kubota even makes their own pistons. They are likely coming from an OEM supplier anyway.

Good luck,

Steve

 

[klipto]

Hi Everyone,

New problem and I could use some advice!

To remind you of the past 3 pages: I thought I had a blown head gasket (which I did) but it turns out, I also had a burnt piston. Since I was in there already, I (i) honed all cylinders and (ii) replaced all pistons and rings. I am getting the injectors cleaned too as it looks like they may have been the source of the burnt piston.

I put all 3 pistons back into the block and as long as I don't tighten down the bolts on the rods, I can turn the crank by hand. However, as soon as I tighten them slightly, I cannot turn the crank anymore. Any ideas why this is happening? Something is not aligned in there and I am jamming up the crank, I suspect, but as I said, the crank spins when the rod's bolts are hand tight / loose.

Any insights appreciated, and as always, thanks for your help!

P.S. Just used the starter to turn it over and that did the trick: I can now turn the crank by hand. I have to now tighten up the bolts to spec, but I am making headway.

Todd

 

[North Idaho Wolfman]

Did you use assembly lube on the main and rod bearings?
If you didn't you could have made the bearings stick and then spinning them dry might have scratched them.
If you haven't put it all together you might want to take a second look at them.

 

[klipto]

Did you use assembly lube on the main and rod bearings?
If you didn't you could have made the bearings stick and then spinning them dry might have scratched them.
If you haven't put it all together you might want to take a second look at them.

Thanks for the advice - I did lube both the main and rod bearings before assembly. I think I just had a bunch of friction from new rings to work through.

 

[Apogee]

Did you put new bearings in it? If so, did you use Plastigage on them to make sure the clearances are correct?

Also, regarding the assembly lube, did you only put it on the side of the bearing that contacts the crank? In other words, did you coat the front and back of the bearings or only the front? The bearing backs should be clean and dry with only the interface between the bearing and crank having lube.

You need to find out where the binding was coming from. If the bearings are too tight you need to figure out why or else you've just wasted a bunch of time. The LAST thing you want is metal shavings in there someplace...

Not trying to make you paranoid, just concerned that you may have spun a bearing using the starter if something didn't have the correct clearance.

Did you buy new bearings for this thing????

Steve

 

[klipto]

Hi Steve,

Ok both you and North Idaho Wolfman convinced me to get back in there and see if I spun a bearing (or worse!). Thanks - I'll update if I did any damage (or if not too!).

I did not replace the bearings as they looked great.

Todd.

 

[Dwarner]

Did you line up the match marks on the rods and bearing caps?

 

[Apogee]

Hey Todd,

Since you're in it this far, I'd STRONGLY recommend stopping by your local auto parts and picking up some plastigage. Check all of the clearances to make sure they're in spec... The bearings can look fine but still have excessive clearance.

If they're not in spec it will affect your oil pressure especially at idle when hot.

IMHO it's worth your time...

Best,

Steve

 

[Apogee]

Two other tidbits:

Dwarner brought a good point about the rod caps. Just in case you don't know, the rod caps are matched to their corresponding rods and they can't be mixed up.

Also, to use plastigage the crank and bearings need to be clean and dry.

Good luck,

Steve

 

[klipto]

Hi - sorry for the sporadic posts here. I had to learn what plastigauge is .

After everyone's suggestions, I tore back into the tractor and measured the clearance on the bearings. They are up to snuff. I did put assembly lube on both sides; so when I button it back up I'll just do the one side (already cleaned off the bearings). Secondly, I did match up the rod caps and had put them in the right way. I think the binding was due to the rod being slightly out of alignment?

In any event, I hope to get some time on the tractor this weekend. Maybe even finish putting it together!

Thanks again for everyone's help. It gives me the confidence to do this, knowing if I run into trouble I can post here. You all are a great resource which helps us newbies learn (by doing and making mistakes, as in my case!).

 

[North Idaho Wolfman]

I did put assembly lube on both sides; so when I button it back up I'll just do the one side (already cleaned off the bearings). Secondly, I did match up the rod caps and had put them in the right way. I think the binding was due to the rod being slightly out of alignment?

The reason they were so tight was because the second coat of lube on the outside had no place to go so it takes up the tolerance, so clean it very well and that will help.
Glad to here you didn't do any damage!

 

[Apogee]

Todd,

One other important tidbit is to remember is everything should be clean enough to eat off off. Cleanliness is super important. Make sure you've also cleaned out the crank passages before reassembling. Any gunk in those passages will end up carving away at the bearings.

Also, DO NOT USE SCOTCH BRIGHT TO CLEAN ANY INTERNAL ENGINE PARTS!!!! It might seem like a great idea but it's not. I can't stress this strongly enough. The Scotchbright fibers can get into stuff and can create a real mess. If you did use it, you really need to be 100% sure that the parts have no fibers left on them. You can always wash the block and parts with Dawn dish soap and water if necessary to make 100% sure everything is spotlessly clean. Better is solvent if you have access to clean stuff but whatever you do just make sure everything is clean, clean, clean... Did I mention stuff needs to be clean????? LOL! Am I being clear here?

As Wolfman advised, make sure all of the assembly lube is cleaned from the back of the bearings and the top and bottom of the rods. I'd recommend using brake parts cleaner to make sure all of the assembly lube is out of there. You want both the bearing backs and the rods to be super clean and dry when you assemble them. Use plenty of assembly lube between the crank and bearings, but never on the back side of the bearings. Also, I'm assuming you Plastigaged after you cleaned both the bearing front and backs right? If not, you need to check it again once the backs and rods have been cleaned and dried. Assuming you did, glad to read things were in spec. As previously mentioned, you want the clearances right because it will affect oil pressure especially when hot so it's worth the time imho.

Rods and cap numbers match and get assembled on the same side when bolting together. Also pistons should have a notch or mark that denotes "front." That notch or mark needs to point to the front of the block. It's important because the rotating assembly is designed to rotate only one way. The rods usually have additional meat on one side to handle the stresses for the rotational direction.

Hopefully you have a shop manual as it will lay most of this out for ya and they have good pics.

We're here if you need us!

Good luck!

Steve

 

[Apogee]

Todd,

I was looking carefully at the pics of the pistons and it looks like I was wrong regarding the pistons being marked. Often they are, but in this case the ones in the pic don't appear to be. Hopefully your new ones are. Per the Intertec manual below is how the assemblies are to be installed. Unfortunately, it doesn't mention orientation of the piston itself on the rod:

"Note that numbers are stamped on the sides of rod and cap and should be on same side when assembled. Install piston and rod units so numbers on rod and cap are toward fuel injection pump side of engine. Tighten rod screws to 26-30 N.m (20-22 ft.-lbs) torque."

Steve

 

[Apogee]

Todd,

A couple of final tidbits then I'll leave you alone:

When reassembling, coat the cylinders with engine oil before installing the piston/rod units if you didn't the first time. It helps with wear on initial start before it has oil pressure.

I'm afraid I might be too late with this but figured I'd mention it anyway. Since you're installing new rings, you need to check the ring gap to make sure they're not too tight. This is important because once they heat up and expand, if they don't have enough clearance, they will either score the cylinder or break. Just because they're new doesn't mean they're correct. If they don't have enough clearance, file the ends until clearances are correct.

Finally, carefully check the rings to make sure you've got them on the pistons with the correct side up. The manual or instructions that should have come with them will show you how they should be installed. Their orientation does matter unless stated otherwise in the instructions.

Hope this helps. Have fun and take your time!

Steve

 

[klipto]

Steve - thanks for the wealth of knowledge.

You had me a bit worried about the pistons; I looked real hard before I installed them to see if the piston went in one way over another and could not discern any markings! So, glad to hear that is not something I have to worry about.

I did (i) oil the sleeve before install and (ii) check the ring gaps, and (iii) I did put the rings in "right-side-up" (I didn't realize the rings had an orientation to them at first so I had to re-install the pistons after I figured this one out).

Thanks for all the advice here. I have spent a lot of time on Youtube, watching people work on (usually car) diesel engines and picked up these tidbits there. Your post, however, should be really useful for someone wanting to do this for the first time. Before I dug in to my engine, I tried to find a single post of someone rebuilding their engine which laid out all these little do's and don'ts for a newbie.

 

[klipto]

Hi OTT,

Quick followup - I got everything buttoned back up and the tractor runs better than new (well, new for me at least given I just bought it!). Everything looks and sounds great.

I had to do an in-frame rebuild---and because I did not prepare (in my defense, I had no idea what I was in for), I did the entire thing with the loader still attached (not recommended!). The front assey pulls off pretty easily by removing the 8 or so bolts which attach the frame to the engine block and then gives you great access to drop the oil pan. After that, it was actually pretty easy if not a bit time-consuming. I suspect I could do the same job in a quarter of the time now that I know what to do.

Thanks for everyone's help - and for anyone reading that is on the fence as to whether they can tackle this kind of job, if I can do it, so can you! (I had literally 0 expertise in this sort of thing before diving in). It took me some time, but slow and steady wins the race...

Can anyone give me a good idea for a break-in, given that I put in new pistons and rings? Anything special I should do here?

Todd.

 

[North Idaho Wolfman]

Can anyone give me a good idea for a break-in, given that I put in new pistons and rings? Anything special I should do here?

Drive it like you stole it... Oh no seriously just work it normally, you should be good to go!
And congrats on the rebuild! I know the feeling, I've had my trans completely out and rebuilt twice... first time I thought I covered all my bases but missed a key part (shouldn't have trusted someone telling me it was a completely new part), had an old and bad seal on the hydraulic clutch.

 

[D2Cat]

Todd, congratulations on your project. When you tackle a job you've never done before, fight through the learning process, discover all the details you never imagined and complete the project in working order you change your self esteem. Your success will lead you to accepting more challenging projects because you know you can overcome!