HST drain plug dripping

[Tractor Gal]

When I got this used tractor, the HST was slowly dripping. I have tried to address the drip to stop it but have only made a little progress. The threads in the transmission case are in bad shape. I've searched
on this forum to read solutions that different people have tried.

I've considered...and am still considering...a helicoil but have concerns. It seems that it would be easy...as well as common...to bungle the job. I got a new bolt and when it threads in, it does begin to grab but then just runs out of thread, it seems.

There are lots of opinions for solutions. I do not want to cause more issues by new tapping, etc. What are some solutions to try that would not entail re-tapping? Would rubber 0-ring be a possibility? I made a leather gasket hoping it would form to the hole and it did help some but there is still dripping. I've asked the Kubota dealer for the specs on this drain plug so that I can get right sizing...nothing was available in the WSM or online that I could find.

Thanks for any help!

Tractor Gal

 

[Captain13]

Napa used to carry repair plugs for this problem For cars and trucks. would probably work for a tractor, too.

 

[hagrid]

Your description of what happens when you apply torque to the plug kinda pigeonholes you into repairing the threads.

 

[Tractor Gal]

Napa used to carry repair plugs for this problem For cars and trucks. would probably work for a tractor, too.

I will have to check to see what NAPA has and how..or if...it will address this particular problem.

 

[Tractor Gal]

Your description of what happens when you apply torque to the plug kinda pigeonholes you into repairing the threads.

That's what I'm afraid of, Hagrid. I can do some things but generally I need to spend time mulling over the problem and then spending time mulling over the solutions!

TG

 

[Jim L.]

I think that anaerobic thread sealant would be a problem as there is too much of a gap to keep out oxygen to allow the sealant to cure.

A regular sealant might stop the drips, but the danger is running over something that knocks the plug out and tears out the remaining threads.

I think that the helicoil is the way to go here. It doesn't require a master mechanic. Careful and slow will do the job. And drilling metal, just run the drill on low speed, with lubrication at the tip of the bit(s).

Chips can be removed with a pipe-cleaner (the fuzzy kind) bent into an L to pull out through the tapped hole before the coil insertion.

 

[Tractor Gal]

I think that anaerobic thread sealant would be a problem as there is too much of a gap to keep out oxygen to allow the sealant to cure.

A regular sealant might stop the drips, but the danger is running over something that knocks the plug out and tears out the remaining threads.

I think that the helicoil is the way to go here. It doesn't require a master mechanic. Careful and slow will do the job. And drilling metal, just run the drill on low speed, with lubrication at the tip of the bit(s).

Chips can be removed with a pipe-cleaner (the fuzzy kind) bent into an L to pull out through the tapped hole before the coil insertion.

Now wouldn't that be awful...get the bolt in and not leaking but impossible to remove!

Wish I could see a cut away view of the HST oil pan. It must be pretty thick based on its location and lack of protection. If the helicoil extends above the bottom level of the pan itself, the HST oil would not drain completely.

Right now I'm waiting to get the specs on that drain bolt. I don't have a micrometer, plus I don't want to remove the bolt until I'm ready to do something since all the HST oil has to be drained. This would be a once and done kind of job, I would hope.

Thanks, Jim L, for your thoughts.

TG

 

[dlsmith]

I can do some things but generally I need to spend time mulling over the problem and then spending time mulling over the solutions!

I'm the same way, sometimes I have to set and look at the problem for a while, and then mull over a way to fix it for a while. My record is 20 years. Just fixed that problem about a year ago. Of course it wasn't something I used frequently.

As a guy with a ~50 year history of fixing things. I leaned that fixing it correctly may be more difficult and seem more expensive at the time, but it won't come back and give you grief later.
I just changed the trans fluid in my BX2230, and with that fresh in my memory, if it were mine, I would drain the fluid, drill the hole out so you're working with all new metal, then tap it for the next size metric bolt thread. The one in my case was probably a 12mm bolt, I believe. Get a new bolt that is as close to the original bolt in length, don't want it to contact anything inside the case, and a sealing washer to fit it, they come in all sizes. Flush the case with some mineral spirits or some new UDT to get rid of any chips, put the new bolt in and be done with it.

Just my $.02.

 

[lmichael]

I know it sounds funny but try regular old teflon tape like for plumbing.

 

[Dave_eng]

A comment on the teflon tape first. Remember the drain plug's seal is to the face of the transmission case. Teflon is used where the sealing parts are the tapered threads as in NPT. Drain plugs' threads are not tapered but straight like a nut and bolt.

I helped a skeptical friend with a 1982 Honda 450 today.

His drain hole was messed up and was re tapped but the new threads were not square with the crankcase so the drain plug did not seat flat on the aluminum. He tried every imaginable drain plug washer and gasket. People who suggest re tapping often fail to consider the difficulty of getting the new threads perfectly square with the crank case.

I gave him Loctite 518. An anerobic material. It only cures when there is no oxygen. He smeared too much on and after a day there was still a lot of goo around the plug. I had him wipe up the mess and fill the crankcase. Hours later not a drop. The 518 between the drain plug flange and the crankcase had cured.

Loctite from amazon

I first used in on a Seadoo jet pump and was impressed.

Do not put a washer or seal on the drain plug. Just clean, apply 518 to one surface and tighten.

Dave

 

[kubotafreak]

I would say if there are more clean threads in the housing a longer plug could be used. The other is instead of a crush washer use one of these. If neither of these work, you need to put a Heli coil in. They are not hard. Don't know what kind of tractor you have, but many have plates that come off so if you were afraid about the metal chips... you could work off tractor.

Just to make sure we are talking about the primary hydraulic/trans drain plug under the rear gearcase. If your talking about the one up closer to the engine, that is a split pin plug to drain fluid from the clutch housing. It can weep udt/trans fluid, or engine oil. This involves a split to repair either engine main, or 4wd propeller shaft seal.

 

[GeoHorn]

Kubotafreak has made an interesting point in distinguishing the HST drain plug from the split-pin plug which is SUPPOSED to weep any fluid which accumulates. HOwever, the split pin plug is also not critical to seal tightly due to the nature of its’ job. So it is unlikely that is the case.

The think I believe important for Tractor Gal to consider is: If indeed it is the HST drain plug which is leaking...then it is IMPERATIVE that it be properly repaired. The last think you want is to be out working your tractor and have it come to a dead stop because that defective/loose drain plug fell out in the field.

I believe the BEST repair will be either a “Heli-Coil” insert and a soft copper or crush washer.... OR.... drilling out the hole and tapping for the next larger plug/bolt. Any machinist or mechanic with only average talent can do this “square” and not end up with the issue mentioned by Dave_eng.

AND DO NOT USE LOKTITE or any other “thread locker” on a drain plug. Those products are not “sealants” they are threaded-fastener-Locks....they do not work well with damaged threads anyway... and you must not find yourself prevented from using the drain-plug in the future. (Been there...done that.... when a service-shop Lok-Tited my drain plug on my truck without my permission. When I found out it was a nightmare getting them to pay for the repair which included complete replacement of the oil sump. On a tractor that may be tantamount to replacing the entire transmission/HST housing/casting and you certainly do not want to create that monster.)

 

[Tractor Gal]

Kubotafreak has made an interesting point in distinguishing the HST drain plug from the split-pin plug which is SUPPOSED to weep any fluid which accumulates. HOwever, the split pin plug is also not critical to seal tightly due to the nature of its’ job. So it is unlikely that is the case.

The think I believe important for Tractor Gal to consider is: If indeed it is the HST drain plug which is leaking...then it is IMPERATIVE that it be properly repaired. The last think you want is to be out working your tractor and have it come to a dead stop because that defective/loose drain plug fell out in the field.

I believe the BEST repair will be either a “Heli-Coil” insert and a soft copper or crush washer.... OR.... drilling out the hole and tapping for the next larger plug/bolt. Any machinist or mechanic with only average talent can do this “square” and not end up with the issue mentioned by Dave_eng.

AND DO NOT USE LOKTITE or any other “thread locker” on a drain plug. Those products are not “sealants” they are threaded-fastener-Locks....they do not work well with damaged threads anyway... and you must not find yourself prevented from using the drain-plug in the future. (Been there...done that.... when a service-shop Lok-Tited my drain plug on my truck without my permission. When I found out it was a nightmare getting them to pay for the repair which included complete replacement of the oil sump. On a tractor that may be tantamount to replacing the entire transmission/HST housing/casting and you certainly do not want to create that monster.)

The leak is definitely the HST plug. I am not blonde but I do know where the HST plug is located.

Teflon tape is not recommended for this application, as I view it. Teflon tape has its place but getting into the HST system would not be good. And, the sealant is also a big question in my mind, mainly because... as GeoHorn mentioned...there is a chance that the drain bolt would not release for future oil changes. That would be a greater mess, just as he experienced.

So, I, too, come back to the Helicoil. I looked at Time-serv (I think that's the name) which is quite similar in application. It is quite a bit more expensive and I'm not certain it's going to offer that much additional help.

It appears that this bolt is 12mm but I am waiting to get the exact dimensions from the Kubota dealer before I proceed further. Meanwhile, I may try a soft copper washer just to see if that would help. The washer that comes with the bolt from Kubota has a very slight ridge of rubber ( or some material) that should do the job to stop the leak but it doesn't. And, of course, that's because the bolt was apparently cross-threaded.

Again, if I could see a cross section of that area, it would become clearer. A longer bolt may work but I would think Kubota would've provided the bolt with the length needed. Going further up into that pan with a longer bolt may cause other problems.

Thanks again for all the thoughts. I still continue to mull. As additional info comes into the picture, perhaps the solution will become more clear.

TG

 

[lmichael]

I used it on my oil pan because the previous owner buggered the threads a little. If you do it right there is no danger of it "getting into" anything

 

[Glowplug]

Bubble Gum

 

[Russell King]

Dave-eng’s post on Loctite reminded me they have a product that repairs threads.
See this link

Loctite 28654 Loctite Form-A-Thread Stripped Thread Repair Kits | Summit Racing

Free Shipping - Loctite Form-A-Thread Stripped Thread Repair Kits with qualifying orders of $109. Shop Thread Repair Kits at Summit Racing.

www.summitracing.com

I have no experience with this so can’t comment on it other than what do you have to lose but money to try.

All loctite products require a really clean surface to work so clean the inside hole and plug very well before any attempt with any of their products.

 

[dlsmith]

Whether you put a Helicoil or Time Sert in, you are still going to have to drill the hole out and tap it, so why not just go the next bolt size larger and skip the cost of an insert and not have to worry about the Helicoil on Time Sert backing out at some time in the future?
Having serviced mine recently, I stuck my pinky in the hole to feel for any chunks, and the casting is about 1/2" to 5/8" thick there.

 

[Tractor Gal]

Bubble Gum

Interesting...plus, I enjoy bubblegum.

 

[Tractor Gal]

Dave-eng’s post on Loctite reminded me they have a product that repairs threads.
See this link

Loctite 28654 Loctite Form-A-Thread Stripped Thread Repair Kits | Summit Racing

Free Shipping - Loctite Form-A-Thread Stripped Thread Repair Kits with qualifying orders of $109. Shop Thread Repair Kits at Summit Racing.

www.summitracing.com

I have no experience with this so can’t comment on it other than what do you have to lose but money to try.

All loctite products require a really clean surface to work so clean the inside hole and plug very well before any attempt with any of their products.

Interesting product, for sure. I'll have to mull on this one. NAPA doesn't have it available online and the local NAPA is already closed for today. Thanks for the info.

TG

 

[NCL4701]

If the plug won’t tighten and hold to the point there’s no chance it’s going to randomly fall out then obviously you have to go with one of the various options for rethreading oversized, heli-coil, etc.

If it WILL pull up tight and is secure but is leaking because the cross threaded state it’s in has it a bit too crooked to seal properly that’s a different issue. I had a Jeep Cherokee with a straight six quite a few years ago that had that problem. My wife drove it and it needed an oil change while I was out of town for work for several weeks. When I got home she told me it had been leaking ever since the oil change. She’d taken it back once and it was better but still leaking whether running or not. Turned out they cross threaded the plug, then put in an oversized “repair” plug but didn’t get it lined up straight so it wasn’t in any danger of falling out, but the copper washer wouldn’t seal correctly. So, for the next 150,000 miles I would drain the oil quite thoroughly, clean the mating surface of the oil pan and plug with whatever grease/oil solvent was handy, put a bit of RTV silicone around the hole in the pan, install the plug, and then wait several hours before refilling with oil. Took pretty much all day to change the oil, of course with many lengthy breaks, but it never leaked and the silicone didn’t create any mechanical resistance to removal at next oil change.

Could be I’m lazy but if the plug was secure and just not sealing, I’d probably do that before I busted out the drill bit and tap, potentially putting drillings in the pan.