Core Plug Blown Out

[BigJimSlade]

Hello there,

I had a peculiar thing happen to my tractor yesterday and I am looking for advice on how best to deal with this problem I have.

I have a Kubota L245DT probably manufactured for the Australian market in the mid 80's. The tractor was working fine the day before last and the next morning I get in it start it up put it into reverse and go to drive out of the shed when suddenly a fountain of oil shot out of the lower right hand side of the block. I switched it off right away and took a look.

I found a small cylinder of metal in the oil on the floor. It is about 5mm long and 5mm wide with a small step on one end of it. This bit of metal had popped out of a hole in the crank case just below the oil filter.

I have looked through the workshop manual and found nothing but in the maintenance manual in the exploded engineering drawings it just says that thi s is a plug but worse than that a plug with a thread and a bolt head. So the manual isn't exactly like my tractor (nothing new there!) so I searched on the net and found references to core plugs.

From what I can gather this bit of metal that popped out is a core plug that has been inserted into the block after the block is cast. The core hole is from the casting process.

Now the funny thing is on ringing around noone has heard of this problem and they all say core plugs shouldn't come out.

So has my core plug just worked its way out over the years or is it a sign of something more serious like too much oil pressure in the crankcase.

Why didn't the oil pressure relief valve handle this? What is this relief valve and where is it. I cant find a reference to it in my manual.

Any suggestions or help will be much appreciated

Cheers

BJS

 

[Ifixcars]

Get hold of a mechanical guage and check the pressure after you replace your core plug. A picture of your core plug would help, but maybe your dealer could sell you the correct replacement. Other options might be measuring your hole and replacing the plug with a drive in replacement of the correct size. Or a threaded type if you can thread the hole if it is small enough.

 

[BigJimSlade]

Hi thanks for the reply.

I have attached a picture of the plug to this message. You can see in the picture a small step in it at the end which is the inner surface facing into the oil gallery. I felt around in the hole in the block and it has also has a step in it on its inner surface. This would indicate that this plug buts up against it and prevent it from falling into the oil gallery when being put in.

So far my plan is to drain all oil. Clean both the plug and its hole and then loctite it into position using a hammer to tap it into place.

Once that has cured I'll test the oil pressure when I have refilled with oil and put a pressure gauge on.

I am still perplexed as to why it happened though. To help me understand I need to know --

Does the Oil Pressure Switch just monitor oil pressure i.e. when no pressure oil light comes on?

Or does the Oil Pressure Switch control flow of oil and monitor i.e. does it divert any oversupply of oil back to the sump? If this is so, if the oil pressure switch fails (loose/broken wire) would there be a build up of oil pressure that would blow the core plug out like it did.

Also is there not a oil pressure relief valve or some safety like it built into the oil pump, if this is the case wouldn't this relief valve work before a plug fires out of the block.

I have also had the 'breather' mentioned to me. I checked it out, I am missing a pipe that connects to the breather but I think this is just an extension so that the breather is extended to the bottom of the engine rather than just poking out of the top.

Could a blocked breather create heaps of pressure? I stuck a wire up the breather pipe and around the corner but didnt run into anything. I was thinking maybe a wasp had built a nest in there. It would be a pain to take of the headcover to fully check the breather so I am leaving that as a later option.

Any advice or comments to help my understanding would be much appreciated.

Cheers

 

[BigJimSlade]

Forgot to mention that the Plug in the attached picture in the previous post is:

11mm diameter and about 10mm long.

Also I figure that the hole the plug fits into leads to the oil gallery because when putting a screw driver into the hole it is able to go in all the way to the handle which would be about 10cm so its a big space back there and I guess it is the oil gallery.

Cheers

 

[Keoke]

Jim, a plugged crankcase vent would cause a build up in crankcase pressure
(blow bye) but not oil pressure.
Core plugs are used to plug internal oil passages that are drilled from outside the block. These holes are then plugged on the outside but left open on the inside.
As to why plug popped, one, oil pump relief valve (usually built into pump) may be stuck closed. A second reason may be a stuck oil filter by-pass valve. This valve only opens up when a full flow oil filter is restricted although this valve will open up when engine oil is cold and it's heavy viscosity makes it difficult for full oil pump capacity to flow through even a clean filter. The valve in this case, will bypass excess oil around the filter. This valve is either part of the filter or built into block. Or three, nothing is hydraulic wrong and the plug may have simply come loose from vibration.
Bottom line, put plug back in with loctite (red or grn) and peen the cast iron a little bit over the plug to add retention value. Check for leak before peening in case you need to remove plug for reseal.
Finally, put oil pressure gauge in sending unit hole and check pressure to see if relief valve is popping off as it should, at spec value.

good luck,

 

[rbargeron]

Couple comments - the pressure in the oil passages is not huge - but it can be 60 or 80 psi if the engine is cold. The normal relief pressure at the oil pump is likely less than that, but when everything is cold, the viscous resistance to flow is high, so local pressure can be high enough to push out the plug. The switch is simply a pressure-activated switch, nothing more. There's no functiokn to divert excess oil (that would be a nice idea).

I think the plug just isn't tight enough. One way to improve the tightness of the plug is to "knurl" it. I've done this with a tubing cutter. Clamp the plug in a vise with a couple spacers small enough so the roller wheels clear them. Use the cutter to make a groove on the plug around the middle. The plug is solid so the tubing cutter will displace material upward on both sides of the sharp-edged wheel, making a couple of bands of slightly increaseed diameter. It will be a slightly tighter fit in the hole. That, and some permanent LockTite ought to do the trick. As always, prompt cheerful refund if advice turns out to be bogus. Take care, Dick B

 

[DieselPower]

You might also try putting some Locktite 518 gasket eliminator on it before you reinstall it. Don't ever plan on removing it again though.

 

[638]

You might be able to tap the hole for a small pipe plug.

ron

 

[hunterridgefarm]

BigJim,

I had the same thing happen to me on my Kubota L185DT. Both time it was cold outside and that plug is made of a soft aluminum. Why its there I don't know but when it came out oil just about all my oil shot out before I noticed.

I found the plug the first time it happend, the second time I could not find it and went to the dealer to get another. He had an exploded view of the block and we were able to find where the plug went and he had one in stock. Same soft aluminum and the dia was a few thousands (.020) larger the the hole. You had to drive it in with a hammer. Well I could see that it was not going to stay so I thought about loctite or threading the hole. Instead I measured the ID of the hole and went searching at Lowes to find something that the OD was slightly larger. I measured everything in the store that was made of metal. I ended up finding a rod that was tapered on one end kind of like a blunt pencil. Bought 2 and still have one just incase I ever need it. It is actually a bolt that after you drill a hole in cement you can insert it and the sides expand. No threads on the end of it.I measured and cut it a little longer than the plug. The tappered end was smalled than the ID of the hole and the other end was larger. I drove it in with a hammer and have about 1/8 of an inch sticking out of the block. I used steel so the cold would not cause it the shrink enough to pop out.

That was six years ago and I have not had a problem since. I do out of habit check it to make sure it is still in.

I have no idea what it is there for. Hope this helps you out. If you can't find any thing PM me and I'll drop the one I have in the mail for you...if I can find it.

David

 

[BigJimSlade]

Thanks all for the brilliant advice. If I can't figure out what to do now then call me a monkey's uncle and I'll go climb some trees and leave the tractor to my pet hamster to deal with This is tops I'm looking forward to the next tractor meltdown so I can post again and be well impressed by the tractor aficiandos community. Cheers again