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Technical How to replace crankshaft oil plug at flywheel end

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Technical How to replace crankshaft oil plug at flywheel end

jjacob

jjacob

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Thought I would write up the procedure I used to replace the oil plug located at the end of the crankshaft. This plug is located under the pilot bearing pressed into the end of the crankshaft. I damaged the plug slightly while taking the pilot bearing out causing it to be loose which of course would have allowed oil to get by the plug, dropping oil pressure and making a mess in the bell housing. So I removed the plug and replaced with a new one. When you buy the plug, buy 2 or 3 just in case you damage the new plug while trying to install it. They are VERY cheap.

Make sure to lube the bore and plug with oil. There is a beveled lead in on the crankshaft that you must press the plug past before driving it in. This requires just some patience. It will most likely not go in straight at the start. Work slowly. I drove it in initially with a socket. One side went in about 2mm past the bevel. The other side did not. So I took a smaller drift and struck only the high side until the plug was past the bevel and was level in the bore. Make sure you do not get the plug unlevel in the bore by too much, otherwise you will have to start over.
Once the plug is past the bevel and level in the bore, then take a socket that matches the bore and continue to drive the plug in, checking every few blows to make sure the plug is going in straight. You will know when you are all the way to the bottom as the sound will be very metallic. The depth is around 19mm.
See pictures.
John
 

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Last edited:
Brilliant write-up John, on this and the pilot bush removal. From experience, I think the hydraulic extraction method is more suited to wider, shallower roller bearings. I wouldn't want to risk dislodging the plug.
That disc looks like what we call a core (Welch) plug. Conventionally, those are driven in with the dome uppermost. It is then flattened slightly to provide an expansion seal at the edge. But I vaguely remember that mine was the opposite way like yours.
 
Hi Peter,

Same term (welch plug) is used in the USA. I try to use generic terms that everyone can understand!
The disc was definitely installed originally with the dome facing down. Also, when the pilot bearing is driven in so it seats against the plug, it becomes impossible for the plug to come out.

I want to add that once the plug is past the bevel and level, that you must use a large socket close to the bore diameter. If you use a small drift and hit only in the middle of the plug you risk changing the shape so it is not tight in the bore, and it will be difficult to keep it level in the bore.

John
 
Last edited:
:) I was thinking that "welch" plug was the Americanism......apparently that is the proper name and it is an American invention.
I wonder if the action of hammering in the pilot is meant to push in the edges of the plug and secure it by the reverse of the conventional method?
As you say, it won't actually come out once the bush is rammed home, but I'm thinking of the edge sealing.
You're a very thorough and precise technician John.(y)(y)
 
Peter,

If you look at picture 3 you will see that the plug is much wider than the bore. If you inverted the plug with the dome up, you would end up making the part "dome down" by the time the plug conformed to the bore size. I think that the plug at the side of the crankshaft should be installed as you suggested as you are seating the plug in a shallow depression.
There is nothing in any of the manuals or online showing the orientation of the plug before it is pressed in.
John
 
jjacob said:
Peter,

If you look at picture 3 you will see that the plug is much wider than the bore. If you inverted the plug with the dome up, you would end up making the part "dome down" by the time the plug conformed to the bore size. I think that the plug at the side of the crankshaft should be installed as you suggested as you are seating the plug in a shallow depression.
There is nothing in any of the manuals or online showing the orientation of the plug before it is pressed in.
John
Click to expand...

I wasn't aware that the disc was so much wider in diameter than the bore in the shaft so I can see that you have fitted it in the correct orientation.
I haven't seen this matter discussed anywhere else so it's good that you have covered it so thoroughly. You've certainly made me wonder what's going on under the newly replaced spigot bush in my engine.:eek:
It is a design that people should be aware of when extracting and replacing a spigot bush. I am even more convinced now that by using the hydraulic extraction method you are likely to create this additional job, because effectively, the bore does not have the "blind" end that the method relies on.:bang:
 
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