When a simple engine oil change turns into a disaster

(Nick ) #1

Hi everyone. I was doing a routine oil change on my 1982 xj6. I’ve done about half a dozen of these previously without any problems, however, this time the helicoil came out of the sump when i removed the plug.

I have another xj6 engine and removed the sump plug of that to compare it and noticed it’s much bigger than my original sump plug. I think the spare engine is of a 84 or 85 xj6.

What do you think the best corse of action should be ? Do you know what size the tap thread should be if i use the bigger sump plug or should I replace the sump from the 1984/85 motor ?

Thanks for your time and assistance.


(PeterCrespin) #2

The big boy is a bodge. Which doesn’t mean it didn’t work, but…

On the CoolCat Corp website is a self-threading oversize magnetic plug. They also do an EZ Bleed fitting you can glue in place although it runs slow unless the oil is hot.

(Nick ) #3

Hi Peter, thanks for the input. I thought the other plug was way to big to be original, it looks like its more of a suspension bolt than a sump plug.

Good tips, I’ll check out the oversized magnetic sump plug. I’ve never tapped anything before so I just hope i don’t stuff it up and have to replace the whole sump. Apparently there is a correct way of doing it and that is to use grease whist tapping it.

(Paul Wigton) #4

Grease, yes, and it is critically important to keep the tap going in straight, without ‘wobbling.’

(Robert King) #5

Speaking from experience here; if you have another sump with a good plug/thread, I would install it. It is hard to get a tap to start straight enough in a boogered up hole in aluminum for the seal to compress evenly. Just my 2 cents…

(Rob Reilly) #6

Going to the next larger size thread, it is best to get a taper tap, sometimes called a starter tap.
Drill out the old threads to the specified tap drill size of the new thread.
Put grease on the drill bit to pull out all the chips.
Same with the tap.
A possible complication - if the hole is horizontal and at the bottom of the pan, it may be difficult to drill and tap it to a larger size and still keep the hole at the same axis relative to the sealing face.
Are you going to try it while still in the car?

(Carl Hutchins, Jr. ) #7

Pete, with the benefit of far greater experience on these engines, than I beat me to it.
The long one to the right is a “FIX”. But, if it matches the threads in that sump, it should be effective.

The one to the right sure looks short! Not many threads to engage! But, I’ve sump bolt of unknown specie on my desk here. I think it
was a new one for my B Ford engine project. Same issue, in my view. Few threads !

With a great deal of fortune,. the threads for the Helicoil may be healthy. If so, the installation of a new one might be the short way home.

The good and the bad is that the sump is alloy. Easy to cut, the right way and the wrong way,

Give yourself as comfortable a working position as possible and as Paul says, A good sharp tap., a proper driver and straight in. No wobbling allowed. , ,.

There are some awful fixes out there. Avoid them. One a kind of rubber expanding plug to insert!!!


(Gary Crosby 75 XJ6L, 85 XJ-S, 09 XF Supercharged.) #8


The copper sealing washer is likely your culprit. Many people don’t realize copper washer are a single use seal. They are annealed and soft when first used, but once tightened, they work harden and often do not reseal. So… they often leak and people try to tighten more until they strip the sump pan.

I recommend stopping by your auto parts store and find the next size larger pan bolt and corresponding tap. To help alignment…you can make a simple tap guide with a large flat base and a tight clearance hole for the tap. That will give you the best chance of getting the threads in straight. Obviously skewed threads would cause the sealing faces to not align and offer a poor seal.

Unlike standard taps which push chips forward…there are taps that are designed to eject the chip swarth out of the hole…but for a one time use…maybe cost prohibitive.

You could try reinserting a replacement helicoil and use thread locker on it…but I wonder if the heat in the oil would breakdown the thread locker.

It will take a little time…but this is not a disaster.



(SD Faircloth) #9

Why not just start over. Take off the pan. DIY or have a shop weld over the existing hole. Maybe cut out a round piece of similar metal larger than the hole, weld it on. Then drill and tap a new hole to any size and thread pitch you desire, or match the existing plug.
Long time ago, I mucked up one of the three spark plug holes on an outboard engine. A church buddy of mine, who worked at a Porsche race shop came over. Drilled it out, retapped and put in a helicoil. Did not phase him at all. Took maybe one hour. He even came over with a set of drills, taps and helicoils. SD Faircloth

(Nick Saltarelli) #10

Not seeing this particular, and important, move when cutting new threads with a tap I’ll chime in. You should frequently back cut the swarf as you go along. That is, turn the tap clockwise a quarter turn to cut the thread then turn it back a quarter turn to nip off the swarf, then repeat. You may otherwise spall the new thread.

(Nick ) #12

True, going in dead straight is going to be crucial. It’s also what’s concerning me most as i’ve never tapped anything before.

(Nick ) #13

Hi thanks for the input.

I do have another sump, however, it’s the sump that i took the HUGE bolt out of (shown on the left in the photo). The fact that the plug/bolt is so large must mean it’s been tapped out and made larger previously. They do however appear to have done a good job over sizing it.

What’s involved in replacing the sump ? I take it i have to either drop the front suspension/steering rack or remove the engine ? It would be great if it was just a case of dropping the steering rack but I don’t think it would be that simple.

(Nick ) #14

Thanks Rob, this is exactly the step by step instructions i was looking for.

(Nick ) #15

Hi, thanks for the tips.

Unfortunately, there isn’t much left left of the original helicoil in the sump. I’ll have to remove what’s left of it and like you said use a sharp tap and retapp it. Seams like using grease and being as straight and true as possible when tapping out is the key.

(Paul Breen pay palled it) #16

I think this is good counsel. The removal of an XJ6 sump is not a simple exercise. It has a large and low forward section on the radiator side of the cross member. The engine is mounted on same crossmember. On my XJ6 the clearance between the cross member and the sump is about 1/2”. The engine would have to be lifted well clear and perhaps the cross member (and all attached) lowered? I have recently removed and replaced the sump on my Mk2 - a big enough job - but better as the engine is mounted on the forward chassis rails. Paul

(Nick ) #17

G’day Gary.

Thanks for the good advice about replacing washers every oil change and the tap guide. I’m pretty sure I have a tap guide in the tool box. If not it’s definitely worth getting one. Like I previously stated my main concern is the tap going in straight and true so it’s worth it.

(Nick ) #18

Hi SD, I have the other sump on the spare 4.2 engine which i could use. The large bolt (left in the photo) came out of it. It looks like it’s already been previously tapped and oversized but they did a good job.

My main concern is the time it will take to remove and change the sump. Seems like I might have to drop the front suspension and steering rack to replace the sump. What a headache. At least by changing the sump I’ll know there is no chance that any metal particles from the cutting tap are going circulate through the engine and damage it.

(Nick ) #19

Thanks Nick for the good advice. I have a block of aluminium that i can do a few practice runs on. I think Gary’s suggestion of using a tap guide is a good one so I’ll practice using that as well

(Robin O'Connor) #20

Nick, I would suggest nothing is going to be lost if you first try to tap the sump in-situ. Others have succeeded, join the group and bask in the glory :slight_smile:
If it fails then revert to plan B, and yes thats quite a bit of a job, Subframe dropping is never nice to have to do.

(Nick ) #21

G’day Paul, your right I can envisage having complication after complication replacing the sump.