Oil sump plug wont budge

[Joe Wright]

Hello everyone. I went to change the oil today on the car but cannot move the sump plug at all. It's a bolt I've not seen before its basically got a square head. Is there a special tool I should be using? Spanners, socket set, grips nothing is moving it and I'm worried I'm going to snap it off so I've left it. Has anyone got any ideas?
Thankyou
Joe

[Firewatcher]

There are special sump plug spanners, but if you don't have one you can usually shift it with a good mole grip. Have it as tight as you can, and try to make sure you are twisting square with the axis of the plug, not at an angle. Trouble is that they are a taper thread and often over tightened. The other slight problem is that the squared head is also slightly tapered so even mole grips don't bite fully. The special socket doesn't have that problem, but still needs to be kept square with the axis until the plug has loosened.
Pete

[Joe Wright]

Great stuff.
Thanks Pete. I'll keep trying.

[Alec]

Hello Joe,

I have found the best tool for such a situation is the rather brutal Stillson pipe wrench as that bites into the plug. I have welded a nut onto mine so I use a conventional spanner. You can buy replacement plugs with a hexagon inset so an allen key can be used but you won't find them everywhere, Hydraulic or engineering suppiers should stock them. E.g. :- https://uk.rs-online.com/web/p/pneumati ... s/2181820/
I forget if the sump is 1/4"BSP or 3/8" BSP. If you are unfamiliar with BSP sizes, beat in mind the size refers to the bore of the pipe, so a 1/4'" BSP is about 1/2" od very roughly, i.e. about 1/4" larger in diameter, this 1/4" is fairly consistent as sizes increase.

Alec
PS you often find BSP referred to as R in this case or gas.

[Joe Wright]

Okay. Thankyou for that. I will give it another go today. Worse case scenario I'll have to buy an oil pump.
Whoever tightened it up last time obviously went a bit far

[Charles H]

Reply from Jonnydog

Hi Joe,
You won't snap it off - more likely to round the flats off slightly. The main problem is that the head tapers, as does the thread and and getting an open ended to sit properly if tight is difficult. It is often tightened up more than necessary making subsequent removal difficult.
There is a stainless slim square headed ring spanner available for the job, but they still aren't ideal as the sides aren't tapered to match the head.
When they are so tight, they only way I have removed them is with a small pair of Stilsons and then replaced with new.
You can get a magnetic sump plug with a hex head which collects any miniscule swarf in the oil between changes.
It is a standard thread by the way - 'lefty loosy righty tighty' (as some people quote!)

[Joe Wright]

Thankyou very much. Good to know I wont snap it off. I'm going to use stillson on it and then replace it with the plug you mentioned. Was only supposed to be a five minute job. The joys of classic cars.

[johnnydog]

Cheers for moving my post Charles!

[johnnydog]

Here's a picture of the magnetic type - it is a 3/8 BSP thread according to CW, but he has no stock.

3413-Large.jpg (6.43 KiB) Viewed 12735 times

[Clifford Pope]

Good to know I wont snap it off.

Don't be too sure.
I had the same problem with a Volvo 240 gearbox drain plug. Nothing moved it, and a stillson wrench simply mangled and deformed the stump. I set to with an angle grinder and cut a new hexagonal head on the remains, and then hammered on an old socket. I applied full force with a breaker bar extended with a length of scaffold pipe. Suddenly there was a loud crack and the stump snapped off flush with the gearbox.
I was becoming resigned to having to syphon the oil out from the filler plug, but idly touched the broken off plug, and found it was loose.
The force and the shock of snapping it must have broken whatever was bonding it, and it unscrewed easily with bare fingers. If I hadn't played with it it would have vibrated loose in time.