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Drain Plug

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Clive B 126/07/2018 16:41:10
94 forum posts
50 photos

Hi Guys

I'm having difficulty in finding the correct seals for my car drain plugs.

I assume they should be copper or aluminium, because of the style of plug I've been using rubber O rings with a smear of sealer, which is what I will continue to do if all else fails.

The outside diameter of the threads is 19.8mm but its got a sort of an undercut just below the head which with a thin washer makes for a very sloppy fit.

Does anyone know where I can get suitable seals for it, I've included a photo of the plug so you can see what I mean.

Thanks to anyone who can help


not done it yet26/07/2018 16:49:26
4503 forum posts
16 photos

I expect they are “crushable” washers. Try that in your search engine. Expensive as one-offs.

Brian G26/07/2018 16:57:28
672 forum posts
26 photos

Ebay? M20 x 26 x 1.3mm Aluminiu, 10 for £5.20 **LINK**

Part of me would be tempted to use the M18 x 26 and thread them


Speedy Builder526/07/2018 17:03:06
1985 forum posts
139 photos

If you want a softer seal, look up DOWTY WASHERS. An 'O' ring on its own is not a good idea as it can be squashed outwards.


duncan webster26/07/2018 17:06:13
2543 forum posts
49 photos

could it be a Dowty washer


failing that try the dealer!


Edit: Speedy Builder types faster than me!

Edited By duncan webster on 26/07/2018 17:06:49

HOWARDT26/07/2018 17:49:48
536 forum posts
15 photos

Copper washer would be the norm, appears to be 3/8BSP. Washer face on plug is bigger than bonded seal requirement. I think copper washers are folded to give a crushable seal. Halfords or any other motor factor stock them, Halfords and probably Amazon et al sell them in assortment packs.

Chris Evans 626/07/2018 18:41:22
1627 forum posts

After years of servicing my own vehicles and coming across many damaged drain plugs I always fit a new plug and washer. It is part of the spec for some Ford and Land Rover.

Try Beal Automotive web site for all workshop consumables.

JasonB26/07/2018 18:45:28
17850 forum posts
1954 photos
1 articles

Can you not get the correct OEM item from a parts supplier for your make of car or is it that old they are no longer available?

Too big for 3/8" BSP and too small for 1/2", Probably M20 fine.

Mike Poole26/07/2018 20:13:46
2544 forum posts
60 photos

There is plenty of choice on eBay and I would think most motor factors will sell a packet of them for not too much money. A sump plug failure is good bye engine and the cost a lot more than a washer. The warning light is usually of the "it's too late" variety unless you have an oil level warning. This is one place a bodge could be too risky. The plug will not be tight with just an o ring and you will be relying on the sealer to stop it unscrewing. This would be strictly a get you home bodge and no further.


Edited By Mike Poole on 26/07/2018 20:17:02

Mike Poole26/07/2018 20:23:09
2544 forum posts
60 photos


These are on eBay, just choose the size and quantity you want.


Jeff Dayman26/07/2018 20:26:54
1792 forum posts
45 photos

Have a look online for a parts manual for your vehicle. Unless it's extremely exotic there should be multiple listings, or maybe a link to a marque-specific club for your make. One way or the other I expect you will find lots of info. When you find a parts list / manual It should list the correct type and part number of the washer for your car. As Mike Poole said, if the washer seal fails or the plug is lost, causing major oil loss, serious engine damage may occur, so I'd get the right washer and torque the plug to spec.

There are also lots of youtube videos of common repairs to many makes. Do keep in mind that there are some folks in these videos who have no clue what they're doing, but if you watch a few videos of the same procedure and they do them the same way (and it makes sense how they're doing them) you can get the gist and figure your own game plan. As I said these videos are great for common procedures- one that may not be obvious or may not be frequently done, but that you haven't done yet. I would NOT trust a youtube video necessarily for internal engine repairs, suspension adjustments, tire advice, or anything control or air bag related.

Just my $0.02 worth, your mileage may vary.

Emgee26/07/2018 22:38:07
1448 forum posts
212 photos

On my Peugeot 2.8 HDI the sump plug sealing washer is flat 1mm thick copper, not a perfect fit because of the undercut but I've had no problems and change oil annually.


Clive B 127/07/2018 14:44:31
94 forum posts
50 photos

Hi Guys

Thank you all for taking the time to reply;

Speedy Builder 5: Yes that’s what I was worried about the O ring squashing outwards as it’s not really contained in that application.

I’ve been having a look at some of the sites you guys have suggested and from what some of you have said a crushable copper washer may be the direction to go.

I’ve included a bit of a sketch to illustrate what I’m trying to get right, you will see the undercut is 3mm wide so obviously any washer thinner is going to drop down into the well creating a gap as shown in view Section A – A.

There must be some way around this, another thing I often find when looking for copper washers is the land always seems to be very narrow, I always have a job finding something the size of the washer I‘ve included a photo of.

I agree with all of you the last thing I want is an oil trail and as already pointed out a very expensive learning curve.


Jeff Dayman: I fully understand what you are saying about videos one does have to be careful.

A parts manual would be very useful, heaven knows where I would find one for an Isuzu Trooper 3.0TD because that’s the car we are talking about.


Emgee: That’s what I’ve been doing until now, putting a bit of sealer over the whole sealing washer but I thought it worth coming on the forum just to find out what others do in the same situation.


JasonB: New plugs, they are on a back order though the main agent and on these Troopers there are 2 plugs on the gearbox fill and drain obviously, 2 on the transfer case, 1 of that size on the front diff, 2 on the rear diff and 1 on the shift on the fly.

So, I’m looking at 8 plugs, the price from the main agent when they have them in stock is £5.31 + vat each plus postage.

I'm not sure of the price for the sump plug and it's a different size anyway.

The service on these Troopers pops up every 6000 miles, so yes if I can find an alternative to the main agent I will.

No topping up of oils on these cars it’s drain and throw away and fill with new every time.


Thanks again fellas for taking the time to reply it’s much appreciated






Edited By Clive B 1 on 27/07/2018 15:00:40

Mike Poole27/07/2018 20:51:44
2544 forum posts
60 photos

I think the undercut is to make the manufacture of the thread easier and provide a space for the washer to squeeze into. If you use solid copper washers you can usually soften them by heating to red heat and quenching in cold water, I am not sure the quench is essential but it does help to clean the scale off the copper. The rolled crush type washers are really single use and should be used new each time. I would have no hesitation in using pattern parts as the dealers must be relations of Dick Turpin. Solid copper is quite ductile and it is surprising how much it spreads. My experience of solid copper gaskets it that they do tighten up on the studs holes after a few uses so they need the holes easing or start again with a new gasket.


Jeff Dayman27/07/2018 22:30:05
1792 forum posts
45 photos

What year is the Trooper 3.0 TD? There are plenty of Troopers left in North America and they have quite a cult following with the off road fans. With the year info I can probably find some references.

I just checked a prominent US based mail order auto parts house's listings and they have Trooper copper drain plug gaskets but only size M14 (14 ID 20 OD) intended for the gasoline / petrol 3.2 and 3.5 L V6's 1998-2003 model years. These smaller copper gaskets list for $2.61 USD on that site. 

The 3.0 TD may be a little harder to find stuff for but again let me have the year and I'll look a bit. 

Edited By Jeff Dayman on 27/07/2018 22:39:25

Clive B 128/07/2018 12:18:27
94 forum posts
50 photos

Hello Jeff

The year of the Trooper is 2000, engine type is 4JX1 so if you know where I can get a parts listing that will be great.

Indecently I don't use it for off roading, well not unless you count towing a caravan off grassy fields as being off roading smiley

Clive B 128/07/2018 12:27:32
94 forum posts
50 photos

Hi Mike

I must admit I haven’t bothered to try annealing the washers, I suppose I thought it a lot of trouble if I can get hold of the correct ones for the job.

If the crushable ones are suitable that’s fine they aren’t exactly a kings ransom to buy, just a bit of a fiddle getting the used ones off when its replacement time.

Howard Lewis28/07/2018 12:28:39
3148 forum posts
2 photos

Both Ford and Perkins use, (or certainly used to) a sump plug like yours, but with a groove under the head to retain an O ring. This cured the seepage that was seen with copper, or aluminium washers, and even taper thread plugs.

The depth of groove controlled the compression of the O ring.

Would it be possible to modify your plug to use this method of sealing?


Edited By Howard Lewis on 28/07/2018 12:29:25

Hopper28/07/2018 13:55:41
4405 forum posts
93 photos

You may be overthinking it a bit. The groove at the end of the thread is only 1.5mm deep. The washer is 5mm wide. That leaves 3.5mm to seal. Plenty. The flat surface on the plug and the sump boss will be big enough to seal all the way around.

Ten million sump plugs a day are used like this. A wide-series flat aluminium washer will do the job fine. Copper went out with carburettors and points.

If you are a belt and braces type like me, put a bit of hard-setting gasket goo on the thread, to both seal and lock it in position as a mild thread locker.

But whatever you do, don't use a rubber o-ring. It will squeeze out of the gap all-together under tension, heat and vibration. Then the sump plug, devoid of retaining tension, will vibrate out. After all the oil has drained out on to the road, the red light on your dashboard will come on to tell you its time to replace your engine.

Around here it's called "The $5,000 O-Ring".

SillyOldDuffer28/07/2018 14:19:12
5631 forum posts
1157 photos

Posted by Hopper on 28/07/2018 13:55:41:

... After all the oil has drained out on to the road, the red light on your dashboard will come on to tell you its time to replace your engine.


Friend of mine has a non-mechanical wife. Driving home one day the red light came on and illuminated the word "STOP". She carried on.

Questioned as to why she hadn't pulled over she replied, 'if the light was important it would have been flashing'.

She's not alone. Most of the world are taught engineering by Captain James T Kirk. He never wrecked the engines on the Enterprise despite Scotty warning him in every episode, 'she canna take it Captain'. The show confirmed popular opinion that engineers are just a bunch of cowardly fusspots...



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