83 300dt. small crack in bottom of tank. can i bondo? epoxy? then there is the question of the schmengie fix working under pressure. any ideas? thank you.

I used Permatex gray RTV and it's holding. I didn't prep the surface beyond a spritz of brake parts cleaner and a quick wipe. This was on the SD.

I think thermal expansion is a bigger issue than pressure. I'd want the reservoir to break if the cap ever stuck closed.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

My expansion tank was cracked as well. I tried a number of repairs and none of them seemed to work very long. The tank gets brittle after time and after repairing one crack you usually get another one somewhere else. Buy a new tank, they're not that expensive, about $30.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

This was the first repair on my 190 D back in March of 1989. The old tank was cracked (thermal/brittle issue). It was replaced at that time, and I have not had to replace a second one for over 300,000 mi. Not a bad $30-50 spent.

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Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi

genthemen, thankyou.

When you go to buy a new tank, keep this in mind. MB has since replaced the original part number for your expansion tank with one that was shared with the 126 chassis. The new tank will have an additional hole in the side. This is for a coolant level sensor that the W126 cars had, but not your 123. There is a plug that you will have to buy. Call Phil and he can get you the info. It's only a couple of bucks, but otherwise your new tank will be useless.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member