I need to rebuild the control valve for the rear suspension on my 84 300TDT wagon, and a couple of them appear to be "seized". I sprayed with PB Blaster and tried to loosen after an hour or so. A couple of them came loose, and a couple didnt budge. One of the nuts just started to flatten on the hex sides (I did use the proper flare nut wrench) so I backed off for now.

I sprayed more pb blaster and will continue to do so for the next several days. I will try heating and maybe dry ice, etc. I cant heat too hot because the valve is full of hydraulic fluid.

Any other tips on getting these things loose?



Thanks,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I use a mapp gas torch. with a fire-ex at hand.
dont worry about the hyd. fluid inside, it will get flushed out. wipe off excess fluid befor you use the torch.

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

Blowtorch (on low) on the nut, and compressed air (like for cleaning a keyboard) on the threads. If you hold the air can upside-down the stuff that comes out is quite cold.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

The reason it's cold is that that keyboard cleaner is commonly R 134a (refrigerant). NOT near the torch, please. Some interesting chemistry happens .

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

*cough* mustard gas * *

It's R12 that produces phosgene (mustard gas), I believe . Since R134a lacks the chlorine atom, it produces some interesting flourine compounds, though, because the flourine atom can take the place of hydrogen in organic molecules, leading to many possibilities (few good).

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

I swear that mine was compressed nitrogen.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Get a Vise-Grips Locking Wrench. This is a Vise Grips product that has a v-shaped notch in the fixed jaw, enabling the user to clamp down on three surfaces of a flare fitting without damaging it. The small-sized locking wrench is ideal for 10mm-11mm fluid fittings used with the SLS and brake lines. Beats a flare wrench, and it can save a damaged fitting.

My suggestion is to bang the wrench with your open palm or hit the wrench with a small hammer. Most brake line fittings, fuel line fittings and hydrallic fittings in general bind up. Just simply pushing or pulling on the wrench will round off the connector. When I work on bleeder fittings on brakes, brake hose fittings or fuel line fittings, I hit the wrench with the side of my closed fist! They are not in fact super tight they are bound up. Once cracked loose you can usually hand loosen the connection.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

Sometimes it is propane.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13