I'm trying to loosen either of the drain or fill plugs on a 1988 Volvo 240 M47 manual transmission.
I relize that the aluminum housing and steel plugs are not too friendy togeher but this is ridicolous!
I'm afraid that I'll crack the aluminum housing or round off the 13mm heads.

Any tips to frre this up?

Other advice is excellent -- never try ANYTHING but a six point, high quality socket on it. Never anything 12-pointed. Some PB Blaster helps loosen it up (soak for a day or two). Smack the plug with a light hammer a few times to jar it a little.

I have used an impact wrench out of frustration which worked perfectly, but DON'T do that unless you are sure. But it sure worked. Again, good, six point socket... The quick motion is really what freed it up.

Also, do the fill plug BEFORE you do the drain plug. Just in case it breaks or something. Obviously this is common sense that one would want the trans full of fluid if the head tore off the fill plug or something.

Never used sunshine on an M47 that I can remember. The fill plugs did always come out.

Also apply anti-sieze liberally to the threads on reassembly. It makes this a discussion of the past.

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Chris Herbst
VA/DC Metro

I had the same problem on my 90 when I got it. First I got 2 new plugs, then tried to get the fill plug out. It had been overtightened since a PO neglected to put the copper gasket on. I got a grinder up there and made the flats broader so I could get a wrench on it -- no go. Eventually ground so much away there wasn't enough to get a wrench on. Let it go a couple weeks and noticed it was a little wet with oil. Was then able to turn it out using a cold chisel. My guess is the heat from grinding (actually an air cut-off tool) heated things up to allow the ATF to work through.

I always use a 13mm 6-point socket on these plugs. Using an adjustable wrench would be asking for a repreat to this whole ordeal.

I am not familiiar with the M47. My experience is with M46od units. However if the plugs on the M47 are hex head I would suggest using either a six point box end wrench or a six point socket. Do not use a 12point. The six point will fit better and have less chance of rounding off the head.

You also might try holding the box end onto the plug with one hand and striking the wrench on the other end with a sharp hammer blow. This will give more of an impact to break the plug loose.

I would also give them a good long soak with PB Blaster or Kroil. Using anything else in an effort to penetrate is (IMO) a waste of time.

Randy

Randy,
I only used a good quality S-K 6 point socket 3/8" drive with breaker bar but did not use my Kroil or PB-Blaster penetrant but I will now.
I was surprised with a short pipe attached for leverage on my breaker bar that how tight these are. I thought the al. case would crack!
My thoughts was heating the aluminum housing around those drain plugs to expand the aluminum. Whadda ya think?

Duck

I would only be guessing and I don't like to do that when the stakes are high.

Randy

Well, I just put Mixture #79 on the drain plugs. PB-blaster with one minute intervals then waited 10 min. and put Kroil on. Maybe more Kroil in a hour or so. I'll try it in the morning with hopefully better results.

I would expect better results with Randy's "hammer a box end" tip, than with your "pipe on a breaker bar", believing that impact vs brute torque is more apt to be effective.

I have little belief or faith in any of the snake oils du jure, after repeatedly soaking a rusted on muffler clamp nut over a period of months—with both P'Blaster and Kroil.

This nut had been run on a used u-clamp by hand, then tossed in a box of parts under the bench. Now it refuses to budge (in either direction) with the 1/2" torque wrench set at 50 ft lbs.

I know I can get this nut off with impact or more force. But the point is that these so-called "penetrants", applied on both sides of this nut, have had no observable effect on what must be simple thread rust and time.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Yep, and in this case penetrant won't make it to the threads. Like you all said, hold the wrench tightly on the bolt and strike it with a hammer. Forget heat and spray ons.

I got 'er done.
Thanks for 'yer help.
Duck