Volvo MD11C (1977 vintage) Exhaust manifold Expansion Plugs (freeze plugs)

Hello Everyone,
Since my last post about getting the engine bled I have been accumulating some more spare parts including a used exhaust manifold. I got this used manifold it had no expansion plugs in it (I would call them freeze plugs but Volvo seems to call the expansion plugs). I managed to get what I think are the right expansion plugs (35 mm) and advertised as right for MD11C. The expansion plugs are circular and concave or convex (depending on which side you look at them). It looks like you could put them into the manifold either way (so from the outside of the manifold you would be looking at the convex side or the concave side once installed). My questions are:

which side should be facing outward when into the manifold convex or concave?
Does it matter which side is facing out?
How do I install them?
Looks like you just tap them in with a hammer or something
Do I use some kind of sealant on them when I install them to prevent leakage from them?

I have the plugs and have cleaned out the manifold with a mixture of water and muriatic acid (neutralized afterward with baking soda and water) and am ready to install the plugs but not sure how to proceed. Thanks in advace Carole in FL

I didn't hear from anyone (probably my poor description) so I went ahead. Here is picture of the "plug" installed. I figure I had a 50/50 chance of getting it right. Here is a picture of one of the expansion plugs installed in the spare MD11C manifold. Took it to an auto shop and they put them in. They put some kind of goop on them to prevent leaking. As you can see they are installed so from the outside of the manifold you are looking at the concave side of the plug. I want to change this manifold out with the one on the engine so I can clean out and condition the one that is on it now. Does this look ok to anyone? I don't really want to go to the trouble of changing it out if it is going to leak or is wrong side out. Does this look OK to anyone or does it need a redo?

Frost plugs are generally installed from the outside with the concave side facing out. Can't see the photo, but if that is how they are installed, all good.

Thanks Aliboy,
That is exactly how they are installed concave side facing out...Yipee! My 50/50 chance worked out. I do still wonder whether the automotive "goop" they used is sufficient to prevent any leaks. Since I live in FLorida I was thinking I could have them "soldered" around the edge or whatever other sealing technique could better guarantee no leaks. But then I guess I might would have to get the plugs out again (no idea how without ruining them)...any thoughts this?

Also since you might check back, I got and installed an only slightly used exhaust elbow. The one I took off is pretty corroded inside but might be able to be returned to service in a pinch if I could clean out the corrosion inside. I have read the term "boiling out" in some kind of tank that gets rid of the corrosion on these types of items and am wondering where to take it to have that process done if it will work. Can't just get to every part of the inside of the elbow with a wire brush or anything. I could try muriatic acid mixture. Do you know of this "boiling out" process, if it would work for this type of thing and how to locate a shop that has such a tank? I'm guessing some automotive shop?

Oh yes, gotta thank you again for your help on bleeding the engine. I am still having some problems with it starting right up after it sets a few days of sitting but have not tried everything on the list yet. There is a tiny leak at the base of the part that screws down into the injection pump and I am suspecting a bad O'Ring that is listed on the exploded view so I have ordered one of those. I think it is going to be fun to try to take that part out of the injection pump to replace the O'Ring since there are a couple of springs in there...(visions of flying parts...gotta work up my nerve).

Thanks for responding,
Carole

Not sure what eats rust. Muriatic acid will generally clean out 'scale' (calcification type stuff), but not sure about the rust. I would get a flake of rust or a rusty bolt etc and drop it in a small amount of acid to see what it does. I don't know the term 'boil out' so not sure what this means. You could try talking to a local radiator shop or a marine shop that cleans heat exchangers etc to see if they have better ideas.

A quick Google produced these ideas. Bottom one might be the 'boiling out' one?
Soak rusted items in phosphoric acid. It dissolves rust quickly, but the acid attacks iron very slowly. Use the shortest time that removes all of the rust. Naval jelly, which contains phosphoric acid, is often used to remove rust. It can be found at most hardware stores. Oxalic acid and hydrochloric acid can remove rust, but they eat into the iron quickly, so loss of metal is too likely. Follow phosphoric acid rust removal with treatment for rust prevention, such as Boeshield T9.



5Remove rust with a method called electrolytic rust removal. Mix one tablespoon of sodium carbonate, found at pool supply stores where it's sold to raise the ph level, into one gallon of water. Connect the rusty part to the negative terminal of a 12-volt battery or charger. Hook up a scrap of iron or steel to the positive terminal. Soak the rust off the iron with the sodium carbonate solution. This method leaves a black oxide coating and doesn't remove any of the good metal. Use rust prevention such as Boeshield T9.



6Soak several bags of black tea in two cups of boiling water. (Use more for larger rusty iron.) Soak the rusty iron for up to 8 hours.

thanks Aliboy,
Wow those sound like good ideas. I think I might try the electrolytic rust removal method and see what happens. As for the fuel injection pump....I'll just have to take my chances with trying to take it apart in place to replace the bad O'Ring. I thought I bought a used spare a injection pump a long time ago but have not been able to locate it.

Thanks Again!

I cleaned my exhaust elbow with a mallet and wire. I banged on it to loosen the rust and dumped the flake out. I used the wire to break the big chunks. Repeat until you can shake the manifold and not hear loose rust rattling around.

Electrolytic rust removal works great also. It is over kill for a manifold, but if you want to amaze your friends, stick the old cresent wrench that has been in the salt air too long into a bucket as the procedure suggest. Hook the wrench to the neg! It will loosen the little slide and worm gear right up!

The boiling out or "hot tank" is what engine shops use to degrease engine blocks before machining. Beware that some use caustic solutions. They work well on grease, but will eat aluminum.

Thanks Glen for responding. Sounds like the method you describe to bang on it to loosen will be a good 1st procedure.