Following a series of stupid mistakes, I overheated my 1994 850 2.3L turbo. Soon thereafter. although the car seemed to be running ok, a great deal of pressure built up in the coolant system, and I had leaks in the radiator and (new) expansion tank. The coolant pretty well drained out of its own accord. I tested the compression and I have about 35% lower compression on cylinder 4 than on any of the others, which vary by less than 3%.

I figure I have at best a bad head gasket, or a warped head, or at worst a problem in the block. My first thought is to pull the head and take a look. But, from what I've read in my Chilton's manual and on this site, I may never be able to reinstall the head or reassemble it once I pull it apart. I will get a Haynes manual, which some on this site have implied gives better instructions and a possible work around to various Volvo tools required, but I guess I have my doubts that I'll find anything there that will help all that much.

I figure my options are to get a used or rebuilt engine assembly and replace the entire engine or to tow the car to a mechanic to have the head done.

Does anyone here have any practical solutions to the cylinder head reassembly/reinstallation problem, or practical advice or alternative options to those I've suggested?

The Haynes manual is very good for the head replacement. Like PBH said, using common sense is just as important. And the rings are usually good in these engines.
You probably need a new head gasket and get the head re-machined flat. This is also a good time to replace valve seals. Goodness, 20 valves!! And I thought doing 12 was a lot in my 164.
It is cheaper to buy an entire engine than buying a "reconditioned" head, so if you do it yourself, you will be ahead of the game.
I would just buy the valve cover gasket glue at the dealer, no shipping charge.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

Thanks Klaus. I'll pull it apart as soon as I get that Haynes manual. Cheers, Chris.

I did something even dumber. So dumb I won't say what it was. Suffice to say I was right where you are.

I chose to fix my car myself, and it is a very big job. I got 80% of the way through the removal and asked myself 'why?'. In the end I got the head off (not easy) and looked at the bores. They were like new, even with 120,00 miles, and poor maintenance.

At that point I knew the car was worth fixing. I had my turbo rebuilt, pulled the valves and put in new oil seals, I replaced all the seals in the head, the head gasket, head bolts, and replaced all the vacuum lines. All time consuming jobs, and all necessary to restore the engine.

It took me a few weeks (I was busy at work) but my car fired right up ran like new when I was done, and it is very satisfying to 'bring it back from the dead'. I have gone 30,000 miles since I did it and the car still runs great.

If you are mechanically competent then go for it, if not, pay a mechanic, because it is a difficult job. I doubt many people on this forum have tackled that job. Or could.

Two more things, 1) it is not a cheap repair, so make sure the car is worth it. Maybe just pull the head and see if the engine is still okay. Just to pull ht ehead is several hours labor.

2) I neglected to do it, but you should get the bottom of the head machined if you are going to re-use it. Or look for a used head.

PBH--Thanks for the info and the advice. I am mechanically adept (I have replaced heads on other cars, and also replaced engines on other cars) so I think I can probably manage either job. Also, I have another car to drive in the meantime, so I can take my time and do it right.

However, the part that I am most concerned about is re-installation of the top part of the head (cam cover, valve cover), over the cams. Everything that I have read says that I will need special tools for "cam realignment" and to pull the top half of head down onto the lower half before installing and tightening the bolts. Did you have these tools, or did you come up with a work-around?

Thanks again. Chris.

There are lots of tools required, and some band-aids for your knuckles, but no special tools.

The cams can be re-installed in the lower half and the upper half is just slowly pulled down using some longer bolts. Get the two halves close and swap out the longer bolts for the factory bolts and you are good. I am sure there a people here that will say your engine will never run again if you do this. Just use some common sense and pull the two halves together slowly and evenly. You also need to make sure the oil seals are fully seated when you are done, otherwise they will pop out when you are driving. (Ask me how I know).

You will need a special orange Loctite sealant to seal the heads, it is also used on Porsche engines, so I had some already. Pelicanparts.com has it if you can;t find it locally. I do no remember the part number.

After that you just align the cams as you would for a new timing belt, and you can fire it up.

Last piece of advice: Do not lose any of the 7mm bolts, they are a bastard size and the dealer doesn't likely have any. Again, I know this, trust me.

If you need help email me here: ab7225 'at' gmail 'dot' com

Thanks very much, PBH. I'll pull it apart this weekend and see what I find. Hopefully I'll be able to manage to get it back together without too much hassle. I really do appreciate the advice and help. Cheers.