How To Replace The Head Gasket On A Volvo 850 (page 6)


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Cylinder Head Removal




It is now time to remove the top portion of the head. Before doing this, you want to secure the camshafts so that they stay in their correct positions and come off with the top of the head. I have read where one person said that this was not necessary, that you can just take it apart and pay attention to the camshaft positions when you reassemble. I played it safe and secured them though, as I definitely didn't want to have to buy a new camshaft (or two) if they broke loose, hit the concrete, scraped up a lobe or two, and were ruined. But before we remove them, let's note the position the camshafts should be in:


Note that on the back of the engine (the distributor end), the groove on the intake camshaft is ABOVE the seam of the head, while the groove on the exhaust camshaft is BELOW the seam of the head. This picture was taken before removal with the old sealant showing. If you look closely on the intake camshaft, you can see an "I" as the last letter of the part number stamped there (about 8:30 just below the groove). There is an "E" (at about 2:30 in this picture) in a similar location on the exhaust camshaft too.





Also note that on the front of the engine (the timing belt end), the intake camshaft has two holes on top, while the exhaust camshaft has one hole on top.





To make a tool for securing the grooved ends of the camshafts, I decided to use just a simple piece of wood (1" x 4") as a bracket and two pieces of the steel stock (1/8" x 1.25") to fit into the camshaft grooves. I cut a piece of 1x4 to about as long as the width of the head (red outline). I then put the bolts back in the end of each camshaft (yellow circle) and left them protruding to the edge of the head so they would touch the wooden 1x4 in the next step. I then dabbed just enough engine grime on the heads of each of the bolts so that when I held the 1x4 parellel with the head (red outline) and pressed it against the bolt heads, I was left with an impression of the outline of each bolt head on my piece of wood. The blue circles show where the bolts to secure this will go.






I then took a circular saw and made cuts in the 1x4 that were centered on the bolt head marks and parellel with the long edge of the 1x4; the cut for the intake was made just above the center of the bolt head and the cut for the exhaust was made just below the center of the bolt head. I then saw how far into the cuts a piece of steel stock would fit and added to that the depth it would take to reach from the 1x4 all the way into the grooves of the camshafts. These two pieces of steel were wedged into their cuts on the 1x4, using some folded paper around the end of the steel for added thickness so that they were very snug and tight when I drove them into the cuts on the 1x4. These two pictures were taken when the top of the head was already off so that I could better show what I am talking about.





I then held the 1x4 in place, with the steel stock inserted into the camshaft grooves on either side, and traced onto the 1x4 the outline of the cam position sensor housing and the outline of the distributor housing. Then I made another tracing of both of them on paper, punched the bolt holes into the paper with the tip of the pen, applied it to the tracing on the 1x4, and determined exactly where I needed to drill two holes so that the piece of wood could be secured with a distributor housing bolt and a cam position sensor bolt (T40).






Next, I the inserted the bolts and secured the 1x4 bracket onto the engine with them and with the steel stock firmly inserted into the camshaft grooves. I did have to drill a hole large enough for the head of the T40 bolt to be countersunk, due to the short length of it.






The timing belt ends of the camshafts are much easier to anchor. Reattach (on the timing belt end) two of the T30 bolts that secured the black cover to the top of the engine. Wrap one end of a wire coat hanger around one of the bolts, pull and tightly wrap it around both ends of the camshafts, then pull it tightly around the other bolt and secure it as shown. You are now ready to start removal of the head.

Remove the 40 bolts securing the top cylinder head to the bottom cylinder head (10mm). There are 24 of these along the center of the engine surrounding the cylinders, and 8 along the front and back of the engine. These should be removed starting with the outer edges and working inward in a criss-cross pattern.






There are parting lugs (yellow circle) at every location where there is a dowel (red circle). There are 5 of these, 2 in front and 3 in back. I took two regular screwdrivers, laid the blade of one flat on the bottom lug, placed the other screwdriver blade on top of the first and pryed upward against the bottom one. This touches none of the "sealing surfaces." Once the gap between got bigger, I could fit the male end of a 3/8" extension on top of the screwdriver blade and do the same. Using this method, you can break the top cylinder head free from the bottom one without having to hammer anything or mar any of the "sealing surfaces."






Once the top cylinder head is completely broken free from the bottom one, carefully lift it off (making sure the camshafts stay secured to the top portion) and sit it upside down somewhere so as not to scratch or damage the camshaft lobes. The anchoring tools on each end can now be removed, the camshafts can be removed (keep them from being damaged), the oil seals can be removed (and discarded), and all of these disassembled components can be cleaned. Take care not to scratch the smooth sealing surfaces, keeping in mind that aluminum can be damaged by anything made of a harder metal (such as razor blades, putty knives, scrapers). I used degreaser, gasket remover spray (very strong stuff), and pieces of old credit cards that I cut to fit whatever location I was scraping off. The plastic would abrade and wear down before any damage to the aluminum head could occur, since the aluminum is harder.






Your remaining lower cylinder head should look something like this. I sopped up all of the motor oil I could with the blue paper (shop) towels that I like to use. I did this in order to try and prevent having a big mess when I removed the head bolts and the lower head portion.






This is the sequence that the head bolts are to be removed in, starting with the outer edges and criss-crossing as you work your way inward. Using a 1/2" drive breaker bar, extension, and 6-point 14mm socket, back each bolt out 1/4 turn in the sequence shown and repeat until they are loosened enough to remove by hand. After I had backed each of mine out just 1/2 a turn, they were loose enough that there was no resistance at all on the breaker bar, but keep to that sequence until you're sure they're all loose. Completely remove all of the head bolts. You have to use new head bolts when you install the new head gasket, as these are torque-to-yield bolts (that actually get "stretched" a little), but keep at least one of your best-looking old bolts to chase your threads with later.





Once all of the head bolts are removed, lift the lower portion of the head off of the block. There are no dowels between the lower head and the block like there were between the upper and lower head sections, but there are two of the bolt holes (circled in red) that have short little protrusions for alignment and securing of the head gasket and head. I broke the head loose from the block without any immense effort, gently tugging a little all around, pulling on exhaust side studs and intake port holes all around. The lower head is a little heavy (maybe 50lbs?), so when it does break loose, you may not want to lift it by yourself. Just make sure you don't allow any trauma to occur (drops, etc) that would mar the surface of the block or either surface of the lower head. You should have somewhere padded to place the lower head - or stand it on it's end. After the head is off is the easiest time to remove the lower thermostat housing (T40).





The old head gasket has been removed in this picture. Notice how it is a little clean around the edges of the piston on cylinder 5. This indicates there was definitely a head gasket leak that was allowing coolant into the combustion chamber, which then turned into steam which cleaned some of the carbon off.

You can now take your head to a machine shop and have them check it for warpage, vacuum test the valves to see if you need a valve job (mine did), put new valve stem seals in, and plane it or resurface it if needed. The lower portion of the head is all they should need (or needed of mine). There was a 2 day turnaround at the shop I took mine to, so that gave me some time to do other things like cleaning the upper head portion, the PCV system, the engine block, the intake manifold, the camshafts, the cam pulleys, prepping the intake components with new gaskets, replacing all the O-rings and seats on the fuel injectors, replacing the water pump, and just about anything else I could think of to clean and prepare for reassembly.



1 2 3 4 5 Page 7 - Component Cleaning and Miscellaneous Work Before Reassembly 8 9 10



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(This tutorial is written, sponsored, and hosted by TracysTrueSoaps. I make quality, pure, gentle soaps that are also great at removing grime after working on a vehicle. Please support my site by checking out my soaps. People of all ages LOVE 'em [especially ladies] and they make great gifts for almost any occasion. Thanks so much!)