|
| Search | Car Forums | Gallery | Articles | Helper | Air Dried Fresh Beef Dog Food | IgorSushko.com | Corporate |
|
#1
02-19-2007, 08:25 PM
|
|||
|
|||
|
ENGINE KNOCK 1990 525i m20
cylinder 5 has a knock when revved up past 1500rpms swapped injectors with new injectors. vent tube from valve cover to throttle body filled with mayonaise looking gunk. changed oil cleaned everything out but no white gunk came out when oil change was done. i dont have a check engine or any oil lights coming on on the dash so i really have no clue what could be wrong. sparkplug on cylinder 5 is clean while all other plugs are dirty. With sparkplug for cylinder 5 disconnected there is no knock. Wireset is brand new along with all the plugs.
any help would be greatly appriciated. 
|
|
#3
02-22-2007, 11:27 PM
|
||||
|
||||
|
Re: ENGINE KNOCK 1990 525i m20
Hey Jason:
Please read through all of this a couple of times.... lots of details that may give you a headache! Just got back in town and saw your post. Boy that is strange, my M20 engine did the same thing a few months ago. Just one day out of the blue, it starting running really rough, like it was missing a cylinder. Pulled the VC and sure enough, both rocker arms on Cyl#5 were broken.... I did manage to replace them without pulling the head, or losing the timing adjustment.... I will say its not really easy, but it's cheaper than pulling head, cause you have to buy a new gasket set etc. I also managed to do it without opening the cooling system... Because it is cylinder 5 near the back of the engine, you can do it. What has to happen is that you have to slide the rocker arm journals (shafts) out the front side of the cylinder head far enough to get the old broken rockers off, and get the new ones on.... Sounds simple, it ain't. I will try to recount the steps from memory, please understand the old gray matter isn't what it used to be, so I may forget something... I took the fan shroud off to make some room on the front of the engine. My plan was to take the cam shaft pulley off so I could slide the journals out the front of the head. DON'T do that.... It won't work. No Need to loosen tension on the timing belt at all.... What you do have to do is get the distributor off, and I took the timing belt cover off. There is a cover on the front of the cam shaft pulley that has to come off, remove the bolt in the middle of the pulley, take the cover off, and put the bolt back in. That reveals the "holes" or openings in the cam shaft pulley, the journals will have to pass through these openings as you slide them out the front of the head.... look this over carefully, and now look over that valve train and think about what has to happen.... I kept thinking to myself... this will never work! Remove the rubber plugs at each end of the journals. Loosen all of the valve adjust nuts to remove as much tension as possible from the good rockers. Remove the metal key at the front side of the cylinder head that pins the shafts in place. They won't move if you don't take that out! Rotate the Crankshaft with a wrench (go ahead and take out all the spark plugs!) to position the camshaft pulley opening so that one of the two journals will pass through the opening in the pulley.... Now we get creattive: At least two rocker arms will remain under tension. Make sure that it is not either Cyl 5 or Cyl 6 since you need to remove and re-install those. You have to do one journal at a time, choose intake or exhaust side to start. Now How in the world to get that journal to move, since it is still under tension from at least one rocker arm... it won' t just slide out... Go to Home Depot. Buy a piece of hardwood dowel rod just a little smaller than the journal diameter, about 5/8"? I don't remember.... you want it as close as possible to the journal size but just a bit smaller. Now cut several very short lengths of dowel rod (the reason will become apparent) one about 1 inch long, another 1.5 inches, another about 2.0 inches long.... Get a big crowbar... (3 feet long) yep, thats right, a big crow bar, you will need a lot of leverage. Get a scrap or two of wood that will fit against the firewall between the firewall and the back of the cylinder head... Place the wood scarp against the firewall. It should be long enough to distribute the force of the leveraging crowbar over a fairly large area of the firewall. Position the shortest piece of dowel rod against the end of the journal shaft, and with you third hand lever between the wood block and the piece of dowel rod with the crowbar to apply force the end of the journal shaft to push it forward out the front of the head.... sounds impossible... well it almost is.... Initially it will take a lot of force to start the rod moving. And because you have so little room to work in, you first move it about an inch with the short dowel, then replace it with the medium dowel to push it a little more, then use two dowel pieces to get a little more, and so on.... Not a difficult concept, but really tedious to pull off.... Of course you will have to remove the rocker from #6 first, and continue to push the journal shaft forward until you can get it far enough to remove the rocker for #5. There is enough room to do this without taking out the radiator. (no bleeding of the cooling system right!) To get it back in, I used a hard rubber mallet to tap tap tap tap it back into place, about a millimeter at time, more tedious going back in than coming out... remember to put the rocker back on for #6 before you go to far.... Once you have done the exhaust side, then you rotate the pully again to position it so the intake side can pass through the repeat the process. When I did this, I bought new rocker arms, new valve adj eccentrics, and new valve adj bolts and nuts. But I bought them only for the new rockers.... After I put mine all back together I had a rather loud tapping from under the valve cover, investigation revealed that my valve adjustments did not hold for a couple of "other" rockers and it turned out that I had a couple of nearly stripped valve adj nuts. I bought more nuts and bolts (but not eccentrics), only to find out that the new bolts would not pass through the old valve adj eccentrics. I ended up using the old bolts I had, only the nuts were stripped. But I did have to "clean" the metal "thread" from the bolts...left there by the stripped nuts... My advice: If you can afford it, go ahead and replace all the nuts, bolts, and eccentrics... if you buy new eccentrics the new bolts pass through just fine.... AND, remember to not over torque the valve adjust nuts when adjusting the valves.... I think that may be what leads to stripped nuts, and possibly the broken rockers too.... Good Luck... Post here if you get stuck... I'll be out of pocket til sunday but will check back then....
__________________
ShadeTreeBill 1989 525i Cirrus Blue Automatic 2002 White Malibu (wife's car!) shade tree mechanic - an amateur or otherwise marginally competent mechanic who primarily works on cars out back under a "shade tree" which serves both to provide a cool place to work, and a handy tree limb to attach the block and tackle to remove the engine.
|
|
 |
POST REPLY TO THIS THREAD |
 |
|
|
