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Northstar Engines and System Technical Discussion Discussion, Post Head gasket job (need Veteran rebuilders advise) in Cadillac Engine Technical Discussion; I got everything back together but need some advise from the Veteran rebuilders. My car has a very rough idle ...
  1. #1
    JaxxMan's Avatar
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    Post Head gasket job (need Veteran rebuilders advise)

    I got everything back together but need some advise from the Veteran rebuilders. My car has a very rough idle even more pronounced when in gear. (shakes the whole car and has stalled a few times)

    I think my issue stemmed from a small broken head bolt http://www.cadillacforums.com/forums...mall-type.html if you interested in the history here is the thread.
    Because I had to re-install the timing sprockets when I removed the head.

    My question is it possible to be out by 1 chain link (front bank) in the timing chain and still have the engine run ?
    As I drive the car it is slow to take off until I hit about 30 mph, then all hell breaks loose for lack off a better term. It throws me back in the seat until is shifts gears around 55 mph hesitates a bit then off we go again until I'm up to about 90 and then I back off the gas.

    My reason for thinking this is I did a (follow up) compression test and my numbers were very low compared to pre head gasket job. 1-3-5-7 bank all tested OK at 180 PSI and cylinder 1 is where the leak was. The 2-4-6-8 bank all tested at 90 PSI. Could the valves still be partially open before it's completeing the compression stroke?

    Some engine work history:
    Had the heads machined (to clean up the HG leak area) I lapped all the valves installed new stem seals and all other gaskets & seals in the Kit.

    Please advise I would like this sick to my stomach feeling to go away.

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  3. #2
    sts96 is offline Cadillac Owners Fanatic
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    could very well be cam timing check that the cam sprokets are in the correct pin holes for that head (can be installed wrong) then check link postion.
    sts96

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    Yea, if you are seeing a difference in cranking compression between banks then likely the cam timing is off.

    Given what you have done it is pretty easy to to a quick check. Remove the cam covers or at least loosen them and lift them up enough to see the sprockets. Take out the spark plugs so you can turn it over easily. Turn the engine to TDC number one using a wrench on one of the pulleys of the serpentine belt drive. Stick a piece of wooden dowel down the spark plug hole of number 1 and watch is rise and stop to find TDC quickly. If you put your finger over the spark plug port you can feel compression as the piston comes up to know it is TDC firing.

    Once you have found TDC firing, look at the cam sprockets. The timing marks on each of the sprockets should be at 12:00 relative to the cam cover sealing surface. Use a small pocket square to check that the mark is at 12:00 exactly. If all the marks are at 6:00 then the engine is at TDC but TDC intake/exhaust not TDC firing. In either case, all the marks should be in the same spot. If one (or more) of the sprockets is not in the same spot as the rest and/or not at 12:00 then that cam is out of time.

    The other thing to check is that you have the timing dowels in the cams in the correct slots. The sprockets are common and can be installed on the intake or exhaust cams....but you have to put the timing dowels of the cams into the I or E slot depending on which cam it is for that sprocket. Possibly the timing mark on the sprocket will be correct but the cam dowel pin is in the wrong slot. When the timing marks on the sprockets at at 12:00 relative to the cam cover sealing surface all four cam dowels should also be at 12:00.

    Once you have determined that a cam is out of time you do NOT want to unbolt it and try to move it or the cam chain tensioner will rachet out and stop and you will HAVE to remove the front cover, etc. to reset the tensioner. It is possible to retime the sprockets if you use the correct tools, though, without tearing into the engine again. There is a dealer specific tool that looks like a funny pair of vise grip pliers that is designed to reach down into the chain case at the front of the engine and hold the chain tensioner in place while the sprockets are removed. Since the sprocket has to be removed from contact with the chain and moved a tooth to get it into correct time that is about the only way to do it unless you pull the damper, front cover, etc....and reset the tensioner for that bank.

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    Re: Post Head gasket job (need Veteran rebuilders advise)

    chevelle I just spent the last 2 days trying to location the Cam chain tension tool you mentioned. Yesterday at lunch I went down to the Stealership pleaded to borrow/buy it with no luck yet. The service Forman was impressed with how much I did so far and what I knew about this repair. I told him I learned it all hear and this is my first northstar rebuild. (several 4 cyl DOHC motors) He also mention something I don't remember reading, "after the timing is set you should crank the engine over 26 times" not sure where that number came from.

    He also told me "the engine has to dropped and front cover removed to set the timing" after I explained what I read here about using that tool (I don't remember who's post before yours) he said to me "I guess you could use that tool for that, we only used it once for changing a bad head"

    What bothers me the most is I had it setup properly and had to remove the sprockets to put the put the small head bolts in. (Then one broke) Teaching me a lesson for trying rush, I guess.

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    Re: Post Head gasket job (need Veteran rebuilders advise)

    Found the Tool I need.
    The Kent Moore part Number was invalid in my service manual has been updated to J-38822. I called Kent Moore and they wanted $268.?? for the dam thing.
    I did some more searching and found this tool inside Kent-Moore kit # J-41619 It's labeled "4.0L Engine Overhaul kit" and includes a bunch of other tools I didn't have:
    J-38824-1 Valve Spring Compressor
    J-38824-2 See Above
    J-38820 Seal Remover/Installer
    J-39946 Crankshaft Socket
    J-38822 Timing Chain Holder
    J-39313 Spark Plug Port Adapter
    J-38821 Valve Spring Compressor Adapter
    J-38819 Retainer Remover/Installer

    Found it on e-bay for $125.00 WHAT A Deal !!!!
    At this rate I will have my car fixed before I get 50 posts here.

    Thx for your input earlier chevelle & sts96

  7. #6
    WOTMODE is offline Cadillac Owners Fanatic
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    In the future, line up all timing marks before removing the chain, and use zip ties to secure the cam gears to the chain. Also use a marker on the center sprocket and one link from each chain. This way you wont question if you had too much slack on one side of the chain. The reason you have to turn the motor over so many times,(I think eight, not twenty-six) is because the idler sprocket is not exactly twice the size of the crank sprocket. Therefore the timing marks between the idler and crank only synchronize once every eight revolutions. I didn't use any special tools when I did mine, but I've heard a carpenters square works well.

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    Re: Post Head gasket job (need Veteran rebuilders advise)

    well before you pull it all apart and find out that you still didnt install the cams correct listen. i have done this in the car recently and its very easy, you DO NOT need any " special tool " i understand that there is a tool made for it but its just as easier and cheaper to just do it the old fashoned way.

    now assuming that since you just did a headgasket im sure your aware that the northstar motor timing marks ONLY line up every 7 revolutions!

    you WILL have to remove the side cover to be able to see all the timing marks anyways. its very easy to do and i have posted tons of pics here on the forum do a search.

    after you remove the cover rotate the engine until the crank sprocket and the intermediate sprocket line up and check the cams, you need to keep doing this until the cams are the closest to being on time, if you only have 1 cam thats off than the other 3 cams will be lined up and you will be able to see what 1 cam is off.

    then since the n-star has 3 timing chains you will be able to install a wrench on the cams near the pulleys to hold them in place, next have a friend help you hold the wrenches, then you need to remove the hydraullic tensioner for that chain and compress it and install a small nail or pin in it to hold it released. with the tentioner off the motor still you can very gently loosen the chain slightly on the head thats off timing and actually slip the cam until its in the correct position.

    next re-install the cam chain tensioner and rotate the motor by HAND ONLY!! ( northstars are valve interferent ) you will need to rotate the engine 7 full turns and then check to see if it lines up correctly.

    my 95 did this exact same thing and it turned out to be the rear head intake cam was off 4 teeth!!! once i fixed it it runs great again.

    dont let people here scare you on doing this, it only took me 3 hours start to finish.

    i can give you my cell number if you would like more help, i am not a very good typer...

  9. #8
    1993 eldorado green1's Avatar
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    Quote Originally Posted by chevelle
    Yea, if you are seeing a difference in cranking compression between banks then likely the cam timing is off.

    Given what you have done it is pretty easy to to a quick check. Remove the cam covers or at least loosen them and lift them up enough to see the sprockets. Take out the spark plugs so you can turn it over easily. Turn the engine to TDC number one using a wrench on one of the pulleys of the serpentine belt drive. Stick a piece of wooden dowel down the spark plug hole of number 1 and watch is rise and stop to find TDC quickly. If you put your finger over the spark plug port you can feel compression as the piston comes up to know it is TDC firing.

    Once you have found TDC firing, look at the cam sprockets. The timing marks on each of the sprockets should be at 12:00 relative to the cam cover sealing surface. Use a small pocket square to check that the mark is at 12:00 exactly. If all the marks are at 6:00 then the engine is at TDC but TDC intake/exhaust not TDC firing. In either case, all the marks should be in the same spot. If one (or more) of the sprockets is not in the same spot as the rest and/or not at 12:00 then that cam is out of time.

    The other thing to check is that you have the timing dowels in the cams in the correct slots. The sprockets are common and can be installed on the intake or exhaust cams....but you have to put the timing dowels of the cams into the I or E slot depending on which cam it is for that sprocket. Possibly the timing mark on the sprocket will be correct but the cam dowel pin is in the wrong slot. When the timing marks on the sprockets at at 12:00 relative to the cam cover sealing surface all four cam dowels should also be at 12:00.

    Once you have determined that a cam is out of time you do NOT want to unbolt it and try to move it or the cam chain tensioner will rachet out and stop and you will HAVE to remove the front cover, etc. to reset the tensioner. It is possible to retime the sprockets if you use the correct tools, though, without tearing into the engine again. There is a dealer specific tool that looks like a funny pair of vise grip pliers that is designed to reach down into the chain case at the front of the engine and hold the chain tensioner in place while the sprockets are removed. Since the sprocket has to be removed from contact with the chain and moved a tooth to get it into correct time that is about the only way to do it unless you pull the damper, front cover, etc....and reset the tensioner for that bank.


    the front cover needs to come off eitherway, remember the n-star only lines up every 7 rotations and you will not know if its all lined up unless the front cover is off. its no big deal it took me 3 hours start to finish with your basic garage tools.

    here is the pic link that i made when i did mine,

    http://www.cadillacforums.com/forums...i-thought.html

  10. #9
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    I read through your thread 1993 eldorado green1 and I must say I'm glad you got yours working. However I'm trying to avoid pulling the HB and front cover off. If I mess up it will have to come off.

    I've ordered the tools I need hold the cam chain tensioner and should get them next week. This method all I have to do is remove the valve covers and see which sprocket is off the 90 degree mark. The other advantage from what I've read is the chain tensioner is now set to the correct tension.

    I'm not in a rush the car is in for it's safety inspection now and after I fix the timing it will go for the emissions test.

    I'll post my results and maybe take a few pics when I done.
    Thx 2 everyone who replied.

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    Re: Post Head gasket job (need Veteran rebuilders advise)

    Quote Originally Posted by JaxxMan
    I read through your thread 1993 eldorado green1 and I must say I'm glad you got yours working. However I'm trying to avoid pulling the HB and front cover off. If I mess up it will have to come off.

    I've ordered the tools I need hold the cam chain tensioner and should get them next week. This method all I have to do is remove the valve covers and see which sprocket is off the 90 degree mark. The other advantage from what I've read is the chain tensioner is now set to the correct tension.

    I'm not in a rush the car is in for it's safety inspection now and after I fix the timing it will go for the emissions test.

    I'll post my results and maybe take a few pics when I done.
    Thx 2 everyone who replied.


    you are working on an engine that the timing is already off, i would bet almost anything that you will have to remove the front cover anyway to be able to see the rest of the timing.

    remember you only get 1 shot and you will need new valves, its not worth the risk to save an hours time by not pulling the cover..

  12. #11
    Stoned_Elvis is offline Cadillac Owners Member
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    do you still have that tool? do you want to sell it or rent it out. i need to replace my lifters.


    Quote Originally Posted by JaxxMan
    Found the Tool I need.
    The Kent Moore part Number was invalid in my service manual has been updated to J-38822. I called Kent Moore and they wanted $268.?? for the dam thing.
    I did some more searching and found this tool inside Kent-Moore kit # J-41619 It's labeled "4.0L Engine Overhaul kit" and includes a bunch of other tools I didn't have:
    J-38824-1 Valve Spring Compressor
    J-38824-2 See Above
    J-38820 Seal Remover/Installer
    J-39946 Crankshaft Socket
    J-38822 Timing Chain Holder
    J-39313 Spark Plug Port Adapter
    J-38821 Valve Spring Compressor Adapter
    J-38819 Retainer Remover/Installer

    Found it on e-bay for $125.00 WHAT A Deal !!!!
    At this rate I will have my car fixed before I get 50 posts here.

    Thx for your input earlier chevelle & sts96

  13. #12
    JaxxMan's Avatar
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    Car is running perfect now. I did all the work with hand tools in the parking lot of the garage, without removing the front cover.

    I used a graphite rod to locate TDC on piston one, locked the tool in place and adjusted the sprockets 1 tooth first. I ran a compression test and it went up to 120 psi from 90 before. Locked the tool back in place and moved the sprockets 1 more tool each. Reassembled and ran a second compression test and the psi now matches the back bank of pistons @ 180 psi

    I got the tool on Friday but forgot my camera to take pictures when it was on the car. Here's a pic of the tool.

    There is no way I would sell this tool, it took some work just to get it into Canada. I'm sorry but the only way I would loan it is if you lived in my area.
    Toronto, Ontario area to be specific.
    Attached Images

  14. #13
    Stoned_Elvis is offline Cadillac Owners Member
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    Re: Post Head gasket job (need Veteran rebuilders advise)

    ya i was a day late on ebay. they had one for 175 i believe. but my "alldata" said the part number was j-38815. i called kent moore and they said that the part number changed. by that time it was sold on ebay. i guess ill just take the cover off.

    Quote Originally Posted by JaxxMan
    Car is running perfect now. I did all the work with hand tools in the parking lot of the garage, without removing the front cover.

    I used a graphite rod to locate TDC on piston one, locked the tool in place and adjusted the sprockets 1 tooth first. I ran a compression test and it went up to 120 psi from 90 before. Locked the tool back in place and moved the sprockets 1 more tool each. Reassembled and ran a second compression test and the psi now matches the back bank of pistons @ 180 psi

    I got the tool on Friday but forgot my camera to take pictures when it was on the car. Here's a pic of the tool.

    There is no way I would sell this tool, it took some work just to get it into Canada. I'm sorry but the only way I would loan it is if you lived in my area.
    Toronto, Ontario area to be specific.

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