97 STS, low compression in all left bank cyls
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 3 1 2 3 LastLast
Results 1 to 15 of 32
Northstar Engines and System Technical Discussion Discussion, 97 STS, low compression in all left bank cyls in Cadillac Engine Technical Discussion; The car I'm looking at is a 97 STS, 111K, $3K. Car was in this shop for head gasket job; ...
  1. #1
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    97 STS, low compression in all left bank cyls

    The car I'm looking at is a 97 STS, 111K, $3K. Car was in this shop for head gasket job; they sent block/heads out for repair ($800 !), then they gave car back to owner. Owner drove it for 2 weeks, then had it towed in with 'no power' complaint. Since owner had not and could not pay for first repairs, service shop became owner. They're selling to recoup their $$.

    So I looked at car and it's great in/out. Engine ran, real rough at first, no response to acc pedal at all. Sounded like exhaust manifold leak, misfires. Had to start it 3-4 times (trying to warm it up for compression test). I was able to rev up a bit, and engine ran a lot smoother, very little smoke at pipes, still heard what sounded like exh leak. No big knocks frmo bottom (good news, I hope).

    I did a comp test; found ~210 PSI (120 on first stroke) on the right (rear) bank, and 180,170,180,160 PSI (90 on first stroke) on the left (front) bank. When I tested the front 4, there was a 'pop' noise during each turn of the engine. But when I tested the rear 4 (all ~210PSI), there was no pop.

    So, I think the front head is loose (or big time gasket malfunction) since all 4 cylinders read low and each cylinder produces the pop sound during compression testing. I have to wait until Monday to learn exactly what the machine shop did (helicoils? Timeserts? All holes, or just some holes, etc.).

    My first question is: Can I get a shop to timesert the left (front) bank while it's in the car? Or is that a foolish thought? (I'll look for a different shop, unless the first wants to do it for free and I can find someone who can vouch for this shop's expertise in N*.)

    2nd question. Assuming I pull the engine, what do I do with the right (rear) head. Leave it on? If I have to take it off, should I get those holes timeserted if they weren't done before? I know other threads suggest doing all holes if you're doing one, but the head is working great as is.

    Your replies are much appreciated.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003
    Location
    Arizona
    Posts
    3,531

    Re: 97 STS, low compression in all left bank cyls

    First, this is the wrong section for questions. It's for tips. Ranger will probably move it to the N* section.

    I'd ask the shop whether they timeserted all the holes. Then I'd remove the front head and see if they really did. I would also pay attention to the tightness of the headbolts. It's possible they missed one whole tightening sequence and under tightened. You'd have to replace the bolts and gasket again.

    If all the holes were timeserted I'd leave the back head on and cross my fingers.
    We got interupted on one by a phone call and weren't sure where we stopped, so we redid them all (which is OK). It's possible the mech got interuppted and mised a tightening sequence. You can't really check that.

  4. #3
    EcSTSatic's Avatar
    EcSTSatic is offline Cadillac Owners Connoisseur
    Automobile(s): 1999 STS - diamond white
    Join Date
    Dec 2004
    Location
    Wichita, KS
    Posts
    4,523

    Re: 97 STS, low compression in all left bank cyls

    With the popping. misfires. power loss etc, it sounds like they didn't get the cam timing set right when they fixed the head gasket. Or it slipped.

  5. #4
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    Re: 97 STS, low compression in all left bank cyls

    Quote Originally Posted by zonie77
    First, this is the wrong section for questions. It's for tips. Ranger will probably move it to the N* section.
    Ok, sorry. I wasn't sure, as I did see other qs here.
    Quote Originally Posted by zonie77
    I'd ask the shop whether they timeserted all the holes. Then I'd remove the front head and see if they really did. I would also pay attention to the tightness of the headbolts. It's possible they missed one whole tightening sequence and under tightened. You'd have to replace the bolts and gasket again.
    I'm calling them Monday morning. If this is all I need, I'll be one happy dude.
    Quote Originally Posted by zonie77
    If all the holes were timeserted I'd leave the back head on and cross my fingers.
    We got interupted on one by a phone call and weren't sure where we stopped, so we redid them all (which is OK). It's possible the mech got interuppted and mised a tightening sequence. You can't really check that.
    If the bolts are tight when I remove them, and the timeserts are there (what do installed timeserts look like?), I'll replace the gasket and bolts and fire her up. This should cover a defective gasket (unusual?) or incorrect tightening. What else could have caused this - more overheating that was not fixed before or after the head work?

    If the holes were not timeserted, is it possible to timesert the front headbolt holes with the engine still in the car? This would obviously save a lot of work. (I did a Helicoil on a 1984 Buick Electra wagon - engine still in the car - with a busted headbolt - worked great).

  6. #5
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    Re: 97 STS, low compression in all left bank cyls

    Oh - forgive my apparent ingratitude. Thanks for the quick replies and the great info. Although I've already given a small amt to maintain this site, I've decided that if I buy and then sell this car, I'll donate 5% of the profit to this site. Hopefully that will be more than a few $$.

  7. #6
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    Re: 97 STS, low compression in all left bank cyls

    Thanks for the reply!
    Quote Originally Posted by EcSTSatic
    With the popping. misfires. power loss etc, it sounds like they didn't get the cam timing set right when they fixed the head gasket. Or it slipped.
    Well, it ran for about 2 weeks with no problems, so they must have initially set it right. I'm hoping these symptoms are purely due to the 'loose' head.

    But, now that I've thought a bit more, if it ran OK for 2 weeks, doesn't that mean that the head was correctly installed? Or, maybe the gasket held for 2 weeks under bad install conditions, and then finally failed?

  8. #7
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003
    Location
    Arizona
    Posts
    3,531

    Talking Re: 97 STS, low compression in all left bank cyls

    A timeserted hole looks different than a stock hole. Look at the timesert website. Look at the N* head gasket thread in this section for timesert info.

    I agree that cracked or warped head shouldn't effect all 4 cyls the same (assuming it ran well at first). Cam timing shouldn't have jumped unless the chain guide came loose. Slim possibility.

    Are you familiar with tightening procedure? 30ft/lb, then 70deg,+70deg,+70deg (I think). Since you're not using a torque wrench you have to measure the amount it turned (gauge available at Azone). If you goof and miss 1 series you left them very undertorqued. If the mech got interupted he might've missed 1 sequence and not realized it. I'd give that the most likelyhood.

    You can do this in the car but the cam timing is hard to do with the limited room.

    You must use new bolts too.

    You could try just tightening the bolts and see what happens (see how tight they are,then loosen and redo tightening procedure). If they all retighten and it runs good you know what's the problem. I'd still replace the gasket and bolts but you would have verified the problem! If any won't tighten you've got a thread problem.

  9. #8
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    Re: 97 STS, low compression in all left bank cyls

    Quote Originally Posted by zonie77
    Are you familiar with tightening procedure? 30ft/lb, then 70deg,+70deg,+70deg (I think).
    Alldata says 30, then 60,60,70. But I think I remember seeing a change to that - I think the initial 30 was dropped to the low 20s ?? I can't recall where I saw this. Help anyone?

    Quote Originally Posted by zonie77
    You could try just tightening the bolts and see what happens (see how tight they are, then loosen and redo tightening procedure).
    How do I 'see' how tight they are? Is there a certain torque 'range' that properly tightened bolts will meaure at? Should I just try torquing to - 75 (a safe number?)- and then call them tight if they don't move?

    Quote Originally Posted by zonie77
    If they all retighten and it runs good you know what's the problem. I'd still replace the gasket and bolts but you would have verified the problem! If any won't tighten you've got a thread problem.
    Need your opinion in this: I guess if I'm going to replace the bolts and reassemble to test, I may as well remove the head, inspect the holes, change the gasket and bolts, and then bolt everything back together. I think the only extra step is to lift the head and put in a new gasket. It's one less tightening sequence on those head bolt holes, which sounds like a good thing to me. I won't know for sure it was 'just' loose bolts but I'll settle for knowing it was either 'loose' bolts or bad gasket (which I can at leats visually inspect, right?).

  10. #9
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003
    Location
    Arizona
    Posts
    3,531

    Re: 97 STS, low compression in all left bank cyls

    Did you disassemble it? My suggestion to tighten the bolts assumed it was still together. That would let you confirm it was just loose bolts without a lot of work.As far as tightening them to some torque value for a test, sure 75 lbs would be about right, for a test I'd probably just go 60. This is for a test. I'd do the correct tightening seq for the new bolts.

    Once the bolts are heatcycled more than a few times they must be replaced.

    If the bolts were loose but the threads good I'd try replacing the bolts without replacing the headgasket. We had a Caddy engr on here before and he even said that the plant does that on test engines. A new gasket should still be resiliant enough to handle that. If that happens you should run out and buy a lottery ticket!

    (I heard that the 99's and 2000's had that problem and guys at the dealerships were grabbing them and changing the bolts without changing gaskets. Just a rumor from a Caddy employee I dealt with)

    The tightening seq I gave was from memory, that's why I put (I think) next to it.

    Testing the bolts (if they are soooooooooo loose the head is lifting on compression) should be obvious with a ratchet. If you need a breaker bar they are probably not be the problem.

  11. #10
    dkozloski's Avatar
    dkozloski is online now Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,095

    Re: 97 STS, low compression in all left bank cyls

    I'm betting on a cam timing issue.

  12. #11
    mcowden is offline Cadillac Owners Connoisseur
    Join Date
    Jun 2003
    Posts
    1,164

    Re: 97 STS, low compression in all left bank cyls

    Quote Originally Posted by dkozloski
    I'm betting on a cam timing issue.
    That's what it sounds like to me, too. Where you been hiding, dkozloski?
    Mike

  13. #12
    chevelle is offline Cadillac Owners Enthusiast
    Join Date
    Jul 2005
    Posts
    510

    Re: 97 STS, low compression in all left bank cyls

    Since this whole thing started with the teardown and it affects an entire bank of cylinders I am betting on a cam timing issue also. Hard to visualize a head gasket affecting all 4 cylinders like that.

    It is somewhat easy to check the cam timing. Number 1 is on the right front corner of the engine. Passenger side, rear bank. Take the plug out. Stick a wooden dowel down the spark plug hole and turn the engine until you find TDC when the dowel stops moving and reverses direction. Take the front cam cover off or loosen it enough to lift the front end up. The cam timing marks on the sprockets should be at 12:00 relative to the cam cover sealing surface of the head. Look at the cam sprocket marks and timing slots. The slot on the pin of the intake (inboard) cam should have the LI marks by it (left intake...get it??) and the exhaust cam sprocket should have the timing slot marked LE over the timing pin of the exhaust (outboard) cam. If the marks are at 6:00 then the engine is at TDC exhaust. Turn it one more time to check the timing. The sprockets are identical and installed on the intake and exhaust cams per the LI and LE marks. Maybe they just got them mixed up.

    The owner may have not know the difference when they got the car back that it wasn't running right until they drove it awhile and then wouldn't pay because the repairs did not go right.

    You need to quiz the shop about the work done. They would know if they installed timeserts into the head bolt holes or not. If they cannot answer that question or do not know what timeserts are or used helicoils then walk away.

    Ask them if they pulled the heads off without taking the front cover of the engine off. To reset the cam chains correctly the front cover needs to come off...if nothing else to reset the cam chain tensioners.

    If the car ran OK for awhile and then started this possibly they let the cam chain tensioners rachet out when they took the head off and then FORCED the cam chains back onto the sprockets. This would eventually cause failure of the cam bearing, front of cam, sprockets, guides, chain, who-knows-what.

    In a deal like this it is impossible to predict what you are getting into. With an independent shop working on an engine that they may have had no previous experience with anything could have happened. In any case, assuming it is the head gasket again is a bit premature and unlikely in my estimation.

    Ask the shop if they have a service manual for the engine. That might be the first clue as to whether the repairs can be relied on or not.

    In any case, sounds like a potential $$$$$$ nightmare to recover from what they have done. Replacing a head gasket and timeserting the head bolt holes is not that difficult a task, really, if you can read and follow directions.

  14. #13
    jkk
    jkk is offline Cadillac Owners Member
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    50

    Re: 97 STS, low compression in all left bank cyls

    Here's an update;

    Zonie77: It's still assembled, sitting on the repair shop's parking lot. I'm still trying to decide if I should buy it. The repair shop's owner and mechanic have been really helpful, understandably so since I think they're trying to get paid for their work changing the head gasket and the $750 they paid for machine work.

    Let me setup the original scenario: Original problem was with the front head. They fixed it. Mechanic said this was the second time to have the head bolt threads fixed and they used the bigger inserts (from GM). Owner drove it for ~2 weeks, came in with "loos of power". Since owner had not paid for previous work ($3K), the service guys just parked it on the lot. They never even read codes or did a compression test. They'd just like it gone. They gave him 1-2 months to pay. Since he didn't, he gave them the title. They're selling it to recoup their investment.

    I'm encouraged to hear the timing comments from dkozloski and mcowden. This is why.

    I just saw the car again 2 hours ago. I asked them to scan for codes - all we got was an ICM ground code error (or fault?) on his scan tool (red box). Then we couldn't scan anymore as his scanner wouldn't connect again. He couldn't figure out why.

    Also, I was thinking more about the compression test I did. Results were ~210 PSI (120 on first stroke) on the right (rear) bank, and 180,170,180,160 PSI (90 on first stroke) on the left (front) bank. Although these are lower than the rear and somewhat unsettling since this head was the original culprit, the numbers don't have to be caused by a headgasket, do they? Would the timing issue lower all 4 readings, or should it lower some and raise others? How can I discern - before I give them $3K - that it's most likely an ignition (timing) issue and not a head gasket?

    thanks.

  15. #14
    EcSTSatic's Avatar
    EcSTSatic is offline Cadillac Owners Connoisseur
    Automobile(s): 1999 STS - diamond white
    Join Date
    Dec 2004
    Location
    Wichita, KS
    Posts
    4,523

    Re: 97 STS, low compression in all left bank cyls

    A timing issue will drop the compression on all cylinders because the valves are not closing competely on the piston's upstroke. Also, your ignition will fire at the wrong times causing "popping" sounds because the valves are not sealing the chamber.
    That's why that was the first thing to come to my mind when you mentioned the symptoms. (see third post)
    There should be alignment marks on the cam sprocket to help you determine if it is right of not.

  16. #15
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003
    Location
    Arizona
    Posts
    3,531

    Re: 97 STS, low compression in all left bank cyls

    Quote Originally Posted by jkk



    Also, I was thinking more about the compression test I did. Results were ~210 PSI (120 on first stroke) on the right (rear) bank, and 180,170,180,160 PSI (90 on first stroke) on the left (front) bank. Although these are lower than the rear and somewhat unsettling since this head was the original culprit, the numbers don't have to be caused by a headgasket, do they? Would the timing issue lower all 4 readings, or should it lower some and raise others? How can I discern - before I give them $3K - that it's most likely an ignition (timing) issue and not a head gasket?

    thanks.

    We are talking Cam timing, not Ignition timing.


    Cam timing could effect one head as each head has separate cams.

    All the guys betting on cam timing could be right. It wouldn't be that hard to fix if nothing was damaged. Even if a chain or tensioner was ruined they aren't that hard to change. You check the cam timing with the valve covers off. I think you could do it with the timing cover still on.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting