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Oil consumption ??, compression test results, need advice.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Scooter, Aug 11, 2001.

  1. Scooter

    Scooter 1/2 ton status

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    OK .. first things first .. its an 87 GMC Jimmy 150K+ miles, 350 TBI, 700R4, 3.08 gears, 31-10.50-15's ...

    I just got this truck about 6 weeks or so ago and so far it has been running pretty good. I'm getting an average of 15 mpg driving a mix of about 50% city 50% hwy. The engine always starts right up, warm or cold, and seems to have plenty of power. My biggest concern with this motor is oil consumption. I'm going through about 2 qts of oil per tank of gas. It does puff a very large amount of oil when started after it has sat for more than four or so hours. The only other time I can see any smoke from the exhaust is when I'm really getting on it. And then its black not blue. There are no oil leaks that I can find, nothing on the driveway, the bottom of the engine is bone dry. Also, the inside of the tail pipe is coated with a black sooty residue and the exhaust smells VERY rich. Thinking that my rings are shot and that there is no way that that much oil could be going through the vavle seals that fast I bought a compression tester last weekend. Today I finally did a compression test and here are the results:

    #1 - 140# - spark plug was showing quite a bit of carbon fouling (compared to the others)
    #2 - 140# - spark plug looked very good
    #3 - 135# - spark plug looked very good
    #4 - 135# - spark plug looked very good
    #5 - 140# - spark plug was showing some carbon fouling
    #6 - 140# - spark plug looked very good
    #7 - 140# - spark plug looked very good
    #8 - 130# - spark plug looked very good

    Now as far as I understand this is very good for a 150K+ mile engine and should indicate that the rings are in good shape. Could it be possible that the vavle seals are shot so bad that it would go through 1 qt every 250-odd miles?? How possible is it that the seals are really shot on the exhaust side and oil is flowing out the exhaust and not getting burned causing the sooty residue in the exhaust pipe and lack of fouled plugs? If I can get the tools and parts to change out the vavle seals next weekend should this be something fairly high on the to-do list?

    Also, I know that the EGR vavle is funky on this thing but the local parts store doesnt have one, could that cause the exhaust to smell so rich? How about causing a low idle? I do think that I either need to get new injectors or try to get mine cleaned because it kinda looks more like the fuel is coming out in a stream instead of a nice conical spray. Could that be part (or all) of the rich exhaust smell? The check engine light only comes on when the engine is started for a second or so then goes out (like its supposed to, right?) otherwise it has not come on at all.

    Thanks in advance for any advice or insight.

    Scot in KC, MO.
    <a target="_blank" href=http://www.off-road.ws/images/users/Scooter/side_right_2.jpg>Blue 87 GMC Jimmy</a>
    Red 86 Toyota 4Runner (for sale $2000 obo)
     
  2. ftn96

    ftn96 1/2 ton status

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    All I can add is that it looks like the compression is fair. And they are all even whic his good. The puff at start is definatly the valve seals. As far as how much consumption.??? I have the same problem but my valve cover gaskets are leaking adn I dont have no puddles in the drive either, the oil is getting burned up on the exhaust collector pipe which is unnoticable till the engine is running temp and sitting still.
    As for the black stuff in the pipe, yes, one or more if I read right are not sparking propperly so your getting some un-burned fuel residue left over. YOu have all the symptom of a very well broken in 350. Mine is the same way getting about 15 mpg. 50 50 highway/street..... Hope this helps.....

    Does anyone have a grinding disk I can borrow?[​IMG]3/4 in progress[​IMG]
    <a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>
     
  3. Adrock

    Adrock 1/2 ton status

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    i had the exact same problems. i guess the valve seals in the early TBIs are just real weak. mine would smoke on startup and slowly go away, then come back when i accelerated. i replaced the seals and it fixed the problem. but then i decided to just switch to vortec heads and they absolutely kick ass. i was so affriad at first it was the rings, and i didnt have the type of money to replace rings. but it was only the valve seals. hope everything works out for ya. good luck.

    Adam
    a.k.a. Adrock
    88 Chevy Blazer FI 383
    "With great power there must also come great responsibility" -Spiderman
    "Juggernaut Smash" -Juggernaut
     
  4. CaptCrunch

    CaptCrunch 1/2 ton status

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    FYI...
    Same deal here Scoots... My valve seals leak like a son of a gun. Motor at about 145k. Big puff of smoke after most stops and if it is idling for a long time and I nail it it smokes... my compression is in the same range as yours. I plan to just do the whole motor cause ain't no way I'm gonna do seals or a head job w/ my lift. Mine sucks a good qt and a half every thousand id say.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</a>
     
  5. ftn96

    ftn96 1/2 ton status

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    LOL!!! Yeah after idling for a while....Like driving in bumper to bumper traffic and the people stuck right next to your tail pipe must be hating life. I fumagated someones car for them the other day and they pulled up beside me all cussing and (s)hit telling me I need to get my motor fixed....LOL!!! I said it wouldn't do that if they got the freaking roads fixed where all this traffic wouldn't happen...[​IMG]

    Does anyone have a grinding disk I can borrow?[​IMG]3/4 in progress[​IMG]
    <a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>
     
  6. Scooter

    Scooter 1/2 ton status

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    Thanks for the feedback guys!! I think I'm gonna borrow the tools and get the parts to try replacing the seals next weekend. Hopefully that will at least slow it down some. Any particular type or brand to get or avoid for the seals? Anybody else have any ideas?

    Thanks again

    Scot in KC, MO.
    <a target="_blank" href=http://www.off-road.ws/images/users/Scooter/side_right_2.jpg>Blue 87 GMC Jimmy</a>
    Red 86 Toyota 4Runner (for sale $2000 obo)
     
  7. ftn96

    ftn96 1/2 ton status

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    Every serious gear head I've ever talked to sai to get the "umbrella" type valve seals. This is one of the things on my to do list. Till then I just keep dumping oil in.

    Does anyone have a grinding disk I can borrow?[​IMG]3/4 in progress[​IMG]
    <a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    O2 Sensor is what controls the mixture. They are supose to be replaced every 60k. When they go bad it usualy makes them go rich. The rich condition will get some fuel into the oil thinning it out making it more prone to evaporate so it is adding to your consumption.
    Majority of your consumption is still the vavle guide seals. Cat's tend to help hide oil burning. It reburns the oil so less smoke.
    You one bad plug may indicate that cylinder in particular has high consumption. Probably find the intake side seal is cracked on that one. Might also have a plug wire problem on that cylinder and getting a slight missfire.
    Over all the compression numbers sound great for the miles. Bottom end seem pretty healthy.

    It's not my damn planet monkey boy!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>

    Grim-Reaper
     
  9. Scooter

    Scooter 1/2 ton status

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    Well, I got my parts for this weekends projects: new valve seals (supposedly a newer umbrella style), valve cover gaskets, O2 sensor, a Hayden rapid-cool plate style tranny cooler rated for class "A" motorhomes towing upto 10,000# (think that'll be big enough), fuel filter, and some new taylor plug wires. There goes another $130 to O'Reillys, my new second home. Hopefully when I'm done that will help get rid of most of the problems.

    Any pointers from anyone thats replaced valve seals while the head is still on the engine?? I think I have a pretty good understanding of how to do it, just looking for some tips and tricks from the pros.

    Scot in KC, MO.
    <a target="_blank" href=http://www.off-road.ws/images/users/Scooter/side_right_2.jpg>Blue 87 GMC Jimmy</a>
    Red 86 Toyota 4Runner (for sale $2000 obo)
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I have the same Hayden cooler on both my trucks. NEVER gets above 175 on the tranny. The 175 was pulling my moms car 200 miles back from Knoxville with 3.08 gears and 32 inch tires. Got on a REAL long hill that semi's were dropping down to 45 mph on and it hit 175. was back down to it's normal 160 about a mile after I crested the hill.
    As for the seal change....I like the rope in through the plug hole way. I have done bleed down tests a few times and it's darn hard to get the piston right on tdc so the motor doesn't spin. My fear would be dropping the valve in the cylinder if the motor spun and opened the other valve.
    With feeding some rope in you have the piston holding the valve up and if you want to take a break it will hold till you spin the motor so basicly till the end of time. I like the umbrella style seals. The o ring style just don't seem to hold up as well.
    As far as what it cost...heck that's a lot less than a car payment and your not going to need to do it again for a long time. Wait till you go through the front axle...you can eat up $500 if you do it all (ball joints, seals, tie rod ends, etc) real quick.

    It's not my damn planet monkey boy!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>
    75 Jimmy, Dollar
    79 Chevy Blazer, Her's
    70 Chevy Burb
    Grim-Reaper
     
  11. Scooter

    Scooter 1/2 ton status

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    Good deal on the cooler. I figured it would be more than enough to get the job done.

    I was only joking about the $$ I've spent there. I know its lots cheaper than a car payment. So far I've managed to spend about $130 every other week at O'Reillys. I'm not complaining, it really helps when one of my step-brothers is the manager.

    I do have a question about the rope deal. I've now heard 2 people say something about that but I have never heard of it. Is it just a matter of getting it as close to TDC as possible and then stuffing rope in through the spark plug hole? If so, that would probably be a smarter choice to do instead of using compressed air. The valve seals are supposedly a "new and improved" version of the umbrella style seal. Its looks like the regular umbrella seal except that it has what looks like a steel spring clamp around it too.

    Basically I've been doing things to it every weekend. Last week was the compression test and some odd and ends. Two weeks ago Greg (Prembird) and I did both of the tie rod ends and the rear u-joint. The week before was Warn hubs. Before then was some rust repair and rattle can paint on the roof. You get the idea, just doing a little at a time. Its kinda slow going but it's getting there.

    Scot in KC, MO.
    <a target="_blank" href=http://www.off-road.ws/images/users/Scooter/side_right_2.jpg>Blue 87 GMC Jimmy</a>
    Red 86 Toyota 4Runner (for sale $2000 obo)
     

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