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1998 GMC 5.7 Vortec - Front oil seal leak?

This is a discussion on 1998 GMC 5.7 Vortec - Front oil seal leak? within the Technical / Maintenance forums, part of the General Discussion category; So my trucks been dripping some oil for quite some time now at the front of the motor and it ...

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    1998 GMC 5.7 Vortec - Front oil seal leak?


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    So my trucks been dripping some oil for quite some time now at the front of the motor and it would land on the sway bar and hit the ground. I just changed my oil and the leak got 2x worse than before. It's getting more annoying than anything else. Making my driveway look bad. I'm thinking the new / thinner oil seeping through easier. Is this the seal under the timing chain on the front lip of the oil pan and not the oil pan gasket itself? Rubber if I remember. Is this a pretty easy fix? Any tips / tricks to get this done? I've already replaced the lower intake gaskets w/ the steel inserted gaskets from GM. Is this pretty common on these motors or not?

    Thanks,
    Last edited by 98GMC84; 04-11-2012 at 09:05 AM.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    If it is the timing case cover gasket, you will need to remove the front two oil pan bolts as well. As for the driveway, most "cleaners" on the market will not do a good job of removing the oil stain. Get some cardboard boxes from local grocer, place under truck when you park it. ( I've used 4-6 4" red bricks to hold it down in wind.)
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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    If you have the plastic timing chain cover I'd replace it as well. make sure its not your oil cooler lines too...

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    If you have the plastic timing chain cover I'd replace it as well. make sure its not your oil cooler lines too...
    My truck doesn't have an oil cooler. Is this normal? I noticed this when I replaced the radiator... I just know that this leak is getting worse and needs to be fixed soon.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Depends on the model and package options I would assume , could very well be normal ( towing/off road pkg).. you will prabaly have to loosen the pan a bit depending on how thick the new gasket is..dont pry or hammer the timing cover back on..lower the pan to do correctly (if need be)
    Could also be the cranck shaft seal...
    Last edited by 96Z71Siverado; 04-11-2012 at 11:51 AM.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Just crawled under the truck on my break. Definately coming from the bottom of the timing cover. The rubber seal between the pan and timing cover, is this a normal place for these to leak? 128,000 miles on it. How exactly do you replace it? I have the balancer puller. Do I even need to pull the timing cover if i drop the pan a little bit? How many other guys had these leak at this location. My neighbor seems to think that its not it... He said something about the secon bolt hole over where the battery is grounded. He thinks there should be a bolt there because it goes right directly to the oil gallery. I don't have a bolt there and it's dry and rusted around that area.

    Thanks,

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    that seal is actually the oil pan gasket.. the proper way would be to drop the pan and replace the pan gasket.. problem solved...if thats whats really leaking...Clean it off and watch it to be sure...

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    that seal is actually the oil pan gasket.. the proper way would be to drop the pan and replace the pan gasket.. problem solved...if thats whats really leaking...Clean it off and watch it to be sure...
    I'm almost positive that's it. But it's only wet at the bottom of the timing cover. Could I do the gasket without removing the timing cover? That would save alot of time. Not sure if the plastic timing cover is a wear item or not.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 98GMC84 View Post
    I'm almost positive that's it. But it's only wet at the bottom of the timing cover. Could I do the gasket without removing the timing cover? That would save alot of time. Not sure if the plastic timing cover is a wear item or not.
    So what is the easiest / best way to approach this?

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    If you got the room to do it, replace the pan gasket..IMO
    Im sure some other people will tell you different, Im a mechanic, and this is what I would do if it were my vehicle. (As long as your positive the crank seal isnt leaking)
    Last edited by 96Z71Siverado; 04-12-2012 at 08:33 AM.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    If you got the room to do it, replace the pan gasket..IMO
    Im sure some other people will tell you different, Im a mechanic, and this is what I would do if it were my vehicle. (As long as your positive the crank seal isnt leaking)
    Thanks for the reply. How can I tell the difference between the pan gasket and crank seal? What all goes into changing a crank seal? I've never done one of those before. The entire pan is dry except up front under the timing cover which is wet with oil. I just want to do this once. How rare is it for a pan seal to leak vs a crank seal to leak on a vehicle w/ 126,xxx miles?

    Thanks

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    is the 5.7 a 350? ive worked on a couple and the seals are seperate from the oil pan gasket itself in the kits ive used, just scrape all gasket off and put some oil restant rtv on mounting surface then put gasket on then put some rtv on each end of the gasket and put oil pan back on

    i think this is the gasket your talking about

    i did 3 of em with engines out of truck so not sure what it would be like inside truck
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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 98GMC84 View Post
    Thanks for the reply. How can I tell the difference between the pan gasket and crank seal? What all goes into changing a crank seal? I've never done one of those before. The entire pan is dry except up front under the timing cover which is wet with oil. I just want to do this once. How rare is it for a pan seal to leak vs a crank seal to leak on a vehicle w/ 126,xxx miles?

    Thanks
    Well, its gonna take some good cleaning skills and some patients..get some brake clean and a rag, and you need to clean off all the residual oil from the problem area, as well as up behind the damper as close to the crank seal as you can.. once you have it spick and span..then fire it up and watch it to see where it starts to seep from..thats about all you can do..it would really suck to go thru all that and not fix the right thing.. so be sure whats leaking before starting.. And if it were my truck, and it turned out to be the crank seal, I would still do the pan gasket anyway...(if it were me)

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    Well, its gonna take some good cleaning skills and some patients..get some brake clean and a rag, and you need to clean off all the residual oil from the problem area, as well as up behind the damper as close to the crank seal as you can.. once you have it spick and span..then fire it up and watch it to see where it starts to seep from..thats about all you can do..it would really suck to go thru all that and not fix the right thing.. so be sure whats leaking before starting.. And if it were my truck, and it turned out to be the crank seal, I would still do the pan gasket anyway...(if it were me)
    So is there three seals? Oil pan. Timing cover. Crank Seal. Where exactly is the crank seal and how would I get to it? When I clean everything off and start to watch, how do you tell the difference between a leaking crank seal or the bottom of the timing cover? How does the crank seal attach / remove?

    Thanks,

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    the crank seal is behind timing gears if im not mistaken or might be part of timing cover
    2002 silverado 1500 extended cab short bed 5.3L

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    The crank shaft seal is behind the Harmonic Damper, and pressed into the timing cover, its what keeps the oil in the engine at the point the crank shaft nose sticks through the timing cover..its round, and the damper spins on the seal just like an axle seal or a pinion shaft seal, sector shaft seal..etc..
    the surface of the harmonic damper that rides on the seal can wear down over time..some crank seal kits come with a sleeve to install over the end of the damper nub to bring it back to spec..Ive personally never had to use it, but yours may need it..
    If its the crank seal thats leaking, it will drip down above the lower timing cover seal, onto the lower seal, thats how you can tell, but if the space between the crank seal and the lower cover seal is dry and its obviously spitting oil at you at the bottom then theres your smoking gun..
    Also just an FYI..the key way in the crank can be a oil leak source too...
    Last edited by 96Z71Siverado; 04-12-2012 at 11:34 AM.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by Chevy53 View Post
    is the 5.7 a 350? ive worked on a couple and the seals are seperate from the oil pan gasket itself in the kits ive used, just scrape all gasket off and put some oil restant rtv on mounting surface then put gasket on then put some rtv on each end of the gasket and put oil pan back on

    i think this is the gasket your talking about

    i did 3 of em with engines out of truck so not sure what it would be like inside truck
    Quote Originally Posted by Chevy53 View Post
    the crank seal is behind timing gears if im not mistaken or might be part of timing cover



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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    The crank shaft seal is behind the Harmonic Damper, and pressed into the timing cover, its what keeps the oil in the engine at the point the crank shaft nose sticks through the timing cover..its round, and the damper spins on the seal just like an axle seal or a pinion shaft seal, sector shaft seal..etc..
    the surface of the harmonic damper that rides on the seal can wear down over time..some crank seal kits come with a sleeve to install over the end of the damper nub to bring it back to spec..Ive personally never had to use it, but yours may need it..
    If its the crank seal thats leaking, it will drip down above the lower timing cover seal, onto the lower seal, thats how you can tell, but if the space between the crank seal and the lower cover seal is dry and its obviously spitting oil at you at the bottom then theres your smoking gun..
    Also just an FYI..the key way in the crank can be a oil leak source too...
    Bingo!

    i say just pull off the balancer, remove the timing cover and oil pan, replace oil pan gasket (use a good one piece), timing cover gasket and the crank seal.



    the crank seal is the seal where the big hole in the cover is, the "Snout" of the crank pops through that, the balancer gets pressed onto the crank, sealing itself on the crank seal.
    Last edited by BlacK20; 04-12-2012 at 11:48 AM.


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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by BlacK20 View Post
    Bingo!

    i say just pull off the balancer, remove the timing cover and oil pan, replace oil pan gasket (use a good one piece), timing cover gasket and the crank seal.



    the crank seal is the seal where the big hole in the cover is, the "Snout" of the crank pops through that, the balancer gets pressed onto the crank, sealing itself on the crank seal.
    Couldnt of said it better myself..:)
    Last edited by 96Z71Siverado; 04-12-2012 at 01:06 PM.

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    Re: 1998 GMC 5.7 Vortec - Front oil seal leak?

    Quote Originally Posted by 96Z71Siverado View Post
    Couldnt of said it better myself..:)
    Great information here. My last question is this. Does the new timing cover (dorman, etc) come with the crank seal with it? Or is it a separate piece? I take it I have to pull the fan and waterpump for this... Just put new coolant in this thing... Could I get this done on a Saturday? I've done lower intake gaskets over a full days work.

    Thanks!
    Last edited by 98GMC84; 04-12-2012 at 02:51 PM.

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