Thoughts on 1998 Z71??

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Thoughts on 1998 Z71??

Postby cackler » Fri Aug 03, 2007 3:06 pm

I am looking for a full size pick-up for this year. A dealer has a 1998 GMC Z71 with 101000 miles. What types of problems have any of you had with theirs? It has the 5.7 vortec, so what can I expect as far as gas mileage? I average about 13000 miles a year so do you think it will last untill I get out of college in 2-3 years? I was thinking about geting a 2001-2003 but the more I think about it, I dont really want to spend 250 a month while I am still in college and I can trade my Ranger straight accross for this truck which equals no monthly payments.
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Postby fowl_wishes » Fri Aug 03, 2007 4:48 pm

That truck with that engine has a lot of pattern failures.

1) Leakin gintake gasket -- will either leak coolant internally (most likely) or internally. and in a few cases they will leak vacuum to the crank case and cause a misfire. If it is leaking coolant externally, you can see the coolant slowly seeping out from under the intake jsut behind the water pump. If it is internal the inside of the oil fill cap will be milky looking. if the leak is vacuum, it will have a rough idle and load misfire

2) Oil cooler lines if equipped. They are terrible about leaking. Replace to fix.

3) Heater hose quick connect. They WIL BREAK!!! and they are a pain in the but to replace. Normally they do not jsut break off, they normally have to be hit or the hoses have to be pulled. The threads break off in teh intake. Which mean you have to get it out with a hammer and chisel (and a tap if you are lucky). They make newer style that are made out of a harder corrosion resistant material. This should be replaced if you see "brown sugar" residue around the fitting.

5) The central sequential fuel injection system is prone to small fuel leaks under the upper plenum. The injectors are centrally located with a tube and a poppit valve feeding the cylinder. These poppit valves will slowly leak over time causing a check engine light to illuminate (usually a Bank rich doe or O2 sensor code depending). The fuel pressure regulator is also mounted under the upper planum. This piece is known to leak after a lot of miles. It will dump raw fuel into the engine (usually cylinder 4 or 6) causing a misfire or check engine light (see above reason)

6) Like ALL chevy trucke the steering components (pitman arm, idler arm, tie rod ends, ball joints) need to be checked. With that mileage it is possible (likely) they some of the parts need replacing if they have not already.

7) The front axle disconnect motor goes out fairy often if the truck is used in 4x4 much (of if the trucks runs in a lot of water). The original piece uses a bi-metallic strip but a new style uses a true electric motor. They both fail, and the original bi-metallic is a lot cheaper.

That is all i i can think of off the top of my head. Not tryin to scare ya partner. You asked and i am tellign what i see on a daily basis at my shop. The trucks are GREAT vehicles if they have been taken care of. with those miles you should be able to get another 100k out of it pretty easy if it is in good order. I have seen A LOT of those trucks ragged out, but still on teh road.
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Postby cackler » Fri Aug 03, 2007 6:41 pm

Thats what I wanted to know, Thank you. :thumbsup: I think I may just buy a newer one so I can get a good full coverage warranty.
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Postby fowl_wishes » Fri Aug 03, 2007 7:01 pm

That decision is up to you partner. wasnt trying to turn you away from the truck. In the end it is whther you want to spend money EVERY month on a payment, or cash here and there for repairs.
Shoot'em close. Less to pick.

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Postby cackler » Sat Aug 04, 2007 5:39 pm

No, you didnt turn me away from it. I talk to a mechanic today at work about it and he pretty much gave me your list plus a few more things, including issues with the transmission and body. I am just not sure if I would want to take an older truck to Nebraska two times a season pulling my 6x12 trailer the more I think about it.
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Postby fowl_wishes » Sat Aug 04, 2007 6:53 pm

Yea i forgot to mention all the rusted cab corners. :yes:
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Postby ksgooser » Sat Aug 04, 2007 11:24 pm

My uncle has one and he has had to put in one tranny and several other things and is about ready for another tranny again. Everyone that I have talked to about them have said that the tranny just plain sucks.
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Postby Sailor » Thu Sep 27, 2007 1:55 pm

I wish I still had my '98 Z71 xcab. I sold it last summer with 230k miles, it still averaged 17 mpg and didn't smoke at all. I replaced a transmission at 160k, a couple sets of tires, brakes, an intake gasket and the alternator (~60k miles). It was one of the best trucks I have ever owned and the only one I bought new. I now have a 2004 Z71 crew cab. I absolutely love the crew cab and other creature comforts, like fog lights, built in satellite radio, computer, etc. but this truck has ZERO low end pick-up. You have to give it enough gas to downshift the transmission in order to move anywhere faster then a snail and the mileage is just about the same.
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Postby hurricane658 » Fri Nov 30, 2007 12:55 pm

Im with the guy above me! I have one almost identical to the one you were looking at and I love it. No problems with the transmission and I'm in the mud quite often. I had to replace the fuel pump last year but other than that, its been one helluva truck. I will never own any product as long as I live besides a GM.
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Postby flocknockerpa » Sat Dec 29, 2007 6:10 am

I had a 97 Sierra Z-71, I loved the truck and would have kept it but needed more room with 3 kids the extended cab is no good even with the 3rd dr when you have car seats. I had 130,000 miles on it when I traded it in and did the basic repairs, alternator, brakes, idler arm and intake gasket.....Other then that ran synthetic oil in it since pretty much day one, no smoking or oil burning or leaking and changed the oil every 5,000 miles. Could have gotten more on a private sale then the $6,000 they gave me on a trade but when you only pay $24,000 after rebates, discounts and trade for a new 07' its hard to pass down........ :thumbsup:
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Postby buckshot1224 » Wed Jan 23, 2008 5:30 pm

I have a '99 Z71 ext cab and LOVE it. It is the old body style like the '98. It has the 5.7L and the only major trouble I have had out of the engine was the intake gasket. For what I understand most Chevys from those years have trouble with the intake gasket and according to a recent lawsuit against Chevy it is due to the red antifreeze. Don't know if that is true, just saying. My truck runs the yellow now and I have had any trouble. I have a lifter that is starting to leak down with the truck sits for a day or so but other than that everything is fine.

Mine has 140K miles and I've worked it hard. I live on a farm an it has seen 6 ton sprayers, 4500lbs of hay hauling and 200 miles on many occasions, I've even pulled a 450C Dozer with it (only about 3 miles). I've heard a lot of the same lists that have been mentioned but unless you buy new with a warranty, it doesn't matter the make, it happens. Good Luck!!
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Postby pike_mazter » Wed Mar 12, 2008 10:56 am

I own a 98 Z71 sierra. Best vehicle I have ever owned! Sure it has its problems, but what truck doesn't?

I get 17-19 MPG City and Highway. No really I do. I run only 93 or 94 octane.

I have a K&N filter. Throttle body spacer. 93 Octane chip. Trans cooler, flex fan flowmasters and many more add ons. Its been good to me so far. It was well taken care by previous owner and it shows. 350 5.7 vortec is FAST, well at least with the add ons. I have raced a buddy in his Ram Big Horn with the Hemi and smoked him! (he really doesn't know how to drive, if we would of switched vehicles I would of beat my own truck in his) After 3,000 miles my oil is still clear, no really it is. Once the weather clears I'll throw some pics up.

The front end including steering has all been replaced and only has 10,000 on those parts. Truck has 100,000 miles and the tranny is as strong as it was when it came out of the plant.
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Postby Labhuntr » Wed Mar 12, 2008 11:17 am

I had a 98 Z71 and the only problem I had with it was there must of benn a magnet in the body panels somewhwere, because I kept getting run into :rofl: I got in three accidents with that truck and not one of them was my fault!! Had to get rid of it sick of driving loaners from the body shop. But otherwise I loved the truck!!
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