2008 Envoy -- the good/bad/ugly...

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Might be looking at a lower mileage (121k) 1 owner Envoy this weekend. 4.2.

Other than what I've looked up -- valve seats, water pump, my guess window actuators......any other issues?

At normal temp, oil pressure gauge is showing a bit over 40 psi (idle)

Thanks.
 
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The oil pressure gauge on these cars is worthless. But if it's been maintained it should be fine, the only thing I can tell you is if your water pump or fan clutch go wrong, just cut the fan shroud so it'll clear the upper radiator barb. The thermostat is a bit of a pain to change on these. The exhaust manifolds are a bit infamous for cracking. Expect to change the speakers because water likes to get in around the window seals like all gm truck platforms. All the normal older getting up there in miles 4L60E issues, also engine mounts. The valve cover gasket is a tremendous pain to replace you have to get the intake manifold off first, and the rear most bolt is an absolute pain to get to.
 
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The oil pressure gauge on these cars is worthless. But if it's been maintained it should be fine, the only thing I can tell you is if your water pump or fan clutch go wrong, just cut the fan shroud so it'll clear the upper radiator barb. The thermostat is a bit of a pain to change on these. The exhaust manifolds are a bit infamous for cracking. Expect to change the speakers because water likes to get in around the window seals like all gm truck platforms. All the normal older getting up there in miles 4L60E issues, also engine mounts. The valve cover gasket is a tremendous pain to replace you have to get the intake manifold off first, and the rear most bolt is an absolute pain to get to.
And other than that these things are bulletproof! LOLOL!

/s
 

AZjeff

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Is this the same platform as the old Trailblazer that has the tie rod going through the oil pan or some weird thing? Not sure it matters but it might complicate some repairs down there.

Yes it is.
oil pan 003.jpg
 

JTK

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I believe 2008 or so was the last year for the GMT360 chassis. I still see a lot of them cruising around the rust belt. Seem to have held up OK. I liked our 2005 the time we owned it. Even on the 4x4's all fluid maintenance was super easy, as well as spark plugs coils, etc.
 
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Ok, I'll play devil's advocate: despite my inherent hate for the GMT360's, I'd be lying if I said they aren't a reliable if not finnicky truck. The Atlas motor is basically bulletproof, it's everything that's bolted to them that causes issues. To name a few:

Electro-hydraulic fan clutch
Water pump
Alternator
Thermostat
Injectors
Coil packs
AC hoses
Radiator
4L60 trans
Window regulators

Etc, etc. Friend of mine currently owns a Trailblazer with well over 200k and it's been mostly reliable, but it's still running. Bottom line, I'd skip it.
 
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Ok, I'll play devil's advocate: despite my inherent hate for the GMT360's, I'd be lying if I said they aren't a reliable if not finnicky truck. The Atlas motor is basically bulletproof, it's everything that's bolted to them that causes issues. To name a few:

Electro-hydraulic fan clutch


Etc, etc. Friend of mine currently owns a Trailblazer with well over 200k and it's been mostly reliable, but it's still running. Bottom line, I'd skip it.
My 08 doesn't have an elctro-viscous clutch it has just a regular thermal clutch, I think they stopped using the elctroviscous after the 07 model year.
 

JTK

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My 08 doesn't have an elctro-viscous clutch it has just a regular thermal clutch, I think they stopped using the elctroviscous after the 07 model year.

I had forgotten about the E-viscous fans they used and didn't realize they finally phased them out.

Do they still have the air injection system with the electric blower under the vehicle, about under the driver's seat?

I never had any mechanical issues with our 2005, but we only owned a few years and from maybe 16K miles to ~50K.

I just remember the fit/finish and body panel quality being so bad. I had wind noise from both front doors. The dealer fix was to have the body shop bend the window frames in tighter. It worked. LOL.

I bought our white 2005 LS 4x4 as an ex-rental in 2005 w/ about 16K miles on it. I paid around $15K for it. Those were the days.
 
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I bought an '07 in '10 with 29k miles on it. Had the water pump, front hub and fuel sender replaced under warranty. The basic foundation of these trucks are very durable and of high quality (argue over the 4L60E but no worse than most transmissions). The engine is a masterpiece of simplicity and smoothness.

Things known to fail going into the 100k mile range:

Fan clutch
EVAP solenoid(s)
Fuel sending unit
Front hubs
Throttle body gets coated in goo and causes rough idle.
Ignition switch (I'm on my 4th one and keep one in the glovebox, seriously)
A failing ignition switch will cause all sorts of odd problems. No crank, missing air vent fan speeds, abs light, etc.
Motor mounts. They are fluid filled and when one busts you'll get a nasty vibration.
Dropping gas mileage for various and sometimes unknown reasons.
Potential oil usage.

At 149k it started drinking oil. 2,000 miles into an oil change it was 3 quarts low and spun a bearing. I ran PP 5W30 since 29k. No leaks, no smoke. Oil use is not common, but not rare either for the 4.2.

I replaced the engine and my daughter is driving the truck now. It drives like a new vehicle. Tight, quiet, smooth. Knock on wood!

She short trips it to school and it gets horrible mileage, probably in the 10 mpg range.

I've been casually looking for another, but will not buy a 4wd due to the oil pan/front axle thing. I'd hate to have dealt with that during the engine swap and the ones I'm seeing for sale don't have a lot of life left in them, at least not that I'd bet on.
 
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Bud_One

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Coworker had a 2004 Trailblazer that he just recently got rid of... 280k miles ,4.2 I-6 .
Mostly a repeat of what the previous have posted.
He had trans go out twice , multiple issues with fan clutch and thermostat.
I changed the plugs on it once . It was rode hard and hung up wet , it held up well to the abuse it was put through.
 

mjk1967

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Well, I will let you know what happens..... thanks for the heads up.
 
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I know mine does, one wither it threw a code because condensation got down into it and froze.
This was the single DUMBEST design choice, short of the GMT800 trucks with their ABS modules mounted about the same place. Whatever engineer came up with the idea to mount the AIR pump at the lowest point of the system should be taken out to the Nevada desert and shot, Casino style. Basic physics would have easily exposed this design flaw. Cold, moisture rich air from the lowest point in the circuit meeting hot engine compartment temps was a recipe for disaster. The output of from the AIR pump became a literal drain spout, with the pump being the "sump". How this got by engineering is beyond me, other than the fact that we're talking about bankruptcy-era GM.
 
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If prices are similar in your area, just get a tahoe/yukon/escalade GMT 800 and call it a day. I wouldn’t not get a 360 platform but it would have to be a great deal.
 
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Vehicle isn't great, but Atlas engine is a great candidate for a swap into some old vehicle, cruiser or muscle. Restomod style. Allegedly Atlas inline six responds extremely well to boost, which gave it names like "GM Barra" or "GM 2JZ" in the tuning community.
 
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