Dad is looking at a few Yukon's of the early '00s to keep at a second residence, apparently GM did an engine switch from the 5.7 to the 5.3 around that time. What's the better choice regarding longevity and reliability between these two? Any info? I think these are all XL models that he's looking what, but I don't know what that means, or if it means anything.

Thanks.

[This message has been edited by Rainman (edited 07-31-2011).]

XL is extended length.
I work in the used auto parts business and can tell you we sell a lot more replacement 5.7 engines than 5.3s. GM made a lot of engineering changes for the with the LS series of engines.
I don't or won't own either, but that is my experience with them.

Gene

They both had intake gasket problems. The 5.7 had injector issues. The 5.3 likes to break the exhaust manifold bolts and would cause exhaust leaks...but then again, the 5.7 did that too. Hmm, kind of a toss up? The 5.3 is the newer design, but it was the first or second year they used it. It was one of the last years you could get the 5.7 (350 small block chevy), so it stands to reason that most of the bugs were worked out, but they weren't.

In all honesty, I would call it a toss up between the two as far as reliability and longevity. The 5.3 should get a little better mileage and have more power.

Thanks for the info so far! I'm passing it along.

I've got a 5.3 in my '05 Silverado.
It's all newer technology vs old. I'm still learning about it, but I'm impressed. 325 CI and ~290 HP.
IMHO, it's far superior to the old 5.7 / 350. (Keep in mind that there is a also a newer 5.7. aka the LS1. I don't believe it was ever installed in trucks, however.)

The first thing I ever had to do to mine was replace the knock sensors. They're mounted in wells, between the cylinder banks. If the seals get compromised (one of mine got mouse chewed ) It can allow water to get down into the wells and short out the knock sensor. (Only one was shorted, but I replaced them both while I had the intake off.)

Regarding the intake... It's a one piece plastic design, that doesn't serve as a valley cover. You can remove it without opening the cooling system or otherwise going into the engine. No coolant goes through the intake manifold, unlike the 350.
The gaskets are molded plastic with rubber (silicone?) inserts. In retrospect, I probably could have reused them, but I never have before, so I didn't even think about it before I bought the new ones.
In contrast, the 350s use typical gaskets that require sealer around the coolant ports, and etc. Used to be a much nastier job.

As with anything, the newer the year model, the more bugs that have been worked out of the new design.

Edit - For reference... I've had several "old" small blocks. A couple of 262s (75 and 76 model year only. They were dogs) and a couple of built up 350s, and a 305.
I've also had a couple of 4.3s, that were essentially 3/4 of a 350. They were okay, but the LS engine, including the 5.3, is far better.
It moves my crew cab Silverado really nicely, for how big it is. Got 16 MPG with the bad knock sensor, and my lead foot.

[This message has been edited by Raydar (edited 07-31-2011).]

Short answer:
5.7 - old school small block chevy 350. Throttle body FI, IIRC.
5.3 - smaller version of the LS1 engine - Gen III.

The 5.3 will be more powerful and get better mileage.

I have 176,xxx miles on my 05 Silverado with the 5.3 and it runs like new. Previous owner kept all service records and the motor has not had any major work done to it. I know it gets better gas mileage than my wife's Grand Cherokee and that is a smaller V8.

All in all, 5.3 = a darned good motor.

I would take the 5.3L over the 5.7L any day. Very nice engine series. As said above, they love to break exhaust manifold bolts. My 6.0L was a dream but I had to finally remove all of the exhaust manifold bolts and switch them to quality studs. It ate them for breakfast.

Have a 99 Silverado with over 250,000 on the original 5.3. Very, very good engine. It's the 99-03 trucks you have to look out for. They rust out like CRAZY!!

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1986 SE 350 V8

quote Originally posted by tesmith66: Have a 99 Silverado with over 250,000 on the original 5.3. Very, very good engine. It's the 99-03 trucks you have to look out for. They rust out like CRAZY!!

Include the 04's in that statement. I have a door rusting out on my 04 Sierra.
I had 3 injectors fail simultaneously but other than that the engine has been good.

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86 GT
87 coupe restoration project.

quote Originally posted by Raydar: Regarding the intake... It's a one piece plastic design, that doesn't serve as a valley cover. You can remove it without opening the cooling system or otherwise going into the engine. No coolant goes through the intake manifold, unlike the 350. The gaskets are molded plastic with rubber (silicone?) inserts. In retrospect, I probably could have reused them, but I never have before, so I didn't even think about it before I bought the new ones. In contrast, the 350s use typical gaskets that require sealer around the coolant ports, and etc. Used to be a much nastier job.

This is true, but the intake gaskets still leak engine vacuum. That is the failure mode of them. Causing rough idle, lean conditions and check engine light. I have replaced a few cylinder heads on these engines too (4.8 or 5.3 can't remember which) due to cracks in the head causing coolant consumption and intermix of coolant in the oil.

Still, both good engines in my mind.

Oh, I can't believe I forgot to mention the piston slap on the 4.8, 5.3 and 6.0. They get pretty loud in cold weather, but quiet down after a minute or two of running.

...and cold start knock. The "piston slap" in mine turned out to be a hard rubber restrictor in one of the heater core lines, right at the core. Took that out when replacing a rotted out quick-donnect fitting (thanks, death-cool) and the "slap" sound went away completely.

Whatever you get, be sure and remove the red anti-freeze. It is the source of all of the intake gasket problems. Replace it with good old green and forget about it. As I said above, mine has over 250,000 on the original engine (that includes gaskets). I replaced the red with green after the aforementioned fitting rotted away at around 50,000 miles. Was too late to save the heater core, though. It let go a few months later.

Awesome info. Thanks for all of the help. I think he'll be going the 5.3 route unless a 5.7 comes along for a steal, but he's already looking at a 5.3 equipped model, will probably go that route.