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Discussion Starter #1
2006, 3.5L, 4x4, Z-71.

Ok...so for the past 3 months I have been trying to decide the future of my Colorado. I bought it brand new in 2005. 15 years (and two children later) it's time to make a change. Truck has almost 175,000 miles on it. Garage kept. Here are my concerns:

1. New Colorado that I want is going to be around $45,000. That's a steep monthly payment. Dealership won't give me much over $3,000 for mine.

2. Reading over the forums and seeing the issues with the new models, wondering if I want to go through that headache again with GM.

3. I like a challenge.....

So I was wondering if anyone has done a complete overhaul on this truck? I know I will need:
Complete engine rebuild, exhaust, many aesthetic items...but what about transmission? Differential? Main computer? I've done quite a bit myself as routine maintenance (wheel bearings, plugs, coils,.etc). What am I looking at as far as cost? If I want a complete overhaul from bumper to bumper of the main components of this truck? Are we thinking $10,000? $15,000? I really would like to keep the engine, just rebuild it. I want some performance upgrades and modifications,.i.e. better intake and exhaust, correct the pcv issue, correct the valve issues....any thoughts? Or have I simply went full crazy?
 

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Discussion Starter #3
Yeah, looked into that.. I am really looking for more of what components have I missed? I know engine rebuild, exhaust system, not sure about transmission or differential, fuel system? All this can add up quick and before you know it you've dropped $20,000.
 

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If it ain’t broke don’t fix it. Drive it until it pukes then rebuild.

You’ll spend a ton of cash going through every component.
 

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Yeah WV, she's about to puke....I guess I failed to mention the important part. She's drinking about a quart to 1 1/2 quarts of oil every two weeks. I've been through her all the way, and with that oil consumption, I know I've got problems all the way to the exhaust. Hence the reason for either upgrade or rebuild.
 

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I don't know if this helps, but I purchased my '04 Colorado when it had 175,000 miles on it, and now it has just over 225,000 miles on it. I've replaced the plugs, both front hubs, changed all the fluids in front and rear differentials and transfer case, changed transmission fluid and installed a bluetooth stereo to meet our state's "hands-free" cell phone laws. That's a really cool thing by the way, to tell your stereo to call or text someone and have it respond and do that for you. Just a little side chuckle. My Father is in my phone contacts as "Daddy". The first time I told my stereo to "Call Daddy", the female voice responded: "Who's your Daddy?" I laughed so hard I had to pull my truck off the road and just sit there laughing! I've never been "dissed" by a computerized female voice before!
Back to business. I've owned 3 Chevrolet trucks in my life. A '69 C-10 with an inline 6 and 3 on the tree, an '87 Silverado and now my '04 Colorado. I put over 300,000 miles on the first 2, and plan to get that out of the Colorado too. The '69 truck had a few clutches replaced and I had to replace a couple of internal gears in the manual transmission. That truck was made when you could rebuilt the whole thing with pliers and a screwdriver though. When second gear went out, a buddy of mine gave me an old 3 speed manual transmission that he had laying around and I used it for spare parts. I'd just take the cover plate off of both of them and look for something broken in mine and take that part out of the other transmission and put it in mine. It was mostly a "user error" though. I loved to make it "bark" the tires when I slammed it into second gear! The '87 had a rough life beginning in about 2003 when I started driving a company car, and all 3 of my sons learned to drive on that truck and each of them had "limited ownership" of it for a few years. The deal was, it was their truck until the next one turned 16. Gradually, I noticed different colored body panels added to it. It was red and eventually had a black door and hood, then a white bed. They always repaired what they damaged, and paid for their own insurance, tickets and repairs. Eventually, my oldest son borrowed it from my youngest son to move home from college and he flipped it over twice going too fast on a winding country road. It had 312,000 miles on it. During its life, it had a transmission rebuild, a rear end rebuild, one son replaced carpet and installed bucket seats because the interior had gotten pretty grungy. It pulled several different boats and various types of trailers during its lifetime, and I honestly can't think of a single time that it actually stranded me anywhere! The rear end and transmission issues were gradually worsening issues that gave plenty of warning. It was a great truck. 5.7 V-8, automatic extended cab.
My Colorado has recently had the catalytic converter cut out, but it will probably be replaced soon. It needs brakes soon and rear axle bearings and I have a cracked exhaust manifold. I figure I can purchase all of those parts and install them myself for somewhere between 2 - 3 new truck payments. That's a no-brainer decision for me. It runs great, always starts and goes, it's gets a workout in my remodeling/flipping houses business, but it gets the job done. I pull trailers loaded with lumber and it never complains. If I had a catastrophic engine malfunction, I honestly believe I would replace the motor, or if finances were favorable at the time, I'd probably do a V-8 transplant. That's just me. I never buy new vehicles. I buy "slightly used" for about half the cost of new. This Colorado was an "emergency purchase" that I had not planned for, so I bought it for the amount of money I had in my pocket at the time when my car died. My intent was to drive it while I saved up for a newer truck. That was 3 years ago, and I plan to keep this thing forever.
 

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Discussion Starter #7
Good info oldguy. The only reason I wanted to keep the engine was it is definitely a good one to upgrade for horsepower. I dont have much loss in power, I feel the oil consumption is related to the notorious PCV drains. I may be able to get by with a valve job and exhaust replacement. While im in there correct the PCV issue. I've heard horror stories about the timing chain, so I am a bit hesitant to tackle it without help, and if I'm not mistaken you have to "brace" it to keep it from jumping on you.

I live in SC so my exhaust can be modified without government oversight....
 

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Yeah WV, she's about to puke....I guess I failed to mention the important part. She's drinking about a quart to 1 1/2 quarts of oil every two weeks. I've been through her all the way, and with that oil consumption, I know I've got problems all the way to the exhaust. Hence the reason for either upgrade or rebuild.
Out of curiosity, have you had the engine leak-down and compression tested? If you're losing that much oil, changes are your valve seals are definitely bad, and you may need new piston rings. A valve job on your current head shouldn't cost more than $500. These engines are generally very reliable, once you have a couple of issues taken care of. I've got 190k on my 04, with bad valve guides and a mild misfire, and it still runs great. It's got some other issues stemming from heavy off-road use (which I need to have diagnosed - my code scanner won't read abs codes), but is otherwise good to go.
 

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Reaver, yeah several weeks ago, I have a friend who is a GM mechanic do the compression test, he said I definitely need a valve job for sure. Which is my main focus, but while in there fix the PCV issue.
Main focus on this thread is are there any main components I need to be looking for? Let's say I do valves, head, exhaust, intake...that all can be done for under $5,000. Truck has been well kept, mostly farm use, never taken to the mud hole. Maybe I can away with correcting this issue and it be reasonable.
 

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Honestly, the only MAJOR issue I've ever really heard from these trucks revolve around the valve seals and guides, so I would focus on that, and then just address other issues as they arise.
 

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Alright...that's kinda what I was looking for. I've honestly been lucky with mine compared to others. The valve job and the exhaust replacement was already in the plans. I'm a bit nervous about tackling the valve job myself, I am going to get my buddy who does this for a living to help.
It's a great truck, pulls good, and I've had no issues untill the oil consumption, I wish I had paid more attention to what others were saying about the PCV system early on....but really...170,000 miles is pretty good to me.
I appreciate your replies...can't seem to see myself trading her in on a new one.
 

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Honestly, yeah, I'm with you there. With all the issues I've heard of with the new ones, trading it in doesn't make much sense, in my eyes. My Xterra suits my off road needs better, but the Colorado is a solid little truck, and I will be keeping mine for a while. Thanks for bringing up the PCV thing. I need to do some research into that on my truck as well.
 

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Yeah...there are some great discussions on here about the PCV and correction. It's about a 2.5 mm hole and it gets stopped up. Problem is that I haven't seen where anyone was successful at unstopping it without tearing it down. Not to say that it hasn't been done. But most people were able to clean it with a process using seafoam and allowing the vacuum to draw it in. I thought about trying it just because I have nothing to lose... but you know as well as I do...I got valve issues.
 

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The first thing I'd do is take the breather resonator off that sits on tip of the valve cover. When you take it off there's a hose on the back of the valve cover that will probably stay with the part you remove. Check out that little elbow hose and make sure it's not deteriorated from being soaked with oil. If it's broken, split or crumbles when you try to handle it - that just might be your problem! I found mine to be in really bad shape and it just fell to pieces when I tried to see if it was clogged. If it's in bad shape, my local Advance Auto Parts stocks a Dorman part, and they call it an emissions hose, if it's bad, it will cause excessive oil consumption. Here's the link:
 

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Also, if you're looking for a little performance boost, take the cylinder head to a good machine shop and have them port and polish it. That opens up the intake and exhaust so it will breathe better. Then contact supermodulation and get a ported throttle body. Then get some free flow exhaust components and you'll notice quite a bit of increase in throttle response and performance. You'll be fixing what's wrong and needs attention, and with a few more bucks replacing the worn parts with better-than-new parts, you'll end up with something that's better than it was when it was new. None of these modifications will really reduce the life expectancy of the truck, but will make it a little more fun to drive. And if you want to delete the catalytic converter, there's a neat trick for "tricking" the PCM where you won't get a check engine light. I did it to my truck about a month ago, and no light on the dashboard! Here's a link to that little trick (1/2" drill bit is the perfect size):
 

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That's what I am talking about! I appreciate the info. When I first began seeing the issue with the "spark knock" and oil consumption, I began looking for the PCV unit. That's when I discovered the crankcase ventilation hose you spoke of in your first post. Its crammed in there so tight, It looked pinched. I bought a new one off of rock Auto. Didn't see any changes (by the way, it did have oil in it, as well as the box had the milky oil in it). So I bought another off of GM parts giant...and same result. But that led me down the road to learning about the drain holes.

I plan on doing exactly the changes you pointed out. We have a great machine shop here in town that's tied in with a NAPA auto parts and they are good. Thanks so much for the advice.
 

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I would recommend doing a “compression check”. Dry and wet. I think you will find that your valve guides are worn. That is relative low mileage for the 4 or 5 cyl. engine. Like Old Guy said, “he has over 225,000 miles on his 4 cylinder engine. If you have any questions, text me at hhrumph. Good luck.
 

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I would recommend doing a “compression check”. Dry and wet. I think you will find that your valve guides are worn. That is relative low mileage for the 4 or 5 cyl. engine. Like Old Guy said, “he has over 225,000 miles on his 4 cylinder engine. If you have any questions, text me at hhrumph. Good luck.
Hhrumph,
I appreciate your reply. Yeah, as I stated earlier in this thread, I have a good friend who is a GM certified mechanic that did the compression test for me. He said it came back ok, but with the known problems for this vehicle, it would be wise to do a valve job. He also recommended an oil additive and fuel additive to address both the knocking and oil consumption. These both are strictly sold by GM. I have to say, I am a skeptic of any type of additive, but since he gave me the friends price I figured "why not?". I am not going to lie, the fist tank of gas with the fuel additive really blew my mind. Not only has the knocking completely stopped, but I have more power. I immediately changed my oil and added the oil additive....in two weeks my oil consumption has.changed significantly. At the moment, I am saving money for the rebuild and plan on valves, intake, exhaust, and maybe timing chain if I get brave enough.
 

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If it makes you feel better, mine has been experiencing similar symptoms for a looong time- probably 50-75k+. Mine is retired to lawn care tow rig/plow truck, but after snow season I'm replacing the engine and transmission with lower mile units after plow season.

What GM additive did they put in? I tried the seafoam, cleaning the port with a drill bit, BG engine flush, and bypassing the PCV port, and I still consume oil. PCV port bypass stopped the blue smoke startup after being on interstate.

Over 400k on the original gangsta 3.5- never been opened up. Odometer below is last Friday's storm.
340198
 
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