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Discussion Starter · #1 ·
First time on here need opinion from others who know more about this vehicle. I have a 2006 trailblazer ext 4x4, 4.2 6 cylinder 220,000 miles. I noticed a burt oil smell a whole back so I pop the hood and look for any leaks. I see oil running down from what I assumed was the valve cover gaskets ( know a little but will admit nowhere near a mechanic . So I call my mechanic and tell him I'll pick up the gaskets and drop it off in a few days. Today he calls me back and says he isn't going to change them because I have severe blowby and it wouldn't do any good. I go pick up the trailblazer and bring it home, take off the oil cap while it's running. No smoke, no pressure coming out when I hold my hand over it. No ticking and runs smooth. Will admit it doesn't have the take off that my wife's 07 trailblazer does but can blowby cause this much oil? It has had a leak as of late fee drops under it right after I park. Did notice today that there was a drop here and there landing on the hot exhaust because you could see the smoke pop up and smell it burning more.
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2004 Trailblazer LS 4.20 L
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does it blow blue smoke at start up? how often do you add oil if at all? if you dont need to add much oil between changes and its not coughing out blue in the morning then you just need the gasket, grommets, spark plug tube seals, and yeah spark plugs will get that pep back in your step. mechanic probably pulled a spark plug and the well had some deep oil in it. thats common, burns up plugs too. its from the seals leaking, not blow by.

look at rock auto for cheaper parts. some people will try to tighten the valve cover bolts up but id be careful. use a torque wrench if possible but if they are real loose you can gently snug them. wont help the plugs out much though
 

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'05 Chevy TB EXT
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You've got those oil leaks because you have pressure in the crankcase.

Solve THAT and you might cure all your oil leaks.
 

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Discussion Starter · #5 ·
does it blow blue smoke at start up? how often do you add oil if at all? if you dont need to add much oil between changes and its not coughing out blue in the morning then you just need the gasket, grommets, spark plug tube seals, and yeah spark plugs will get that pep back in your step. mechanic probably pulled a spark plug and the well had some deep oil in it. thats common, burns up plugs too. its from the seals leaking, not blow by.

look at rock auto for cheaper parts. some people will try to tighten the valve cover bolts up but id be careful. use a torque wrench if possible but if they are real loose you can gently snug them. wont help the plugs out much though
I put about half a quart or so every 3000 miles. No smoke at all other than when oil drops down on the exhaust. I took it to another mechanic and he confirmed massive valve cover leak ( which is what I originally thought ) I think the first mechanic just didn't want to bother with it. Thanks .
 

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2004 chevy trailblazer_lt
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Discussion Starter · #8 ·
just ignore me ... good choice.... bye
They looking into that too.
OK, I'll tell him.

You need to clean your PCV system! See this for more information and how to clean it.

Thanks.
OK, I'll tell him.

You need to clean your PCV system! See this for more information and how to clean it.

Thanks for the info. Love this vehicle and want it to last as long as possible. I am still learning when it comes to working on them though.
 

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2004 Trailblazer LS 4.20 L
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They looking into that too.

Thanks.

Thanks for the info. Love this vehicle and want it to last as long as possible. I am still learning when it comes to working on them though.
the PCV can cause increased crank case oil pressure, which gets relieved through the spark plug tube seals and valve cover gasket. whichever gives first. either is better than the head gasket. any time you've got missing oil it could be something less than great. pint every three thousand is enough to start investigate for sure. i like to change my 4.2 L6s at three when im running dinosaur oil and getting it done somewhere.

point is you may as well have that PCV changed on while they in there. should have almost no oil usage and minimal leakage afterwards. as long as they are competent or experienced with the atlas motors. sounds like wrench #1 just didn't know what they were looking at.
 

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'05 Chevy TB EXT
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the PCV can cause increased crank case oil pressure, which gets relieved through the spark plug tube seals and valve cover gasket. whichever gives first. either is better than the head gasket. any time you've got missing oil it could be something less than great. pint every three thousand is enough to start investigate for sure. i like to change my 4.2 L6s at three when im running dinosaur oil and getting it done somewhere.

point is you may as well have that PCV changed on while they in there. should have almost no oil usage and minimal leakage afterwards. as long as they are competent or experienced with the atlas motors. sounds like wrench #1 just didn't know what they were looking at.
Can you provide a part number for the PC Valve you say you can change?

We're talkin' a 4.2 here ...... okay?
 

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2008 Trailblazer 4.2LS
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You've got those oil leaks because you have pressure in the crankcase.

Solve THAT and you might cure all your oil leaks.
I too have similar seepage, changed PCV hose on driver side (GM #12575660 ) after cleaning with carburetor cleaners, Mechanic could push compressed air from driver side vent, still have high oil consumption.

Last week fixed vacuum leak on break booster.
 

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'05 Chevy TB EXT
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I don't get the corollary ... a vacuum leak from the booster should have zero deleterious effect on oil consumption ... just the opposite, really.

It WILL diminish the efficacy of the CV - side of the PCV system ... then you make chocolate mayonnaise.
 

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2004 Trailblazer LS 4.20 L
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I too have similar seepage, changed PCV hose on driver side (GM #12575660 ) after cleaning with carburetor cleaners, Mechanic could push compressed air from driver side vent, still have high oil consumption.

Last week fixed vacuum leak on break booster.
you can try to look in the spark plug wells and see if there is oil in them or you may see oil on the sides of the block. those things indicate a valve cover gasket mating issue. oil dripping from the drain plug may indicate a stripped pan or plug or leaky oil pan gasket. oil on the filter points to a poor seal on the filter. blue smoke at cold start is a sign of weak rings on the pistons.
 

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2008 Trailblazer 4.2LS
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you can try to look in the spark plug wells and see if there is oil in them or you may see oil on the sides of the block. those things indicate a valve cover gasket mating issue. oil dripping from the drain plug may indicate a stripped pan or plug or leaky oil pan gasket. oil on the filter points to a poor seal on the filter. blue smoke at cold start is a sign of weak rings on the pistons.
Thanks for the suggestion, will check with the mechanic on spark plug leakages.

In my country (Saudi Arabia) mechanics doesn't want to spend time on high mileage vehicles. The vehicle is giving good mileage 22MPG Highway and 14-15MPG City and their advise to add 1-2 ltr oil each month rather fix engine issue as spare parts not readily available. They are ready to fix minor maintenances which keep the vehicle moving.

The forum helped lot in resolve outstanding issue on Thermostat, PCV , vacuum leaks.
 

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Discussion Starter · #16 ·
Well went and picked up the trailblazer. Mechanic said the gaskets where very hard and brittle. When I mentioned pcv clog he did mention this vehicle didn't have a pcv valve but a system. ( which thanks to you guys helping I knew ) but lost faith when I mentioned the vent hose on the side and he said it only has the one on the top.. He did say while the intake was off he cleaned everything up and cleaned all the hoses and where they connect. I drove it the 10 min drive home and popped the hood to check his work. I pulled the dip stick out and held my thumb over it and there was suction (something I saw on a video by Joe Vreeland ). I'm not sure how much it was supposed to have but it was enough I could tell. Thanks for all the advice I will be checking for the signs and clean out that pcv system at the first little red flag from now on.
 

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2002 chevy trailblazer_ls
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First time on here need opinion from others who know more about this vehicle. I have a 2006 trailblazer ext 4x4, 4.2 6 cylinder 220,000 miles. I noticed a burt oil smell a whole back so I pop the hood and look for any leaks. I see oil running down from what I assumed was the valve cover gaskets ( know a little but will admit nowhere near a mechanic . So I call my mechanic and tell him I'll pick up the gaskets and drop it off in a few days. Today he calls me back and says he isn't going to change them because I have severe blowby and it wouldn't do any good. I go pick up the trailblazer and bring it home, take off the oil cap while it's running. No smoke, no pressure coming out when I hold my hand over it. No ticking and runs smooth. Will admit it doesn't have the take off that my wife's 07 trailblazer does but can blowby cause this much oil? It has had a leak as of late fee drops under it right after I park. Did notice today that there was a drop here and there landing on the hot exhaust because you could see the smoke pop up and smell it burning more.
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You definitely need to replace those gaskets, replace your pcv valve, clean the throttle body, etc.
try this, it work for me but of course I cant guarantee anything, you will do it at your own risk: remove the oil dipstick, secure it in an area where it will not interfere with the engine, install a breather on the disptick opening, in my case it has worked great, I did the same to my audi q7 and to my ford edge, I sold my acadia, she had the same, never any issues.
good luck
 

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2008 chevy trailblazer_lt
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I can definitely say that when I last changed spark plugs, I saw major oil around a spark plug or 2 and was surprised I didn't have misfires for that reason. I plan to do the valve cover gaskets with spark plug seals and cleaning the PVC system soon, now that I gathered parts.

Rob in AZ
 
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