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06 I-350 (Z71 4x4 3.5L) K&N intake, both cats deleted, 152k

I've had considerable oil consumption for some time now (5-6 qts between oil changes) which I had chalked up to blow by and due to lack of funding, have not gotten past the "I'll fix it when I get my tax return" stage. The engine block is clean and the coolant was replaced in December along with a new water pump (coolant looks as clean as the day I put it in).

About a month ago, it developed a rough idle and a P171 code that comes and goes. I replaced the upstream O2 sensor and 50 miles later, the same code came back. I then got new spark plugs, seafoam, and a new exhaust cam actuator. The actuator was in hopes it would return some of the power lost around 25,000 miles. Unfortunately, the only result was after revving the engine to 2000 rpm, upon letting off the pedal, the rpm would drop low, then high, then low again before settling at the normal level. This for me was the "uh oh", and the "grab a beer" stage. I figured I'd clean the throttle body and run the seafoam through it before installing the new plugs and then see how it runs before worrying about the new erratic rpm situation.

After cleaning the throttle body I figured, why not clean the intake tube too, before the seafoam treatment. Upon doing this, I discovered a thick "milkshake" coating in the valve cover vent tube. Now I'm starting to pull my hair out. I checked the dipstick and the oil was 1/8in from the bottom, way below the cross hatch area, and milky with a rusty colored streak through it. Coolant resovoir was down 3" and the radiator was down almost 2" but the coolant looks new. Time for another beer!

I cleaned everything out, ran the seafoam through, topped up the oil level, and voila, rough idle and erratic rpm are gone! Had I not found the milky oil, I'd be jumping for joy.

I've been dwelling on the head gasket job and the possibility of a cracked head for a few nights and endless hours searching the boards, and am now thinking it may not be what it seems. I've read about the condensation issues with our motors and the valve cover vent baffle clog causing oil to get sucked through the intake and am wondering if these would be more likely. The oil on the dipstick looks clean after 75 miles and the oil cap looks good but the vent tube is full of milky oil again. Today I crawled under the truck and noticed an orange streak coming from the water pump area and I'm assuming the little bit of smoke in the exhaust is from the vent tube issue. I'd like to figure this out before putting the new spark plugs in.

I can't afford to spend more than absolutely necessary so any opinions, past experience, random theories, would be most appreciated.


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I am far FAR from a pro on this, but here are a few things I picked out of your write up. Milky oil is usually caused by water. Not many places that these two get close enough to tango except up around the cylinders. If there is a crack in your block/head it may be allowing the coolant to mix over. Your coolant would remain looking clean since the exhaust stroke would be blowing the nastiness out of the tailpipe. The smoke your seeing may actually be steam from the water introduced to the cylinder being boiled off.

Again, I am no pro. My specialty is jets and turbine engines. But we all sit around and have BS sessions when we run into an issue and every once in a while, after sifting through the garbage, some one will say a word that triggers a thought that ultimately answers the question!
 

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Wow. I got nothing to offer, but I'm in for info when the smart guys here check in.
 

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Discussion Starter #4
Today I'll pick up a radiator pressure tester and wipe off the coolant from the front of the block and go from there. It was starting to rain the other day and I don't have a garage, otherwise I would have done it then. I'll also do a compression test if I have time and post the results. I know for sure I'm burning oil because of the vent hose since a day after thoroughly cleaning it out, the milky oil is again going inside the intake tube fitting.

Does anyone know if the the valve seat issue can be remedied by a head mill and valve lapping in case I do have to take off the head and assuming I don't find any cracks?


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