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Author Topic: Does this gunk mean I have an internal engine coolant leak?  (Read 130 times)
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Tronman
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« on: February 01, 2018, 05:58:26 PM »

So while I was working on the EGR valve, I happened to check the oil.  It looks a little dirty, but still translucent and honey colored on the stick like always.  But when I pulled the PCV valve, there was this yellow gunk under it.  I stuck a finger into the oil cap hole and this came out.

I've seen it have some condensation under the oil cap in the winter, but never thick gunk like this.  There are no visible external coolant leaks such as the LIM, for which these engines are known.  But before the weeping and head gasket R and R out in the rain begins, I thought I'd run this by the ole' Aztek hive mind.

This engine has been well maintained and it has never overheated, and I've never had to take any of its lids off-however it does have 227K miles on it.
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wstefan20
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« Reply #1 on: February 04, 2018, 07:02:40 PM »

Well that is strange.... usually coolant mixed with oil is milky and chocolate colored. This definitely isn't normal. Have you been losing coolant recently? If so, I'd rent a pressure tester at oriley's before condemning the engine. Any other info that might be pertinent?
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Tronman
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« Reply #2 on: February 10, 2018, 12:20:13 AM »

Can't think of anything.  The vehicle has used slightly more coolant lately, but it's had a slow radiator leak for some time.  Due to a lean running condition which I believe to be the cause of a random misfire which causes the engine to go into OLD (basically return to a sputtering idle) like clockwork at 41 percent calculated load..  I'm taking the top off the engine for LIM gaskets anyway.

Since LIM is about eighty percent of the way to head gaskets, I'm gonna do 'em while I'm there.  Still hyped on my Aztek overall, I intend to keep it for another 200k miles..  plus the bottom end is solid, it's never used a quart of oil in total for the whole time I've owned it.
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Tronman
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« Reply #3 on: February 11, 2018, 01:26:44 AM »

Yep, there's an internal coolant leak..

But I'm not entirely sure it's the head gaskets..  As you can see in the pic, I caught it pretty quick as the gunk hadn't even spread all the way from the rear of the engine to the front..  (left side of the car to the right..)
« Last Edit: February 11, 2018, 01:28:02 AM by Tronman » Logged
Tronman
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« Reply #4 on: February 11, 2018, 01:31:58 AM »

The other thing I noticed is that when I removed the LIM, the rearmost bolt to the right was barely tight at all, like almost finger loose.  The others were all regular torque and required some effort to loosen.  Are the LIM bolts torque to yield?  Do I need to replace them?

This is all removing factory parts, no one has ever taken this engine apart before.
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Tronman
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« Reply #5 on: February 12, 2018, 04:59:12 PM »

Well I got the heads off..  it wasn't the gaskets.  They looked great.  No evidence of leakage, it was all the LIM :-/

So I went a lot farther than I had to..  but I'll still take the heads in and have them cleaned, checked, and the new seals installed.  I suspect they're fine.

On the plus side, I found some broken exhaust manifold studs and some leakage, and boy will those bolts be easy to extract now versus on the engine..  Also fixing those leaks will reduce the incidence of air (oxygen) being sucked into the exhaust stream, fooling the computer into thinking the engine is leaner than it is.

Also on the plus side, the cylinders look fantastic!  You can still see some factory hone marks, there is no ring groove at all in any hole!  No wonder it's never used any oil.  So I feel pretty good about putting a freshened set of heads on this seasoned bottom end.  Also, I found the cold engine clickety clatter..  when I turn the crank back and forth, you can hear the timing chain go click click.  However it's only two degrees or so of engine rotation, still tight.  Wondering if I should bother replacing it now while it's all torn down..?  It has made the exact same noise when cold since the day I brought it home, BTW.
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wstefan20
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« Reply #6 on: February 13, 2018, 08:25:53 PM »

Nice work! I don't think the lower intake bolts are tty, but I always use thread sealant on them (service manual says to at least for the 3100 engines).

Personally, I'd replace the timing set since they are relatively cheap, and you'll never have a better time to do it!

Be REALLY careful on the torque sequence and tightening when you replace the heads. I personally recommend having the machine shop resurface both the block and head, but in a pinch, use acetone and a plastic razor blade to get the surfaces clean. Don't use a metal scraper (ask me how I know).
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Tronman
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« Reply #7 on: Yesterday at 09:50:22 PM »

Good call on the thread sealant!  Back in the day, we used to use the white liquid teflon stuff on SB Chevy V8s for the bolts that went into coolant passages.  Will that be adequate?

The heads are in the machine shop now, I'll talk to Wes (NAPA North Bend, WA machinist w/30+ years experience) tomorrow and see how it's going.  I'm considering having a little port work done if it's not terribly expensive..  hey, while the heads are in hand, right?  I'll take 8hp if I can get it.

Will straight edge the block after careful cleaning.  But the engine never got hot, so I'm kinda doubtful that anything warped.  Also good advice about the plastic scraper, as I would have just cleaned it like every other cast iron deck I ever cleaned-and smoothed out with a fine flat file.

Slightly on a tangent..  I'm perusing the Fiero and F body forums and seeing people put rather a lot of work into the old '80s 2.8 version of this engine.  They're doing aftermarket cams that are good to 5000 RPM, and putting all this money into flogging those ole' small journal horses.  Seeing as how the far superior, lighter, 3400 version has modern day alloy heads with 50cfm better flow, roller rockers and will do 6200 RPM no sweat..   and can be had for a dollar fifty a pound at any wrecking yard in the country because GM made a gazillion of 'em and no one hops up minivans..  why would anyone not simply go this route instead?
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