Hi all,

newbie from NY here. l have an 04 Blazer LS, 4.3 4WD. 57K miles, bought new. Several issues over the last few weeks. l can build and tune a SBC just fine, but these newer computer run cars/trucks kill me, lol. l'd consider myself a glorified DIY'er...
While checking oil a few weeks ago, l noticed -stat housing leaking slightly. Coolant level was just below rad cap, added about a quart of water. Still had factory DexCool, which looked brown and nasty. Anyway, i just planned on replacing stat and gasket within a few days or whatever, merely to stop the leak. Had zero operational issues at the time. Few days later, SES light comes on, but still running fine. No worries, just running a little low on coolant, so l thought. Added water. Never checked code. Few days later l replaced stat, and flushed as much of the DexCool out that l could. added water, up to temp, filled reservoir to Full line.
played with water levels next few days. Started running hot, on a really hot day. damn near pinned the temp gauge, enough for check gauge light to come on. pulled over, and as soon as l shut it off, it puked a quart or two of coolant out the overflow.
in talking to a mech friend, he said to change stat again, could've been factory defective. did that, still got hot. Changed fan clutch. still gets hot. Changed water pump. was better for a week or so, but now it's escalated to not going above 35-40 mph, 2500 rpm's, and sounds like a bog when giving it throttle. PS, seems to run good when first started, after it warms up it starts acting up.
SEL light on, so took it to buddy, had P0101 Mas air flow, and another code for Catalytic converter, (don't remember #) MAF to see if any better. no. came back up with code for MAF, p0101. replaced MAF, no change at all. he says cat is clogged, to call dealer. ironically, my cat is still covered under the 8yr/80K Federal warranty, 'til Aug of '12, a few more weeks, lol. BUT, code for cat needs to be on sevice guy says.
now l can't get any code to come up, except for the MAF one. been driving it around neighborhood, probably about 10 miles now. Can smell the sulfur-like smell of a bad cat, temp is climbing to about 235, (the line between 210 and 260), and still running terribly. Going to try the test someone spoke about in another post about pulling an o2 sensor and seeing if it runs better.

does anyone have any other suggestions? l was thinking possible fuel delivery, with it not running right. l also just replaced spark plugs with new NGK's, btw.

thanks all for everyone's help. most pressing concern right now is if anyone has familiarity with the warranty, and them not covering it if no code.
thanks guys, Bill

 

I would do a fuel pressure and leakdown test first. If the cat is bad something destroyed it, usually that means it is running rich. Pulling an o2 sensor won't help anything, you can try to unplug the maf sensor to see if it helps.
As far as the over heating, it sounds like there is still air in the system.

 

By removing an up-stream (pre-cat) O2 sensor, you open up an exhaust leak that can allow excess pressure to vent restoring engine power lost from a restricted catalytic converter. So yes, pulling an O2 sensor can help in the sense that it is a valid test to tell you if the catalytic converter is restricted. If power is restored with the O2 sensor removed, then there is a very good possibility that the catalytic converter is plugged up.

The other symptoms fit with a plugged catalytic converter. I agree that something caused it to fail. Especially with that low of miles. Unless you were offroading and bounced it off of a rock, you likely have something amiss in the engine fuel system.

As far as the warranty side of things, they can run a back pressure test to confirm that the catalytic converter is restrictive with out the light being on. Really though, the code should still be present in the PCM. Clearing the codes does not delete them from memory.

Where in NY are you from Bill?

 

With the over heating issues I've seen that happen in my blazer almost word for word.
We evacuated the system & still couldn't get the air bubble out until we lifted the front PS & ran it with the rad cap off until it had reached normal operating temp. & then for a few mins at 1000rpm or so.

 

I misunderstood, I thought you were talking about pulling the downstream to trigger the ses for the cat lol.

 

Definately agree with air in the system causing the overheating. When I changed my coolant I refilled with the water neck and tstat off. I actually filled at tstat housing and it seemed to minimize air in system. I say cut cat and get money at recycling facility and get a catco universal cat from summit for $60-$80 minus the $30-$40 you get for the old cat. Total cost around $30-$40 dollars if u do yourself. Safe the hassle of the stealership.

 

Hi Guys,

thanks for the replies. l'm from Long Island, NY. l did pull the 02 sensor today, and although it was loud as heck, she ran completely normal. Temp never went above 210, full power through rpm range, and cruised at 70 just fine. l spoke to dealer today, and explained what l'd done, and she said she'll just write it up as an outside mechanic already diagnosed and addressed the MAF code, and they can just do a backpressure test to check cats, if the rattle itself isn't enough to satisfy her mechanic.
l also agree that something caused the cat to fail originally. my thinking is that the stat either stuck or was clogged with the dexcool junk, and overheated. Couple more times of overheating after changing stat, then water pump, and l think (hope) it caused the stuff in the cat to break up some, causing the blockage, then a couple more times of driving with the cat partially blocked just making it worse. She was running 100% normal beforehand, and even after first overheat, have had no other codes or issues, no smoke in exhaust, oil is crystal clean, nothing abnormal looking in coolant or tranny fluid, so l'm praying and hoping l don't have any sort of head gasket or intake gasket leakage. Also, never had heard the rattle from the cats before. lt's especially noticeable at idle in drive, ( i.e., stopped at a light) and with A/C on. it's certainly possible the rattle was there and i just never noticed, and am only noticing it now due to the present problems, but l guess l'll see next week when dealer starts work on it...
my true hope is that the initial overheat was actually caused by the cats themselves, and l simply misdiagnosed it. several times, lol...

thank you all for your time and replies. l'll follow up with developments. Bill

 

got the truck back from the stealership, and so far so good...

had to wait a few days for new pipe to be shipped from Michigan, but there's a new pipe and cat(s) from manifolds to muffler.

so far she has been running just fine, with zero issues. Tomorrow, l will put the front up on ramps and try to ensure l've gotten all the air out of the system, using the advice from above.

Other than that, dealer called to say some pinion seal was leaking on front differential or something, so l told them to change it. $89.

no explanantion as to the cause of cat failure, but the service person said the mechanic said it was broken up probably the worst he's ever seen, and it looked like simple heat failure, as opposed to being clogged with residue.

keeping my fingers crossed. have about 100-125 miles on it and not even a hiccup out of her yet.
thanks for all your help everyone.! Bill