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Cooling System Overhaul - Stumped and Frustrated

dhcomp said:
Interesting. I only went 3 wire cause i couldn't' get the check engine light off with the headers.
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Which code was it?

Never had a problem with unheated O2 way back in long tube headers, it just went open loop while idling, but that didn't trigger an O2 code...not sure why yours would unless there is another problem that the O2 is helping to hide, which would manifest itself ONLY under heavy load.

You see this thread? http://coloradok5.com/forums/showthread.php?t=315621

Exact same problem an O2 sensor can't "fix" under heavy load. However an O2 sensor can hide the problem under part throttle/light throttle cruise.
 
dyeager535 said:
Which code was it?

Never had a problem with unheated O2 way back in long tube headers, it just went open loop while idling, but that didn't trigger an O2 code...not sure why yours would unless there is another problem that the O2 is helping to hide, which would manifest itself ONLY under heavy load.

You see this thread? http://coloradok5.com/forums/showthread.php?t=315621

Exact same problem an O2 sensor can't "fix" under heavy load. However an O2 sensor can hide the problem under part throttle/light throttle cruise.
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Hm. Wish i remembered. It was a while ago. I'll read back on my thread and see if i talked about it :doah:

Interesting idea. I guess i'll know after testing without the o2.
 
Won't make a difference without the O2. It isn't providing feedback (fuel delivery isn't being adjusted) when *you* are having the problem, you'd need to be able to see the O2 sensor readings real-time. Wideband is preferred, but a narrowband is good enough that if rich it will show rich. If lean it will show lean.

Is that making any sense, or should I break it down a bit more to understand what's going on under the two conditions (light throttle cruise and under heavy load)?
 
dyeager535 said:
Won't make a difference without the O2. It isn't providing feedback (fuel delivery isn't being adjusted) when *you* are having the problem, you'd need to be able to see the O2 sensor readings real-time. Wideband is preferred, but a narrowband is good enough that if rich it will show rich. If lean it will show lean.

Is that making any sense, or should I break it down a bit more to understand what's going on under the two conditions (light throttle cruise and under heavy load)?
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Its making sense, but i'm unsure how to proceed to test it.

What do we think my best bet is to get it to fuel properly under load?

Go back to the 1 wire o2?
 
Me and Dorian are talking about two situations. I'm saying unplug to test that the o2 isn't falsifying things. Dorian is saying that headers require fueling adjustments. Which is true but I would figure you corrected that with upped fuel pressure.
 
So my line of reasoning is such that with the o2 not sending reports back to the computer, the computer running at factory defaults, with upped fuel pressure should run a bit on the rich side. I still say it's a cheap fast and easy thing to rule out and test by just going for a drive with it unplugged.
 
No reason not to try the free and easy!

Agree with fuel pressure, might be able to fix a lean condition by adjusting it (depends on how much fuel is needed, and if the pump is capable of supplying more pressure). As the example given shows, adjusting fuel pressure alone can solve a problem in one area of engine operation, and cause problems elsewhere/at other times.
 
I know this sounds completely off the wall and I hesitated bringing it up, but I had an overheating issue last fall and it had me stumped as well. My temp gauge would go to 210* and then bounce up and down. I thought it had an air bubble but it never burped anything out. I had a new water pump, thermostat and radiator hoses, and it still did it. It should be noted that I'm not running an external trans cooler.

Anywhoo, I was doing my fluid checks one day and noticed my trans fluid was low and looking a bit dirty. I did a flush/filter change in October and so far it's never gotten hot and my temp gauge stays right at 210* no matter how hot it gets outside. Coincidence, I don't know. But maybe the old fluid got hot enough to transfer the heat to my radiator and it struggled to keep the coolant cool. :dunno:
 
snuffy74 said:
I know this sounds completely off the wall and I hesitated bringing it up, but I had an overheating issue last fall and it had me stumped as well. My temp gauge would go to 210* and then bounce up and down. I thought it had an air bubble but it never burped anything out. I had a new water pump, thermostat and radiator hoses, and it still did it. It should be noted that I'm not running an external trans cooler.

Anywhoo, I was doing my fluid checks one day and noticed my trans fluid was low and looking a bit dirty. I did a flush/filter change in October and so far it's never gotten hot and my temp gauge stays right at 210* no matter how hot it gets outside. Coincidence, I don't know. But maybe the old fluid got hot enough to transfer the heat to my radiator and it struggled to keep the coolant cool. :dunno:
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Thanks for the idea. Mine is full, and fairly recent, but i plan to change it out in the next couple months.
 
Ok.

Bumped fuel pressure to 15psi.

Idles REALLLY smooth.

Added Redline Water Wetter.

Changed oil.

Ready to head up to tahoe tomorrow. Heading up in the evening, so shouldn't be hot out.

I'll report back. Wish me luck.
 
dyeager535 said:
Here's luck! You need it with this problem. :(
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Thanks. I have every intention of playing with O2 sensor, but haven't had a chance to do so and be able to test drive it.

We shall see how it goes, and possible disconnect the O2 for a bit on the way home (unloaded) sunday.
 
Assuming your FPR is easily adjusted and fuel pressure easily watched, can always turn it back down if the problem disappears, see if it comes back.

I've not ever needed Water Wetter for it's (supposed, I'm ever skeptical) drop in coolant temp, but if the issue does disappear, would be nice to know what fixed it.
 
dyeager535 said:
Assuming your FPR is easily adjusted and fuel pressure easily watched, can always turn it back down if the problem disappears, see if it comes back.

I've not ever needed Water Wetter for it's (supposed, I'm ever skeptical) drop in coolant temp, but if the issue does disappear, would be nice to know what fixed it.
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Yah. Fuel pressure is easy enough to change when the motor is cold, but its sucks to do when its hot. THe fuel pressure gauge is in-line to the tbi, so its easy to see under the hood, but not visible while driving.

Definitely though about wanting to know what fixes the problem, if it improves.
Trying 2 things at once keeps me from knowing what helped, but at this point, i'm more anxious to fix it than to Know what fixed it. :haha:

We shall see.

Also curious to see what Fuel pressures vs. MPG changes i notice.
 
Well technically consumption has to go up (and MPG down), but that would only apply under heavy load, ECM should remove fuel as necessary during light throttle operations.

Might be ready with a paperclip and a code reference chart just in case you throw a CEL. Not likely, but if you dump too much fuel you might get one. Never a bad idea to have those two things around just in case anyway.
 
dyeager535 said:
Well technically consumption has to go up (and MPG down), but that would only apply under heavy load, ECM should remove fuel as necessary during light throttle operations.

Might be ready with a paperclip and a code reference chart just in case you throw a CEL. Not likely, but if you dump too much fuel you might get one. Never a bad idea to have those two things around just in case anyway.
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Yep. Just curious if I see a big difference in unloaded cruising at highway speeds.

My assesment was going to be in teh realm of "yep, it normally takes me more or less than 1/2 of a tank to get to.....". Not calculated values. If i burn an extra 1/4 tank, i'll take note, otherwise, it is what it is.

Last time i checked towing up to tahoe, i think i got 6mpg :eek1:

Will definitely have a paper clip around for the reason. I can always do a quick code search online. Love being able to do that on these trucks!
 
Well, manifold and 15 psi of fuel made it pull a little stronger

About 70 outside at the base, got to 3/4 temp gauge, which was higher than I wanted. That being said, that is really only 235. Should I worry? Have I made a fuss about nothing?

Any strong grade pull would hit 3/4 gauge, but didn't see higher.
 
Pulling a 3500 lb trailer through the mountains in my '90 Blazer I never saw temps exceed 210. 210 would be a long grade, then shortly after the summit it'd drop back down to 195 and stay there. This is a fairly high mile 350/700R-4, 35's and 3.42's towing in drive (~2000 rpm freeway)

235 would freak me out!
 
Agreed. No matter the circumstances (assuming I had enough coolant) I've never seen one of my trucks go over 210 on the gauge before it came back down when the t-stat opened.

I'd start messing with the O2 sensor.
 
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