Watch your UG for indication of closed or open loop fueling. If it does not go into closed loop, or stay in closed loop most of the time, then your mpg will stink. O2s performance determines when closed loop fueling takes place (closed loop = fuel mix constantly controlled by O2 and other sensors, open loop = ECU uses a wild guess)

 

So obviously I know my bank 1 rear sensor is fried .... however - from rewatching my video, i noticed the bank 1 front sensor hovers back and forth around 0.5 while the bank 2 jumps back and forth between 1.000 and 0.0000 ..... which of these is normal?

From where I am now on my head gasket job - valve covers off and all accessories that come before that, the bank 2 is where the leak is - the front of the engine where the head meets the block is COVERED with caked on sludgle right along where the gasket is while bank 1 is more or less clean. Perhaps both sensors are working fine and its the engine causing the wild readings on bank 2?

 

So - for the sake of everyone involved I am hoping to wrap up this thread!

Over the last few days I did a head gasket/valve job and changed both front O2 sensors. I moved the front O2 sensor that appeared to be working to the rear one that was dead and put 2 brand new ones in the front. The number 3 cylinder was bone clean while all the others were normal carbon black ... this makes me feel like this was the problem child. The results:

The good:
- No rough idle
- No hard starting at warm (yet)
- Seems to have more power and smoother (unless I am imagining this)
- The O2 readings in the ultraguage show that all sensors are responsive now and the 2 banks seem to be consistent
- the long term fuel trim has dropped from about 9% to 3% (negative)
- the engine load at idle has dropped from about 35% to mid 20s ... this seems consistent with what I read to be normal ...
- Overall I am happy I freshened the engine up and know what is there now.

The bad/unknown:
- The bubbles are still there ... but my mechanic friend took a look and says the amount of pressure is not consistent with an exhaust leak and hopefully this goes away over the next few days (his expectation)
- I am getting a spike in temp up to about 210 once after starting which dropped down within 20 secs ... from then on I was between 188 and 194 for all my driving
- My ultraguage says my instant MPG is between 700 and 4000 MPG ... and my fuel burn is almost nil ... don't know if this is a issue with the guage or my truck but abit weird
- Based on the above, I checked where the guage gets its data and apparently from the MAF sensor. I monitored this and it seems to be working but sometimes will drop to 0.09 g/s while I am on the highway or would otherwise expect high levels ... don't know if this is normal or due to a failing gauge ... otherwise it goes between 0.08/0.09 at idle and 0.70.

The interesting:
- After all my work we went for a ride and everything seemed good (other than the bubbles). Later I went for a 2nd ride and the temp spiked like crazy! I was ready to drive off a cliff and collect the life/car insurance.... But I think I figured it out ...

After the first drive, Happy with this, I wanted to make my engine look as pretty as I felt it was running and to match the shinny valve covers and heads back from the machine shop so I got some engine cleaner, taped/sealed up the electronics and made it shiny ... started up fine after so went for a drive. This is when the overheating happened. At first thought I got water in the sensor but this was REAL overheating (coolant overflowing) and not just a sensor. Abit later it came to me that I may have got oil on the fan belt and the water pump wasn't spinning ... drove back to where I left the truck on the side of the road, soaked the belt and pulleys with brake cleaner and cleaned the sensor with electronic cleaner for good measure ... no problems since.

Haven't been able to 100% confirm this is what caused the random overheat and I am not considering things fixed yet (since I also got another 20 sec overheat on another startup) but I think this probably makes sense...

Thanks to everyone that has helped me get to this point. I am hoping the emissions people end up being as happy with my truck as I am now! Will give it a week to wait for other problems to come up and if nothing does I will go for try #2.

 

And another update .... after a 2 hr drive with no movements between 188 and 195, I just started up the car and it climbed to 230 and didn't come back down like last time ....
Thermostat? Air in coolant despite my efforts to get it out?

$4k-5k into this thing and 4 full days of work for this .... I am done with this thing ....

 

Sounds like a stuck thermostat or a steam pocket. I'd put in a new one, 180F, with the little "jiggle" device (wire in a hole) at the 12:00 position. That lets air bubbles pass the stat and not build up a steam pocket. Remember, coiled part goes inside the block. If you think your stat is OK, but just does not have a jiggle device, you can drill a 1/8 inch hole in the flange, just put it at 12:00. But a stat is cheap, like $10.

 

That's what I thought made sense too but the thermostat is brand new LR brand thermostat and mounted as you indicated. About the steam pockey, don't know how to fix this - I did Spike method radiator bleed and had it running okay ...

 

A new hypothesis ....

I checked all coolant hoses for leaks and seals and since I didnt see any leaks on ground that we were okay but what about:

Water pump not sealed well to engine block at back (hoses okay) and therefore sicks air in when its operating .... air gets into system and explains coolant bubbles in system ....

These bubbles get into heater core and make the water running noise and also get into engine. When the engine sits these collect at the top of the intake near the thermostat and airlock the thermostat so that it cant tell that the engine has heated up and therefore doesn't start circulating.

I will check the bolts holding it on when I get home as it was one of the only things I did not remove as part of my head gasket job.

Would this explain things? Any sure ways to test? Any flaws to this theroy jump out? The one I can think of is that prior to trying the head gasket sealing stuff recommended and doing the HG job, I had gone months with no overheating (ever since replacing the rad). After trying the HG sealing compound, the truck ran fine and then all of a sudden overheated again ... I figured the thermostat was plugged, pulled it, and life had since been good ... Perhaps this sealing compound is still trapped in the water pump or heater and is plugging things up? The only thing is this would not explain why it would run for multiple hrs without issue ....

Edit: I thought about this more and realized that if my water pump was not mounted tightly I would see coolant leaking around it which I do not....

 

Unless anyone has any other ideas (I am fresh out) I am now down to two possibilities:
1) some type of leak in the heater core that I can't see that is letting air in
2) a slipped sleeve.

I feel absolutely sick to my stomach for not looking closely at the sleeves when I had the heads off ... didn't notice anything dramatic but after more reading apparently it doesn't slip much .... At this point, I am not willing to pay for a fix of the block if possible or replace the block as I am pretty much in this truck for as much as time and money as I can stomach so I really hope this is not the case.

Unless anyone has any other ideas, I am going to attach the heater hoses tonight and try to re-bleed. If I am still getting air bubbles I can't think of any other possibilities given I have no coolant leaking, just did a HG and ALOT of air is getting in somewhere (the tank will fill from half full and build up to the top then enough air will get released to let the level back down to the middle about every 65-70 seconds).

Given the #3 cylinder had no carbon on it while all the others did and I did not notice anything too obvious on the head gasket indicating it was leaking, I don't really know what else to think .... other than I am stupid for not looking at this more carefully.

If my worse fears are true, I am hoping I can recover at least half of what I have into this truck given it now has a rebuilt rad with <1000 miles, two O2 sensors with 100 miles, rebuilt heads, 5 new tires, and a very good condition body and interior.

 

stop leak may have clogged lower 1/3 of rad. pump bolts are various lengths careful u dont damage front cover

 

The rad seems to be working fine though ... after the overheating I went to the truck and the rad fluid was right up to the cap - I opened the cap and instantly a crazy amount of air came out the fluid dropped down to a normal level ... looks like the overheating was due to air in the system. After bleeding it ran fine and didn't overheat for 2-3 hrs. The problem is that air keeps getting in the system and given that I just did a head gasket, and see no visable leaks ...

Based on your reply, do you think the rad pump could be letting air in the system? I thought about this more and figured this would result in coolant leaks as well but since I cleaned the engine I am confident that the water pump is not leaking coolant.