Check Engine & Trans fluid questions

[jersey]

I have been getting a lot of check engine lights lately. A map sensor code showed up on and off a couple weeks ago. I added some fuel injector cleaner and that code went away and hasn't come back.

Now I got another check engine light and got two codes that read as p0128 and c0268

The c0268 reads as ABS sensor malfunction which is straight forward enough.

The other code though (p0128) reads as "Coolant temperature too low for thermostat regulating temperature"

Since when is running an engine too cool a problem?

The suggested repair is to change out the thermostat?

According to the gauge the temp is registering at the 1/4 mark, so i'm not sure what temp that is, but is there such a thing as too cool?

Outside temps here at the Jersey Shore have been fall like uppers 40's at night, mid 50's during the day.

So some advice please should I disregard the code or change out the thermostat?

With 137K miles on it, should I be changing the Trans Fluid or will doing so lead to problems? I ask, because the quick lube place I went to said they wouldn't change the fluid on any car with over 100K miles on it as a policy. That mechanic, if he even was one, said General Motors vehicles don't handle the change well, but wouldn't elaborate beyond that. So what do you think? Is there anything to that, or is it a bunch of mularchy?

Thanks

[HUMTECH]

Change the t-stat, gauge should be approx in the center at operating temp which is about 100 deg c. t-stat is stuck open not allowing engine to reach operating temp. As far as the trans oil change, some mechanics dont like to do them on high mileage vehicles if its never been done because in rare cases it starts to slip after the fluid change. I think your worse off not changing it myself. I have changed fluid at over 200k at the first change and never had problems.

[f5fstop]

I agree t-stat, especially on a vehicle with that many miles.

As for the trans....

Well, considering how hot the trans fluid in the H3 can run, I would guess at 107K the existing fluid is pretty well worn out. And with that many miles, I would not only recommend getting new fluid, I would recommend a backflush to get it all out. A drain only removed about one-third of the fluid, a backflush removes all the fluid.

JUST MAKE SURE, that it is done by a reputable place (suggest a dealer) who uses Dexron for the flush. Many of the aftermarket quick lube places uses a cleaner and the cleaner can cause more problems then not doing the flush. A reputable place will flush the trans with the recommended fluid for the trans (Dexron VI); thus inducing no foreign liquid into the trans.

Again, I suggest a dealer just because many use the Kent Moore trans backflush took which is highly rated.

[jersey]

Sad Update:

Did the Thermostat as recommended, however a few weeks later the plastic radiator cracked open. Had that replaced and did the tensioner too when it was pointed out as the source of the noise I was hearing in the front. In addition to this had the fuel injectors cleaned and the engine tuned. Left happy, but still didn't get the trans fluid changed. Next thing you know the car started with a shaking at speeds of about 40 MPH. Nothing serious at first, but made an appointment at the trans shop anyway. On the way there the trans popped. Case cracked. No surprise the shaking stopped as I rolled to the side of the road. Onstar towed it the rest of the way to the shop. Replaced trans, but shaking continued. It was determined the Universal Joint was slightly warped and that's likely what caused the shaking and probably what caused the trans case to crack in the first place. Had that replaced about 10 days ago and now the shaking is slowly coming back. I immediately brought it back, but my mechanic (in the biz for 20+ years) checked his work and says it's not the universal causing the problem this time and so he pulled the shaft and it seems to be running true too. So far he can't identify whats causing the shake. Just a little FYI he worked as a dealer mechanic for Hummer through 2009 and now operates his own shop.
If any one has any suggestions I can pass onto him, I'd appreciate it.

OOOP's: Forgot to mention that the rear leaf springs were changed with OEM springs (#25965051) in September 2012.

Question: What's the stock height for the rear of an H3 from 2006? Maybe the springs are defective in so some way and thats affecting the driveline somehow?

[iwillnc]

Well that sounds like quite a bit of suck, Maybe the torque converter wasn't reinstalled properly?

I'm sure it's internally balanced so wouldn't think the flex plate..


Does it idle fine?

I can't believe you cracked a 4l60e with a i5 though, that's rather impressive(unfortunately), I've blew a clutch packet with a 5.3 but it also weighed more.

EDIT: I guess the possibility exists it could be in the transfer case or maybe something in the diffs, highly unlikely but...

[iwillnc]

How was the original u-joint bent? maybe your rear diff has been pushed back creating a situation where the drive shaft is too short....

Well, then that would make no sense that it didn't effect the transfer case...

Just putting out ideas...

[jersey]

The U was likely bent when the rear spring passenger side popped in a NJ turnpike pothole. From there the steering wheel was turned nothing short of sideways. My wife had the H3 that day and drove it home like that for 60+ miles instead of calling for a tow truck. I took it to a local firestone and they threw in two new springs which they ordered from a local chevy dealership. That was September 2012. I'm starting to think the other driveline problems are related to that event too. Spring of 2012 I had the gear fluids replaced front and rear, is it possible that there's too little fluid? I'll ask my mechanic to check that too.

Edit: Come to think of it, I thought the idle was a little rough as I recall the steering wheel has a bit of a shake to it when it's just sitting in the driveway running...think there's something to that?

[iwillnc]

What year is it? if it's an 07+ 3.7l i5, then it should be smooth as butter, they are extremely smooth engines.

06, 3.5 was slightly rougher, but nothing "bad" by any sense

[jersey]

Yup. It's the 06 3.5.

It doesn't bother me too much, but it's there.

[HUMTECH]

Have you checked tire balance, front shaft u-joints?

[jersey]

Yup, checked the whole front end courtesy of lifetime alignment plan at Firestone. All was well there. Had all the ignition coils changed and that smoothed it right out.

I'm wish I could changed the title of this thread to Slow Death of a Hummer. After a month and a week of smooth rides here comes Death at my doorstep again. The car has started overheating reaching the 3/4 mark every day even after short rides. In February we changed the Thermostat out for factory new dealer replacement, also changed the belt and tensioner and radiator at the same time. This time Mechanic suggested the fan clutch because it seemed to move to freely when the car was off. I said ok, however two hours later when he tested it, the temp still came up. He got an exchange for the radiator we installed thinking the one in there was possibly defective; retested and the temp still came up. Pulled everything off the front of the engine double checked all his work and still is still scratching his head. He's going to replace the thermostat today even though its just a few months old.
He said "I hope it's not the head gasket".

I say, I see no loss of coolant whatsoever over the last few months since doing the radiator. No oil discoloration or mixing of fluids, no excessive tailpipe smoke. Nothing to really indicate an obvious head gasket problem. Hopefully it's just a faulty thermostat. Fingers crossed. Updates to follow.