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What did you do with your GMT400 today...or yesterday....

Here ya go…. Watch the tensioner and belt start moving towards the inside of the pulley at 1:18. I was pouring from a water bottle

 
I would start with ensuring the pulleys are EXACTLY even. And with belt off see if there is fore/aft free play in the tensioner arm.

Don’t change just the pulley or bearing. You need the entire tensioner assembly.
I normally replace idler pulley when I do tensioner pulley.

I was scrubbing the video slowly from the 15 second to the 20 second mark. Do that and watch the front edge of the belt compared to the and you can see the belt tracking foreword and backwards in comparison to the grooves of the pulley below it.
Something is trying to drive that belt rearward.

Either
1. the alternator or the a/c compressor could be pulling it rearward and there is enough traction on the tensioner pulley to keep bringing it foreword. Then when it gets wet it looses traction to pull foreword and the belt is pulled back off it.
Or
The arm of the tensioner is worn and the fulcrum (bolt it swings on) is at a slight angle, or the bearings are shot allowing the pulley to pivot on them so the pulley is no longer flat, but nose down.

If you change the tensioner pulley assembly and the a/c / alternator is out of alignment, it might work for a while then fail shortly after because the paint on the pulley can help it stay put at first. Then as it wears begin slipping in the rain again. So verify alignment.
 
Well I made it to work this morning! Plus had tools with me, tried to leave early so if it jumped off I wouldn't have to call in late.

AC compressor was new with clutch, I did check the pulley along with the PS pump and vacuum pump too last night. looked on RA for the Delco tensioner. $35 + shipping. I may do that. I did notice that looking at the other brands they listed that the pulley on them were narrower, the Delco showed a wider pulley. my tensioner is a GM one seeing the numbers stamped on the aluminum but that doesn't mean someone replaced the pulley at one time.

I almost tried to install my old spare belt to see if it helpd, but I remembered that one of the ribs on the end had torn off so I scratched that idea. looking like this one will become my spare while I get a new belt and tensioner then go from there.
 
And even though the current tensioner assembly has a GM P/N on it, you have no idea how old it is. While the tensioner spring may still be strong, you don't know how much wear (until the belt is off and the tensioner spring disconnected so the arm is under no tension) is in the arm's pivot until you try to see if there's any play in any direction other than pivoting - there should be zero deflection in any direction, just smooth, tight rotation throughout it's entire range. Especially check it where it normally rides, as this will be the greatest wear point. ANY deflection is bad, as that can throw the belt off.

Same with the pulley. The PO may have gone the cheap route and just pressed out and pressed in a new bearing in the tensioner pulley, but was it the right one? Yes, it may be the correct "size", but the suffix letters on a bearing's P/N indicate if it's shielded on one or both sides and whether or not it designed to be waterproof. There should be absolutely NO play whatsoever in the pulley bearing and it should rotate smoothly with no rough spots. It may look fine while running with no wobble because it's under tension, but that film of water between the pulley and the back of the belt can be enough to deflect the pulley a few thousandths - which is enough at idle speed to throw the belt.

I find it strange that puddle splashes keep throwing your serpentine belt. I've never encountered that with either my '94 or '98, both past 200K miles, when hitting big puddles, standing water, or big snow drifts. I've even power washed the Burb's engine while it was running and blasting clean the front of the motor definitely got high pressure water all over the belt, tensioner, idler, vacuum pump, etc. and I've never thrown a belt.
 
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Video of my ‘99 on cold start up at 40 F. Starts instantly, but takes a bit for the white smoke to clear up.

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
youtube.com youtube.com

This is what the internet says:

1. White smoke on a cold start, and then it disappears as the engine warms up
This is very common. It will often happen at startup in cold weather with lower compression engines. As you start running the engine at idle (around 650 or 750 rpm), you will achieve a more effective compression ratio, and the smoke clears. White smoke has a lot to do with the temperature in the combustion chamber.

If the smoke is really just a puff, there is not much to worry about. Especially if it has been sitting, it could just be built up condensation.

If it lasts a few minutes after the engine is started and there is a rich diesel smell, 👃 they may be some cause for concern. Some of the likely causes include,

  • Faulty injectors - stuck open.
  • Worn piston rings or cylinder glazing
  • If equipped with glow plugs, could be faulty plugs or module.
Remember, if you have an older engine with really low compression and bad timing or low injection pressure, you are more likely to have white smoke.

So I've replaced Glow Plugs and the harness. Injectors soon to be replaced as it's time.
 
if you have an impact screw driver (type you use a hammer on) , try using a chisel point bit. I've had to grind a flat git into a point before. that might be able to dig into the head and grip it without having to cut a slot. might be just enough to break it loose and thread it out.
 
dbrannon79 said:
if you have an impact screw driver (type you use a hammer on) , try using a chisel point bit. I've had to grind a flat git into a point before. that might be able to dig into the head and grip it without having to cut a slot. might be just enough to break it loose and thread it out.
Click to expand...

That's what I have (down in Fullerton). This is an better idea.
 
if you can get a drmel in there straight up n down to the head, home depot sells a tiny carbide bit for de-burring. I bought one of those myself. those little buggers can carve some meat lol depending on how thick the face of the pan is once you grind the head off and pull the pan then you'll have access to use vice grips to get it out

that pan being aluminum most likely is fairly thick in the gasket mating surface to bolt head. and I'm almost betting that area is where it's seized and not the threads.
 
Big T said:
Video of my ‘99 on cold start up at 40 F. Starts instantly, but takes a bit for the white smoke to clear up.

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
youtube.com youtube.com

This is what the internet says:

1. White smoke on a cold start, and then it disappears as the engine warms up
This is very common. It will often happen at startup in cold weather with lower compression engines. As you start running the engine at idle (around 650 or 750 rpm), you will achieve a more effective compression ratio, and the smoke clears. White smoke has a lot to do with the temperature in the combustion chamber.

If the smoke is really just a puff, there is not much to worry about. Especially if it has been sitting, it could just be built up condensation.

If it lasts a few minutes after the engine is started and there is a rich diesel smell, 👃 they may be some cause for concern. Some of the likely causes include,

  • Faulty injectors - stuck open.
  • Worn piston rings or cylinder glazing
  • If equipped with glow plugs, could be faulty plugs or module.
Remember, if you have an older engine with really low compression and bad timing or low injection pressure, you are more likely to have white smoke.

So I've replaced Glow Plugs and the harness. Injectors soon to be replaced as it's time.
Click to expand...
That's a whole lot of smoke! how cold was it when you filmed your video? that could definetly be an injector leaking. does it still smoke after warmed up and then let sit for maybe 30 minutes to an hour?
 
dbrannon79 said:
That's a whole lot of smoke! how cold was it when you filmed your video? that could definetly be an injector leaking. does it still smoke after warmed up and then let sit for maybe 30 minutes to an hour?
Click to expand...

Temp was 40 F.

Letting it sit 30 after warm-up, not much smoke. Just a light puff on start-up.

I’m thinking injectors leaking. I have a new of Bosch from Leroy that I just bought.
 
I poked remanned Bosch units, from Oreilly, into My 6.5 and it has a small puff of white smoke on startup.
The colder the temps, the mor smoke it puffs out.
That lasts for several seconds then its down to just exhaust.
I even advanced the timing a notch or ten. I thingk it was -.43 and now it is -1.53 or some such. It still blows its puffa white smoke. 😹😹😹
I’ll live just fine I figure.
 
MrMarty51 said:
I poked remanned Bosch units, from Oreilly, into My 6.5 and it has a small puff of white smoke on startup.
The colder the temps, the mor smoke it puffs out.
That lasts for several seconds then its down to just exhaust.
I even advanced the timing a notch or ten. I thingk it was -.43 and now it is -1.53 or some such. It still blows its puffa white smoke. 😹😹😹
I’ll live just fine I figure.
Click to expand...

My wife loves to do road trips for her geocaching. She has a goal to find a geocache in every county of Montana. So we’ll probably make a road trip out your way and return the IP.
 
Big T said:
My wife loves to do road trips for her geocaching. She has a goal to find a geocache in every county of Montana. So we’ll probably make a road trip out your way and return the IP.
Click to expand...
That would be great. Be looking forwards to that.
There is no hurry, so far the old beast is doing just fine.
Might be someone else needs to do a diagnose, then off again it’ll go. 😹😹😹😹
 
Big T said:
Temp was 40 F.

Letting it sit 30 after warm-up, not much smoke. Just a light puff on start-up.

I’m thinking injectors leaking. I have a new of Bosch from Leroy that I just bought.
Click to expand...

Do them asap if so. Leaking ones quickly turn into ones that shoot a fine stream. And if that stream shoots through the opening of the precup, it can put a hole in the top of the piston.

I would want to put a volt meter on each of the glow plugs however. It is hard to imagine 20-25 seconds of that much smoke from one or injectors leaking down. Looks like you started truck, walked around, then started recording. In the 5 (?) seconds before the recording as you start it- does one or two of the cylinders not start working? It would be a very noticeable misfire for a few revolutions while the ip fills the lines back up.
 
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