What did you do to your OBS GMT400 Tahoe/Yukon Today?

[east302]

Need to check it with a scanner, look for the coolant temp sensor (ECT) reading. The temp gauges on these are pretty much decorative. Most 400s seem to run about halfway between the low reading and the center reading.

I’d bet that you’re fine.

Nice Tahoe by the way.

 

[96-2D-Hoe]

I’d bet that you’re fine.

At least it crept up to 160 and stayed there, unlike the previous one. I also drove around for 20-30 mins and it didn't change at all.

I still feel like I'm down on power. I am pinging a little once in a while on the throttle going uphill and that could be the low (54PSI) fuel pump pressure / lean fuel air ratio.

I also often feel like my timing is out. Thought this for many years. Just doesn't seem to be firing right.

 

[east302]

At least it crept up to 160 and stayed there, unlike the previous one. I also drove around for 20-30 mins and it didn't change at all.

I still feel like I'm down on power. I am pinging a little once in a while on the throttle going uphill and that could be the low (54PSI) fuel pump pressure / lean fuel air ratio.

I also often feel like my timing is out. Thought this for many years. Just doesn't seem to be firing right.

Any codes or misfire counts?

 

[PG01]

At least it crept up to 160 and stayed there, unlike the previous one. I also drove around for 20-30 mins and it didn't change at all.

I still feel like I'm down on power. I am pinging a little once in a while on the throttle going uphill and that could be the low (54PSI) fuel pump pressure / lean fuel air ratio.

I also often feel like my timing is out. Thought this for many years. Just doesn't seem to be firing right.

I used to set timing like that, years upon years ago.... gun it up a hill and retard until no more pinging... bad gas will do it too.... no power, pinging...

 

[96-2D-Hoe]

Any codes or misfire counts?

Not bad, just seems off, and I can be fussy. Never misfires. I haven't checked for codes but I doubt there are any. I have a bluetooth gismo that a friend gave me I can check with. Smog test is due with registration in Sept so I've been meaning to take a look anyway.

 

[96-2D-Hoe]

bad gas will do it too.... no power, pinging...

I am guilty of buying cheap gas. But I can get as low as 6MPG without trying too hard

 

[96-2D-Hoe]

Washed, polished and waxed. The old girl has a few battle scars but still has good paint.

 

[east302]

.

 

[TheAutumnWind]

Just changed my thermostat as I didn't like the way it was operating. Would hit 200-210 depending on how I was driving, and then drop down to 170-180 and stay there. I had replaced the original with an aftermarket about 5 years ago along with an aluminum 3 pass rad, water pump etc. I decided to get a OEM Delco rated at 198 supposedly. But now operating temp on my gauge with the new 198 stat is showing 160. At least it seems to be steady at 160. But now I'm really confused. Pretty obvious the gauge is out but... Is this one bad? Was I way too hot before? It's not what I was expecting to happen.

Until you double check the gauge there is no way to know

 

[96-2D-Hoe]

I drove it 80-90 miles round trip along the coast / PCH to the dog beach, Leo Carillo. Such a pleasure to drive now, especially as rear brakes have no screeching, pulsing, locking up at a stop. Purred , and raced, along like a champ. Gave the trans a workout going up a couple hills and everything was working nicely. I also put slightly better gas in and I noticed no pinging, but the windows and the rear hatch were open all the way so I might not have heard it.

One thing I did notice yesterday that I can't say I ever noticed before in almost 20 years was while traveling in very slow moving traffic the truck would idle at 700-800 RPM and keep me moving along, when I stop it drops to 600 RPM. Never, ever seen or noticed that before despite sitting in plenty of traffic.

PS.
I stuck two Delco cooling system seal tabs in before I left as I've replaced a lot of coolant lately and I'm pretty sure it helps stop the intake manifold leak too much.

 

[jakcol997]

Painted my tow hooks red, just to give it some color in the front, then hoses out my evaporator cause my a/c air volume SUCKS. (Did nothing).

 

[My99Yukon]

After a summer of some wheeling in Colorado, I am starting the process of:
Engine Oil & Filter
Bleed Brakes & Fluid Exchange
Brake Pads & rotors
New Transmission Pan with Drain Plug
Transmission Exchange and Filter
Differential Fluid Exchange - Front & Rear
Steering Gear Fluid Exchange
Transfer Case Fluid Exchange
Shock replacement

I will put some separate comments in my thread. For example tonight, the process of purging the transmission system of the old garbage fluid rather than just dropping the pan and doing a transmission fluid and transmission filter change required a bit more thought and research. Fluid exchange. Transmission Fluid Exchange.

 

[96-2D-Hoe]

Until you double check the gauge there is no way to know

Just checked my ECT with a bluetooth OBDII reader. New thermostat hangs around 195 and shows 160 ish on my gauge. SO that means I was running around 220 and engine was hitting 250 before the stat was opening. No wonder my oil has been looking like crap after 1500 miles.

 

[96-2D-Hoe]

Flushed the power steering. Thought I'd try that before I change the pump. Fluid hasn't been in long but wasn't looking so hot.


I used a short piece/ 6" of 3/8 tubing folded to block the hard line, and 3-4' of 5/8 pushed over the other side to send the fluid to a catch can.


If you don't have a syringe a 'flavor injector' works great for sucking PS and brake fluid out of the reservoirs. I think I bought mine at the grocery store.

 

[96-2D-Hoe]

.

 

[96-2D-Hoe]

Changed the oil again. Didn't bother with filter as it was only changed a couple weeks ago. I was going to do transfer case also but the Wally World container doesn't fit my fluid pump. Washed out an empty coolant container so I can use that and will do it later in the week.

I've had a noisy lifter for years, back end of the passenger side. It got so noisy sometimes I was worried it was damaging the engine. I did a few quick oil changes with Wally World cheap synthetic and 1/3 can Seafoam last year and it has been much better. Oil was coming out black after a couple hundred miles. For too many years I was changing the oil every 3k, but that was taking me 1.5 - 2 years to hit. Realized my mistake and now try to change it every 6 months or so.
Recently the oil had been in for a year /1500 miles and I heard an awful racket a couple times from the top front / mid passenger side of the engine. I stuck 1/3 can seafoam in and changed the oil a few days later and I haven't heard that again. Lifter is still showing up quietly once in a while.
I had cooling issues a few years back and the engine got a bit hot a few times before I took care of it. Probably didn't help. That's been part of my reasoning for excessive oil changes.

Now I'm wondering if the high engine temp from the dodgy thermostat i swapped has been making the oil deteriorate faster. That's the main reason I changed the oil so quick, it was in for a couple weeks with the bad stat. I guess I'll find out from how it looks on the next oil change.

Happy wrenching.

 

[Sam Harris]

Changed the oil again. Didn't bother with filter as it was only changed a couple weeks ago. I was going to do transfer case also but the Wally World container doesn't fit my fluid pump. Washed out an empty coolant container so I can use that and will do it later in the week.

I've had a noisy lifter for years, back end of the passenger side. It got so noisy sometimes I was worried it was damaging the engine. I did a few quick oil changes with Wally World cheap synthetic and 1/3 can Seafoam last year and it has been much better. Oil was coming out black after a couple hundred miles. For too many years I was changing the oil every 3k, but that was taking me 1.5 - 2 years to hit. Realized my mistake and now try to change it every 6 months or so.
Recently the oil had been in for a year /1500 miles and I heard an awful racket a couple times from the top front / mid passenger side of the engine. I stuck 1/3 can seafoam in and changed the oil a few days later and I haven't heard that again. Lifter is still showing up quietly once in a while.
I had cooling issues a few years back and the engine got a bit hot a few times before I took care of it. Probably didn't help. That's been part of my reasoning for excessive oil changes.

Now I'm wondering if the high engine temp from the dodgy thermostat i swapped has been making the oil deteriorate faster. That's the main reason I changed the oil so quick, it was in for a couple weeks with the bad stat. I guess I'll find out from how it looks on the next oil change.

Happy wrenching.

Have you ever considered an engine oil analysis from Blackstone? It’s a great way to tell you what is really up with the engine. And definitely worth the small cost.

https://www.blackstone-labs.com/?se...abs.net/Bstone/(S(ypq2mcjdiivdlsbxd53oqv45))/

 

[96-2D-Hoe]

Have you ever considered an engine oil analysis from Blackstone?

I haven't. Engine only just hit 107k. I think/hope it's mostly related to what I already mentioned. The tick only happens at idle and a stronger idle has helped. I know a lot of the engine is aluminum etc but I have an aftermarket drain plug with a strong magnet and it's surprisingly picking up very little / basically nothing. At worst a coat of sludge.

Thanks for the suggestion. I'll keep it in mind.

 

[liquify33]

Adjusted rear brakes and replaced rear shocks. Getting her ready to sell. Kinda sad about that it’s a great truck

 

[Tonyrodz]

Adjusted rear brakes and replaced rear shocks. Getting her ready to sell. Kinda sad about that it’s a great truck

So why sell it? Upgrading?