04 Tahoe 5.3-Z, repair/rebuild time; oil leak, coolant leak, intake gasket leak, axle seal leak, P01

[mattt]

2004 Tahoe Z71 4wd with a 5.3 and 227k on the ticker. It runs great and gets me everywhere I need to go. I've done basic maintenance, but I think it might be time to dive in a little deeper and give it some lovin' with the mileage on it. I've owned this vehicle since it had 140k, and it's been great, other than chewing thru tires and alignment issues.

Runs perfectly, but it has the typical 5.3 oil leak, a possible coolant leak, a possible intake manifold gasket leak, and a front axle(pass side) leak.

Last week on the way home from the mountains, 8000 feet, I had a CEL pop on for the first time ever. I was expecting some emissions code of some sort. Plugged in when I got home and it showed me P0171 & P0174, lean bank 1 and lean bank 2. Strange it was both sides, so I did some research, which points towards leaky intake manifold gaskets. My first thought was bad MAP sensor since it affected both sides/banks & I was on my way back from elevation and headed to sea level region, friend suggested fuel pump going out. I've driven a few times this week with reader hooked up so I could watch fuel trims, and I'm seeing LT fuel trims never dropping below +6, and going as high as +12 to +14 when sitting at a traffic light. Once on the gas and moving, it drops back to +6 to +8 range. Intake manifold gaskets?

Almost a month ago, I did an oil/filter change and reset the oil life monitor to 100%. I'm currently just under 70% and the "Check Oil Level" message has popped up in the message center on start up. This Tahoe has had the typical 5.3 oil leak for almost as long as I've owned it, but I suspect the oil leak has become much worse in the last month, as I've never had to top off oil this soon after changing the oil. I've been under it many times, and there has never been an obvious oil leak anywhere, just a bunch of small weepage from "who knows" that collectively made a mess, but never hit the ground and left it's mark. I'd like to hear from others that have fixed their oil leaks....what and where was it leaking? Asking so I can check all the usual suspects for oil leaks. Oil pan, rear cover, oil cooler block off, valve covers?

I've been adding Dexcool and distilled water on a somewhat regular interval for the last 6 months or so. On a cold day start up, there is a bearing squeak that is rpm dependent and rotational sounding. Have other people with a water pump on it's way out noticed a squeak...bearing maybe? Last year when I had the trans filter replaced at the dealer, they advised I needed a water pump. I also hear a water sloshing sound from inside the dash, possibly from water moving thru the heater core. I'm thinking all of this combined is pointing to needing a new water pump. Engine temp is rock solid at 210, gets up to temp quickly and stays there driving in traffic or highway, hot or cold outside. What have you heard or seen when a water pump replacement was imminent?

I'd like to think I'll tackle all these jobs at once, but I don't know that I do them all at once and be down that long. Is there anything else I should lay my eyes on when those jobs are going on, "since I'm in there that deep anyway?"

Front axle seal I'm thinking about taking in for the job, quoted $600 locally. I've read the threads where others have done it and just not sure I want to bother with it myself, messy job.

This really has been a reliable Tahoe, and I plan to keep it for another 200k for my mountain trips...unless I win the lottery or something crazy, Ha! What else have is "due" at 227k miles?

 

[VikingTrad3r]

On a cold day start up, there is a bearing squeak that is rpm dependent and rotational sounding. Have other people with a water pump on it's way out noticed a squeak...bearing maybe?

^^^

I have this exact thing two weeks after the very loud bearing noise on a very cold day for started I started haemorrhaging decks cool, I assume past the bearing. I did my change on boxing day easy job. It had been leaking for a long time. Lots of gunk buildup and stuck to the dampness around the water pump for about six months I've noticed the smell of coolant wafting from the engine bay after I shut it down. I Soum this was the decks cool is operating off of the block



was expecting some emissions code of some sort. Plugged in when I got home and it showed me P0171 & P0174, lean bank 1 and lean bank 2. Strange it was both sides, so I did some research,which points towards leaky intake gaskets

^^^

you need to know your fuel trim short term and long term on the scanner to be able to tell what the exact problem is. If you have a minor intake leak you are going to have a higher percentage of unmetered air at idle, which should manifest itself in the form of a higher fuel trim at idle. But then when you're out on the open road with your foot on the Excelerator the percentage of air coming in from your intake week will be so small that it will be barely noticeable to the computer to hold the 14.7 air to fuel ratio and therefore your trims will sort themselves out. If you go along Highway Drive your fuel trim should return.

There is a very good video by Schrodinger's box on YouTube about understanding fuel trims. If you have not watched it, Watch it.

Technically if you are getting on metre there somewhere after the air sensor it should affect both sides as your research has shown. But the way to find out is to take the car for a drive while being scanned and watch the impact of the small unmetered air leak become less relevant therefore have less of an impact on the fuel trim.

 

[mattt]

Thanks for the info on the water pump, and confirming. What does a water pump run for a 5.3? Has anyone had bad luck with an aftermarket pump? Factory one has held up for 12 years & 227k.

On a cold day start up, there is a bearing squeak that is rpm dependent and rotational sounding. Have other people with a water pump on it's way out noticed a squeak...bearing maybe?

^^^

I have this exact thing two weeks after the very loud bearing noise on a very cold day for started I started haemorrhaging decks cool, I assume past the bearing. I did my change on boxing day easy job. It had been leaking for a long time. Lots of gunk buildup and stuck to the dampness around the water pump for about six months I've noticed the smell of coolant wafting from the engine bay after I shut it down. I Soum this was the decks cool is operating off of the block



was expecting some emissions code of some sort. Plugged in when I got home and it showed me P0171 & P0174, lean bank 1 and lean bank 2. Strange it was both sides, so I did some research,which points towards leaky intake gaskets

^^^

you need to know your fuel trim short term and long term on the scanner to be able to tell what the exact problem is. If you have a minor intake leak you are going to have a higher percentage of unmetered air at idle, which should manifest itself in the form of a higher fuel trim at idle. But then when you're out on the open road with your foot on the Excelerator the percentage of air coming in from your intake week will be so small that it will be barely noticeable to the computer to hold the 14.7 air to fuel ratio and therefore your trims will sort themselves out. If you go along Highway Drive your fuel trim should return.

There is a very good video by Schrodinger's box on YouTube about understanding fuel trims. If you have not watched it, Watch it.

Technically if you are getting on metre there somewhere after the air sensor it should affect both sides as your research has shown. But the way to find out is to take the car for a drive while being scanned and watch the impact of the small unmetered air leak become less relevant therefore have less of an impact on the fuel trim.

Yes, I have watched that or another which explains LT and ST fuel trim reading. I know which is which on my handheld and I am seeing LT fuel trims adding fuel, mostly at idle. It is exhibiting what you typed, which is what is pointing me towards intake gaskets. It appears that there is an aftermarket gasket that is considered better than the factory hard gaskets?

 

[VikingTrad3r]

personally i get oem gaskets and then use hylomar as a gasket sealer. EVERY time. Never had a single re-do when i use hylomar as the gasket sealer and follow the application procedure.

Have you sprayed the brake cleaner or used a propane bottle yet to find the intake leak? You could also try the cigar smoke method through the brake booster vacuum hose.

you will need to tape off the throttle body intake for this method.

i found that a wife or a friend with a flashlight helps find the leak.


If it is truly a comprimised intake gasket then you might have trouble seeing it with the cigar smoke method.
also, you might get away with a quarter turn on the intake bolts tightening them.


VT

 

[mattt]

Thanks.

 

[mattt]

Update: Went back to the mountains last week, 8000 feet and cold, P0171 & P0174 lean bank 1 & 2, both returned. Which element leads to leans on both sides, the thinner air, or the cold temp doing a number on old gaskets. Which intake gaskets would others run, besides the OEM?

Also looked up OEM water pump on Gmpartsdirect.com. It shows discontinued on their site. Anyone have a recommendation or part # that is not discontinued. That is pretty lame of GMpartsdirect.com to have bad info, obviously there is a water pump still available.

 

[mattt]

Is there any other possible issue with 5.3's that could cause a P0171 & P0174 besides leaking intake gaskets?

Like to make sure before diving into the job.

 

[mattt]

I've been watching fuel trims on my handheld recently.

At what # of positive LT fuel trim enhancement is it advised to deal with the leaking intake gasket issue?

I am seeing sustained 6 to 8 LT fuel trim adding when driving. Pulling up to a stop light and idling, those fuel trim adding #'s go up to the 12 to 14 range.

Obviously it should not be adding that much fuel, so there appears to be a leak that is getting worse. I have also noticed fuel mileage dropping 1-2mpg recently.

 

[afpj]

Intake gaskets...felpro makes good ones.

Are you also looking at the voltages on the O2 sensors? If they look good, then what you describe points to vacuum leak, and at that age, if OEM, it's VERY likely intake gaskets. While your changing those intake gaskets, change the knock sensors and the oil pressure sending unit.

Water pump: look at rock auto. Change your Tstat as well. Think about changing hoses/belts