Coolant Missing, Running Hot, White Smoke, Burning Oil

[Brian Lamb]

I recently bought a 2004 Chevy Tahoe with the 5.3 flex fuel vortec engine on October 25, 2016. It had 154,000 miles when I bought it and now it has 158,000 miles.

I have had multiple issues with the vehicle in the short time that I have had it.

First off, when I start it, sometimes there is thick white smoke for the first five seconds at startup and then the smoke stops. It is a thick cloud of white smoke and smells like burning oil. I have to add 1-2 quarts of oil in between oil changes.

Also, when I first change my oil, the truck idles at 40 psi and pressure increases with the RPM's. After about 1,000 miles, the oil pressure drops to 20psi at idle and doesn't get above 40 psi during normal driving conditions. When I mat it, the pressure gets up to around 60psi.

I have also had an issue with coolant disappearing. There are no visible leaks of coolant. I have put two gallons of coolant in the truck within the past three weeks. When the coolant gets low, the heat does not blow hot and the engine temperature gets well above 210 degrees. I also hear a gurgling or boiling sound behind the dash board.

The truck runs smooth and drives like a dream but these are major issues that need to be addressed and need to be fixed.

Upon reading other threads, I have read that CASTECH has had manufacturing issues with the heads and that there is a possibility of a cracked head. I've also heard it could be the intake manifold gasket.

If anyone hsbhad this problem before or is having the problem, what could this be? Is it an easy fix? Hard fix? How much would it cost to get it fixed?

Thanks

 

[#1taho]

You can get a used 5.3 at any wrecking yard for $500. Sounds like you have a cracked head or head gasket.

If you like the truck I would change the engine. I wouldn't hesitate to mine if I had too

 

[iamdub]

If there's no oil in the coolant/coolant in the oil, then you are losing them separately. No fluids flow through the intake manifold on these engines, so I don't see how a leaking IM gasket would cause any of this. The oil consumption could actually be "normal" for your engine, especially if you run it hard. I'd treat the oil and coolant losses separately. Are you sure the "white smoke" is actually smoke and not steam? It could have a "burnt oil" smell because it's after a cold start so the engine is running rich. The rich exhaust smell mixed with the sweet smell of steamed coolant may be detected as burning oil. Or, it's actually not coolant and the valve seals are shot, allowing oil to leak and puddle into the cylinders then burn off the next time it's started.

I don't mean to offend, but many don't know the difference between steam and smoke and call anything floating in the air "smoke". Either one means two very different things. Verify what you have with us first.

A cracked head or failed head gasket and/or valve seals is likely. Worst case, barring the block being damaged/warped, is you'll need replacement heads, either used low-mileage or new/rebuilt ones. They're not all that involved labor-wise to replace due to the easy and "dry" IM removal. I have no idea on the cost of parts and labor.

 

[Brian Lamb]

If there's no oil in the coolant/coolant in the oil, then you are losing them separately. No fluids flow through the intake manifold on these engines, so I don't see how a leaking IM gasket would cause any of this. The oil consumption could actually be "normal" for your engine, especially if you run it hard. I'd treat the oil and coolant losses separately. Are you sure the "white smoke" is actually smoke and not steam? It could have a "burnt oil" smell because it's after a cold start so the engine is running rich. The rich exhaust smell mixed with the sweet smell of steamed coolant may be detected as burning oil. Or, it's actually not coolant and the valve seals are shot, allowing oil to leak and puddle into the cylinders then burn off the next time it's started.

I don't mean to offend, but many don't know the difference between steam and smoke and call anything floating in the air "smoke". Either one means two very different things. Verify what you have with us first.

A cracked head or failed head gasket and/or valve seals is likely. Worst case, barring the block being damaged/warped, is you'll need replacement heads, either used low-mileage or new/rebuilt ones. They're not all that involved labor-wise to replace due to the easy and "dry" IM removal. I have no idea on the cost of parts and labor.

The smoke is definitely smoke. The truck has water vapor from the exhaust but when it smokes it is a thick white cloud and it lingers for 30 seconds or more.

I was hoping not to be told of a cracked head, although I think that it what it is now.

 

[iamdub]

The smoke stopping after a few seconds after startup is indicative of worn/leaking valve seals, and that may be all it is. The coolant loss could be in the head(s). Since it's a dry IM, it's highly likely to be from a cracked head or failed head gasket. Either way, the heads have to come off so the head, IM and exhaust gaskets will all be addressed and you can replace the heads or have yours rebuilt or just cleaned and the valve seals replaced. Stock heads for your motor can be had relatively cheap from people upgrading to performance heads. It would be a great time to clean the oil out of the IM. As far as the rest of the motor, that mileage isn't high and the oil pressures sound normal. Fix the coolant issue before it gets worse and kills the motor and get a nice catch can.

 

[Brian Lamb]

Okay. So I've decided that I need a new engine after talking to friends of mine. My Tahoe has the L59, the flex fuel version of the LM7. Where can I get a rebuilt motor for my truck from with a warranty?

 

[Big Mama]

Lots of places. On the web you'll find direct engine replacements with lots or warranty. Trying to find one locally will save you shipping. GM offers direct replacements with warranty. All you'll need is the long block I assume you'll reuse your intake, exhaust and wiring. Even auto parts stores like Advanced have replacement engines with warranties. You might also find an engine builder in your area. There are tons of 5.3 motors out there.

 

[rockola1971]

Sounds like you are getting ahead of yourself. Id have the coolant system pressure checked and a engine compression test before I even thought of replacing the engine. The 5.3L is barely broken in at 158k. I have a 5.3L on my engine stand right now with 125k on it and the cross hatches look almost new on the cylinder walls. (Its a salvage yard engine i bought running and its going to get a bore and end up in my vette). Its very common for the 5.3L or any LSx platform engine to easily make it to 300K. I have a 6.0L with 294k on it and it runs strong. The days of the generation 1 small block dying at just over 100k are over. We have the Gen 3 and 4.

 

[SnowDrifter]

The intake manifolds on these rigs are dry. There's no coolant circulating through them

IMO your first steps should be the following:
Send a sample of your oil to blackstone labs to check for coolant contamination
While waiting for that, pressure test the cooling system and go over it with a fine toothed comb. Radiator, water pump, heater core, heater core connections, radiator hoses, overflow bottle, rear heater core lines, and rear heater core.
Also see if you cant rent a block tester from an auto parts store. It uses a CO2/Oxygen sensitive fluid to check for combustion gasses in the cooling system. It turns from dark blue to yellow.

Visually, do you have any coolant in the oil or vice-versa?

If you have access to a boroscope camera, you could pull the plugs and take a peek through each of the spark plug holes. If there's coolant getting into one of the cylinders, it will be clean. Normally your pistons will be black from carbon. Coolant steam-cleans it and leaves it looking darn near brand new - and as much as we all love shiny things, that's not a good thing in this case.


Depending on the results from that we can figure out what's going on

 

[retiredsparky]

You can buy a USB based borescope or small camera for around $20 online or at computer stores, they come in different cable lengths, and the camera is just some small led's around the lense, some as small as 5 mm in diameter. It just plugs into a usb port on a laptop. Remove the spark plugs, stick the scope in to check for clean pistons=the led's provide plenty of light to see the image on the laptop.

The combustion gas testing kits are also available for sale for less than 30 at auto parts stores. You pour some of the liquid into a special container that sits over the coolant filler in place of the reservoir cap. If the fluid changes color while the engine is running, that tells you there are combustion gases in the coolant. If not, the head gaskets are ok.