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Is my 6.0L in need of a rebuild/replacement?

2K views 7 replies 5 participants last post by  shamrock12 
#1 · (Edited)
Here's my situation ... I have '02 2500HD with 6.0L that will be soon to roll over 100K miles. Being the original owner, I observed that during the first 35K miles that it does not burn a drop of oil. Then it has started to burn oil gradually. By around 70K miles it has started to burn coolant as well. There is zero visual leak anywhere at all, so I am pretty confident the motor are burning these fluids.

I have noticed that if I do alot of city driving (staying under 55 mph) that it would burn a quart every 2500-3000 miles. However, when I do alot of highway driving (65-70 mph), it would burn a quart every 700-1000 miles and continue to get worse :eek:

If I recall correctly, it burned a quart every ~1500 miles at 70k mark, every ~1000 miles at 80-90K mark, and now every ~700 miles at 100K mark. I am amazed that my catalytic converters have not plugged up yet!

So, is this clear-cut that my motor need to be rebuilt or replaced? I did replace the PCV valve awhile ago which made no difference.
 
#2 ·
It depends on where the oil & coolant are going.

Maybe do a compression test on all the cylinders. You could also use a video scope to look in each cylinder to check the cylinder walls, piston head and valves to see how they look.

Is there oil in the coolant and/or coolant in the oil?

If you are lucky, it might just be a failed head gasket, or maybe just a bad valve [less likely, as you are using both oil & coolant].
 
#3 ·
I just drained a bit of coolant from the bottom of radiator and did not find anything abnormal. Not sure if there is some coolant in the oil because I am constantly adding fresh oil. Would I need to pull both valve covers off to verify? If I do that, can I re-use the gaskets or would I need to install new ones?

Thanks
 
#4 ·
I would actually check one of the top radiator hoses for oil, as the oil should tend to float to the top, particularly when cold.

You probably should be able to tell just pulling off one cover, as for reusing the gasket, if it stayed in one piece when you took the cover over, probably would be fine with a bit of gasket sealant on it.
 
#5 · (Edited)
I have 60+ of these vehicles/engine all that make it well into the 200,000 mile range with my highest so far being 310,000 miles and still going strong. Our trucks are loaded down to the max and abused like -insert bad derogatory saying here-

What I have found is they all start burning oil around the 100k mark. Usually somewhere around 1/2 quart to a quart per 4000 miles. Around the 150k mark, that changes to a solid quart and at 200k, it can be almost 2 quarts. My 300k one (I still have and use) will burn (and leak a little) roughly 1 to 1.5 quarts per 1000 miles. The amazing thing is, the plugs look great and (so far) no cat malfunctions. :eek:

I have also had several that loose coolant for no apparent reason. Sometimes you really have to look closely for the leak at places like the heater hose to heater core quick disconnect nipple or even the water pump gaskets. These can be very tiny and will burn immediately on the hot surfaces, making them very hard to spot. I have also found the heater core leaking, but it will just come out of the HVAC drain, making it very difficult as well, to find. I figure the few I have had that I can't find the leak, were leaking from the heater core.

If you suspect the coolant is leaking in the engine, pull the oil cap and see if there is a lot of water condensating on the bottom side, then look down inside the fill tube to see if it is milky. If you pull a valve cover, the dr side one is the easiest and a replacement gasket is not a lot of money. Never use sealer, these are o-ring gaskets, not cork.

If you replaced the PCV valve, be sure to use the updated one that just has a small hole in the bottom, not the old school ones that have a spring loaded valve inside the case. GM did away with those years ago on these engines, due to high oil consumption. The new ones with the small hole, will never need to be replaced again. The GM part number I have written down (its old and might be updated by now) is 12572717.

Oh and your original question for rebuild or replace:
If it ain't broke, don't fix it. If it's running strong, the plugs are not oil/water fouling, the oil is still clean, the coolant is clean, no cat problems, ect I would run it till it becomes a problem.
 
#6 · (Edited)
I just went thru a month and a half long torture session for a bad missing/stalling problem with my 2003 Suburban 2500 with the 6.0L engine - and noticed something while in there that is potential source of coolant leak that I don't think a lot of people would notice.

I had serious running problems - and a cam position sensor code. So I pulled the intake manifold off to do the sensor. To remove the manifold I had to remove the small rubber crossover hose the pipes coolant thru the bottom of the throttle body. The damn thing would not come off - so I just cut it.

First observation: Coolant leaked out -and ran onto the top of the engine where it would run up against the intake manifold to head gasket.

If you had a small coolant leak at that point - it is likely going to get burned up by just dripping on the engine.

Second observation: The coolant could potentially run along the bottom of the head - and if there is a intake manifold gasket leak (vacuum leak) - you've got the potential for that coolant to just get sucked into the engine.

Apparently GM changed the intake manifold gasket design from the original (orange gasket surfaces) - to a better design ( teal gasket surfaces), because the intake manifold gaskets were a known issue.

I ended up using a Fel-Pro PermaDry problem solver gasket set which seemed very well made. And I made damn sure no coolant was leaking from that hose after I replaced it.

If you're going to inspect it - looking at the front of the engine you'll see a small "jumper" hose come off the bottom of the throttle body on the driver's side. This goes over to a crossover tube setup. Look around there for signs of coolant leaking.
 
#7 · (Edited)
I had an 00 6.0 that would use a 1/2 quart of anti-freeze ever oil change. I spent 3 years looking for the leak... to no avail! Come to find out that after I ran the truck hard and immediately shut it off, it would leak one squirt (just one) out of the lower water pump weep hole. It would never leak in any other situations, never! The truck died in a crash at 320k and the water pump was never changed...

I changed the oil every 3k and they never used more than 1 quart of oil, so no issues there.

Serviced regularly, these seem to be the best motors the General ever built. All 3 that I have had took a major tuneup at 100k, and I never really looked at them again. At 75-80k 2 took p/s pumps (a gm issue at the time) At 100k they need exhaust manifold gaskets, water pump gaskets and knock sensors. Somewhere at 150-175 an alternator and a/c pump. Somewhere, all 3 developed a lifter tick, but I never looked into it...
 
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