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I don't get into the internals.. I've replaced a head gasket before.. Not something I really want to do again. I've noticed that I'm getting to the point where I'm having to add about two quarts of oil every 3k miles.
Initially, I thought I had blown a rear main seal, because I did have a transmission rebuilt about 100k miles ago and that's about when all this started.. Took it to my guy and put it up on the rack.. We looked all over, there's no oil leaking. Engine bay is clean enough to eat off of.. Nothing coming out the bottom, either.
Now.. I had noticed a small amount of smoke on startup in the mornings, after it had been sitting.. Having 240k miles, a little leakage from the valve seals wouldn't be unusual. But the amount of smoke vs the oil being lost.. I thought there had to be something else going on.. My guy told me i'm too old and that it wasn't that odd to not see a whole lot of smoke in these cases with modern vehicles.
Seeing everything clean.. There's only one other place the oil is leaking.. And that's internally. So.. I know that alot of people immediately would say "240k miles.. Time for it to go".. I don't want to do this for several reasons.. First.. I like the truck. It's a 2005 Colorado. You just can't get them like that anymore. It's a standard cab.. Does have the I-4 which isn't rare, but it was towards the end of the true "Light Truck".. Second, I don't really want to buy something else.. I want to get another 3-4 years out of it at which time my house will be paid off, then I'll buy something new, and I hope to gift this truck as a first vehicle for a relative. And I really, really want to get 300k miles out of this thing. Just to say I got 300k miles out of a vehicle.
Smoke on startup after sitting and 240k miles.. I think we can safely assume valve seals. But.. The concern I have.. Is there more? If we not only have seals leaking, but also the rings are worn.. That may push me to the "Keep oil in it and run it until it blows up" thought process. This being one of the Vortec 2800 engines.. These things did have problems with valves (TSB 07123A).. So, there's a possibility of it needing more than just the seals, but it's running fine, so.. I don't really think that's going on. No more wear than is normal for 240k miles.
Just looking for thoughts. What would you do to verify that it's only valve seals? Would you just bite the bullet, have the head pulled and a valve job done if it was confirmed as only in the top end? Just ride it out and keep it topped off?
The issue is probably not mechanical but the motor oil you are using. Please don't start with the synthetic crapola. Research the ASTM D-5800 test and what it is and why it's probably the cause of the issue. AS any engine gets older with miles, the internal heat starts to build as combustion gases which can hit 1100F are now going around worn rings. The oil is literally cooking inside the engine. The coolant, while probably still showing no visible signs of an overheat, is still able to handle the "coolant" temperature. That's not the same as the core temperature which may now be double the design specs. This is why most auto makers are now monitoring Engine Core Temps. The ASTM D-5800 test runs the oil at 250C which is 482F for one hour. The amount of oil cooked off in that hour is represented as the percentage of weight lost in the test. Mobil One in 5w-30, for an example, is 10.4 or 10.4 % of it cooked off due to high heat. If you look at the lowly Pennzoil conventional 10w-30 in the cheap yellow bottle, its rating is 4.2. Yep, no typo here folks, the conventional not only beat the synthetic crap it did it by almost 250%. So much for synthetic oil and high heat "protection". You can do the research at the PQIA website.
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Just looking for thoughts. What would you do to verify that it's only valve seals?
A normal running temp cylinder leak-down test would reveal if there were problems with rings or valves. A borescope inspection could reveal cylinder wall scoring, burnt valves, or similar mechanical damage. If the inspections appear OK, then you've now isolated the oil consumption to coming past the valve stems. But bear in mind that this could be due to excessive wear in addition to failed valve seals.
Would you just bite the bullet, have the head pulled and a valve job done if it was confirmed as only in the top end? Just ride it out and keep it topped off?
If the truck is otherwise in good running order and condition except for the oil consumption, I'd get a quote on a valve job. Then you can make an informed decision about the value to you of keeping the truck on the road. Compare this cost to adding a quart of oil every 1,500 miles for your projected lifespan of the truck.
You may be dollars ahead by "riding it out" ... at least until the engine is so worn out that it drops off in fuel economy and high oil consumption. Then you can make a decision about whether or not it's worth it to you to keep the truck on the road.
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The engine's an air pump, its two main sealing areas are the valves and the piston rings. Doing a valve job on a 240K engine may well result in highlighting any weakness in the rings when the valve seal is made tighter.
Any competent mechanic should be able to replace the valve stem seals without removing the cylinder head. Of course, if any valves are leaking, a complete valve job is required to stop those leaks. The cylinder head must be removed for that.
Personally, If I wanted to keep the truck, I would be looking for a rebuilt long block to install in it. That should solve any and all problems!
The nice thing about valve seals - it is no different than doing a head gasket. In fact if you do a head gasket you normally replace the valve seals at the time. Pull the hear, take it to the shop give them the seals. Most of the time you are going to the shop anyway to get the head re-surfaced. The shop I use charges $24 to do valve seals if you supply them.
For other people, if you pull the head for any reason - just replace the valve seals. There is no reason not to unless they are basically new, but if it is basically new then why are you pulling the head? If it overheated, replace the seals. It is no worth pulling the head again to save $24 (plus the minuscule cost of the seals).
Run some high milaege oil in it for an oil change and see if it makes any difference. It didn't help my 87 Firebird, but it's also a 30 year old engine.
It wouldn't hurt to have a compression test done too, just to see how much piston ring wear you have.
Do a leak down test to see your compression figures. That will tell you if the rings are shot.
Replacing the valve seals should be fairly cheap to do, and I'd argue that since we're only talking an I4 here, an engine rebuild would be pretty cheap as these things go too. Do the leak down test and go from there.
The issue is probably not mechanical but the motor oil you are using. Please don't start with the synthetic crapola. Research the ASTM D-5800 test and what it is and why it's probably the cause of the issue. AS any engine gets older with miles, the internal heat starts to build as combustion gases which can hit 1100F are now going around worn rings. The oil is literally cooking inside the engine. The coolant, while probably still showing no visible signs of an overheat, is still able to handle the "coolant" temperature. That's not the same as the core temperature which may now be double the design specs. This is why most auto makers are now monitoring Engine Core Temps. The ASTM D-5800 test runs the oil at 250C which is 482F for one hour. The amount of oil cooked off in that hour is represented as the percentage of weight lost in the test. Mobil One in 5w-30, for an example, is 10.4 or 10.4 % of it cooked off due to high heat. If you look at the lowly Pennzoil conventional 10w-30 in the cheap yellow bottle, its rating is 4.2. Yep, no typo here folks, the conventional not only beat the synthetic crap it did it by almost 250%. So much for synthetic oil and high heat "protection". You can do the research at the PQIA website.
So you're comparing a 5w synthetic vs a 10w conventional and thinking that's a fair comparison? LOL
Sorry, synthetic oil is superior in any FAIR test you put it up against a conventional oil.
So you're comparing a 5w synthetic vs a 10w conventional and thinking that's a fair comparison? LOL
Sorry, synthetic oil is superior in any FAIR test you put it up against a conventional oil.
Superior but unnecessary in most cars. However for leaking seals it is not as good as thick dino oil.
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