(Duh duh DUH!) Burnt my valves

[MENTION=115347]gamefreakgc[/MENTION] Yeah, I bought my wife an older RX300 so she's set if I need to borrow it, and my folks have a beat to crap dodge I can borrow for the time being. I'm thinking the timing belt looks like the hardest part of this job, but there are enough write ups that I think I can puzzle my way through it.
And to cater to my ignorance, will the valve adjustment be a separate service apart from my head rebuilding?
 
I think I'd seek a 2nd opinion on this one. It's very hard for me to believe you have a bad valve with 100k miles on the truck. That's usually caused by running lean for a long time, and that's just not a very likely scenario with this engine at that mileage.

I'm not saying it's impossible, just very unlikely.
 
It is kinda weird. I know the PO said he crossed over the 100k mark when moving to Kansas from Texas, so it had at least one long road trip on it while having this issue.
I'd definitely be happy if this proved to be something less drastic though.
 
Take off the passenger side valve cover and see what the internals look like. If the valve(s) is burnt my guess what lies underneath the cover could be a real mess (not changing the oil enough).

I am in the same boat as Jeremy though, I just don't believe it is a burnt valve without major abuse in the first 100k miles. Spend the $$$ for a second opinion. If you want a semi redneck way of checking for a burnt one, warm the 4runner up to operating temp, go back to the exhaust and stick you hand almost right on the tailpipe. If you feel your hand could be almost sucked into the tailpipe, even barely, then yep, a burnt valve(s) is quite likely. I have never done this on a 4runner but it has worked for me in other applications.

Did your mechanic perform a compression and/or leak down test?

Also, the timing belt change on this engine is cake in comparison to the rx300.
 
solsnowbarger said:
[MENTION=115347]gamefreakgc[/MENTION] Yeah, I bought my wife an older RX300 so she's set if I need to borrow it, and my folks have a beat to crap dodge I can borrow for the time being. I'm thinking the timing belt looks like the hardest part of this job, but there are enough write ups that I think I can puzzle my way through it.
And to cater to my ignorance, will the valve adjustment be a separate service apart from my head rebuilding?
Click to expand...

Unfortunately, probably not. When you've got the new cylinder heads back on you'll need to measure the gap between the camshaft and the shims that sit on top of each valve. If the gap is too small, they will stay open (and eventually burn the valve). Too wide and it won't open enough and cause a different set of scenarios. You can't adjust the gap, what you have to do is remove the shim and calculate the size you need to get the desired gap. It's not as hard as it sounds, just tedious. Getting the shims out takes a steady hand and the right tools.

Out of spec valves can cause misfire codes or lean/rich codes. But I do agree with others, valves RARELY go bad on these engines. I checked my valve clearances on mine with 190k miles when I got it and they were all perfect, like it had just come off the factory floor. But, it is possible.

LittleCaesar said:
Take off the passenger side valve cover and see what the internals look like. If the valve(s) is burnt my guess what lies underneath the cover could be a real mess (not changing the oil enough).

I am in the same boat as Jeremy though, I just don't believe it is a burnt valve without major abuse in the first 100k miles. Spend the $$$ for a second opinion. If you want a semi redneck way of checking for a burnt one, warm the 4runner up to operating temp, go back to the exhaust and stick you hand almost right on the tailpipe. If you feel your hand could be almost sucked into the tailpipe, even barely, then yep, a burnt valve(s) is quite likely. I have never done this on a 4runner but it has worked for me in other applications.

Did your mechanic perform a compression and/or leak down test?

Also, the timing belt change on this engine is cake in comparison to the rx300.
Click to expand...

If the valve cover is off, you could measure the valve clearance too. A burnt exhaust valve will be out of spec. But a leakdown test will tell you the same thing.
 
I would definitely get a second opinion on a babied 100k mile 4Runner having "burnt valves". I'll be that guy and say that a JDM engine is a great option if you buy from a reputable vendor. Change all the gaskets and do the timing belt before installing so that you get a good look inside the engine. Water pump will need to be changed regardless since it is different on the JDM 5VZ. I've dealt with a bunch of engines from JDM Engine Zone and all have been flawless. I'd recommend a JDM over some shitty Jasper rebuild any day.
 
solsnowbarger said:
And yes, neglect is what I'm thinking as well. It all looks so clean though! The lady even covered her mats in plastic bags! Haha sneaky old ladies are the worst.
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Old lady cars are the worst. Sure they have low miles, but that's only because they've been driven 2-3 miles at a time. Low miles isn't always a good thing.

Good luck with everything, and I hope that you find some happiness amidst the silliness of the situation.
 
T4R2014 said:
I would definitely get a second opinion on a babied 100k mile 4Runner having "burnt valves". I'll be that guy and say that a JDM engine is a great option if you buy from a reputable vendor. Change all the gaskets and do the timing belt before installing so that you get a good look inside the engine. Water pump will need to be changed regardless since it is different on the JDM 5VZ. I've dealt with a bunch of engines from JDM Engine Zone and all have been flawless. I'd recommend a JDM over some shitty Jasper rebuild any day.
Click to expand...

Doesn't Jasper though have a pretty decent warranty on their rebuilds?
 
first, how bad is the miss?

second, I would also suggest a 2nd opinion.
then I would pay(or do it yourself) to have the valves adjusted. perhaps its just a bit tight and not closing all the way.

3rd, how bad is the miss?
if the valve adjustment checks out, and the miss isn't too bad, why not just keep driving it?
 
solsnowbarger said:
They called back with the diagnosis of burnt valves,
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All cylinders? My biggest concern if it were me with just 100k miles is trying to figure out the source of the problem. You just don't get burnt valves at 100k without a reason. Replacing the heads or rebuilding the heads might only be a temporary fix. You might find yourself back on the forum again in another 100k with the same problem.

Could try running a cooler plug to prevent pre-ignition, check for any vacuum leaks, send your fuel igniters off for cleaning, using 92 octane for a few fill ups, and all the "other stuff" before jumping into a new engine or heads. A small vacuum leak that's gone un-noticed for a long period of time will cause detonation. How's your cooling system? T-stat, new coolant? Using Toyota red? All of these things are worth checking.

If it's just one cylinder, then hey, valves go bad. They're made by men. If so then just remove the one head and have the valve replaced with the work that goes with it. No need to rebuild the heads. Just my opinion. Make a list and start checking things off. Somethings not right.
 
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