Cracked valves

[mendozer]

Almost 8 months ago now, I was on here trying to test why I was getting misfires. Did fuel injectors, valve cover gasket, spar plugs, wires. Then did a leakdown test and found low compression of cylinders 4 and 6 and crossover during the leakdown. So I thought "oh great head gasket".

I've been tinkering with it for the last week or so, struggling along the way with the crank nut and certain angles of things, sawing off an exhaust nut, etc.

Only to arrive to this today...cracked exhaust valves of cylinders 4 and 6. I didn't see any obvious head gasket failure between the two, nor was there coolant in the cylinder (although it hasn't been driven in a while). I still haven't gotten the passenger side off yet (stuck instet hex bolt) but I didn't have pressure issues there so I don't expect to find anything weird.

I was going to take the heads in for pressure testing, washing, etc for $150/head but now...I expect that labor to be much higher. He initially was going to charge me 975 for both heads fully rebuilt assuming it all needed to be done.

I can get a remanufactured head for about $325 online from a reputable spot. So if I forgo the "but it's my engine" emotion, I can get both heads shipped to me for $700. then it's just bolt on and be done with it.

I am going to rebuild the third member too so there's $700 out of my pocket on top of this.

I come to you gurus with these questions:

1. how do these valves crack?
2. Does it matter if I put rebuilt heads in with camshafts and valves that weren't originally in there? I imagine all parts are swappable but there's always that little bit of "preference" or history with originally mated parts.
3. I only have 172k on there, and I've owned it since 130k. So as far as the whole vehicle goes, it's just stretching out. I'm hoping I can take it to 300-350.
4. Would YOU do a repair on the three valves and nothing else or bite the bullet and do the whole rebuild? After all, my quote for the head gasket repair was $3200 from a shop, hence why I tackled this myself.

 

[Dieselchessy]

Bad MAF or O2 sensor causing it to run lean?
Would expect the plugs to show a lean condition for some time before scorched valves unless it was a short term high stress situation.

Could be other things.

Is it boosted, or have an open exhaust?

 

[mendozer]

Not boosted. Exhaust has a rusted hold (at the muffler) but otherwise no. Never had O2 codes, and MAF was cleaned probably 2 or 3 times in the 5 years of ownership, again no codes. It started with one misfire, then as tie progressed multiple. Then we confirmed coolant in the exhaust I believe.

 

[Dieselchessy]

Coolant in exhaust?

Is the head cracked as well, or bad gasket?
These things have a tendency to crack the heads between the valves.

 

[mendozer]

I meant exhaust compounds in coolant aka block tester. Sorry my words got switched. I assume the gaskets bad due to mileage but it didn't look horribly bad. No obvious failure esp between the cylinders. I didn't clean it yet

 

[Coward]

Any pinging or knocking prior to all this when driving?

 

[19963.4lsr5]

Toyota is not good at detecting missfire. It really looks like it was run lean for a good while.

Sad thing is with only one fuel bank as injectors clog or whatever the O2 sensor richen up all cylinders. To try and make up for it. You only get the system too lean code when it can’t throw anymore fuel at it. A few cylinders may end up being really rich and a few or 1 cylinder be really lean........


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[mendozer]

I didn't notice anything, but I'm also not experienced with those things. The technician that initially quoted me listened to it in the parking lot and said "yup I hear it, you're head gasket". I don't know what he was hearing. I can tell you right now I have a Honda with a head gasket issue and it rumbles upon startup, this never did.

 

[mendozer]

Toyota is not good at detecting missfire. It really looks like it was run lean for a good while.

Sad thing is with only one fuel bank as injectors clog or whatever the O2 sensor richen up all cylinders. To try and make up for it. You only get the system too lean code when it can’t throw anymore fuel at it. A few cylinders may end up being really rich and a few or 1 cylinder be really lean........


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Interesting. Well in my steps taking before this, I did put in new injectors so I'm good there. my MAF has always been cleaned, I suppose I could test the O2 sensor. Which one would it be?
Also, in theory how long can it run cracked?
I ask because during all this when I pulled the valve covers off to do gaskets I saw the dirtiest valve covers imaginable. I mean baked on black. Now they're grey and spotless but it took a lot of soaking in Purple Power concentrate and scrubbing to get there. Could that be from something in the past relating to this issue? It has never overheated severely in my care. I say severely because in the mountains I'll get coolant temps on my ScanGauge of 230+. Since then I did put in a better radiator and I have a new fan clutch to go in as well.

 

[mendozer]

they're not that old because I did them with the injectors, but spark plugs 4 and 6 were still clean white where the others had some brown residue. Look at that, the more you learn on here!

 

[gamefreakgc]

Burnt valves are more common than you might think. I've personally owned 5VZ-FE with burnt valves but it usually happens with 200K+ miles. It is usually a result of a lean condition.

To answer your questions:

1. I think this has been answered.
2. The valves will need to be adjusted either way. This is done by removing the little "hockey pucks" that sit in the buckets right under each cam lobe. The shop is including the price as that's part of a valve job. If you buy new heads instead you'll have to buy more shims (they are $10 each) and do the work yourself which takes some time and a lot of patience.
3. Is this a question or a statement? By 300K every suspension and steering part will need to have been replaced. Normally the engines last longer.
4. I would not rebuild the engine. You found the problem, fix the valves and the whole thing will have new life again.

 

[mendozer]

darn the local guy won't come down in price. I see some rebuilders say they grind valves with three angles, some say 5 angles. Do these runners require something specific?

 

[Coward]

Burnt valves are more common than you might think. I've personally owned 5VZ-FE with burnt valves but it usually happens with 200K+ miles. It is usually a result of a lean condition.

To answer your questions:

1. I think this has been answered.
2. The valves will need to be adjusted either way. This is done by removing the little "hockey pucks" that sit in the buckets right under each cam lobe. The shop is including the price as that's part of a valve job. If you buy new heads instead you'll have to buy more shims (they are $10 each) and do the work yourself which takes some time and a lot of patience.
3. Is this a question or a statement? By 300K every suspension and steering part will need to have been replaced. Normally the engines last longer.
4. I would not rebuild the engine. You found the problem, fix the valves and the whole thing will have new life again.

I burned a valve on mine at 370k. For years I had pinging issues from time to time along with someone hesitant acceleration. I had my heads rebuilt and runs amazing to this day (+50k). I assumed the reason for burned valve was carbon buildup and a small piece caused the valve damage. I agree though. Rebuild the heads you have. I paid $680 I think here in NC for machine work which included a gasket set.

 

[gamefreakgc]

darn the local guy won't come down in price. I see some rebuilders say they grind valves with three angles, some say 5 angles. Do these runners require something specific?

Standard 3-angle valve job is sufficient. Not going to notice a difference, fancy valve jobs are for all-engine power builds which would be a waste of time with the 5VZ-FE since it responds so well to boost. Cheaper with a 3 angle anyway.