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Hi guys. Im working on my friends truck so his daughter can take it back to college, but I’m kind of stumped and hoping someone here can shine a light for me.

2007 Titan, flex fuel, 149k miles, burns a half quart every couple of tanks, smokes on startup. Mildly low on coolant but has never added any since new.

Problem presented as cylinder 3 misfire. I moved coil packs and fuel injectors, misfire stayed with the hole. Cat glows red so I was thinking maybe clogged cat until I did a compression test and found no compression on cylinder 3 at all. We did a leak down test and here’s where it gets weird. I didnt know how to make sure the cylinder was at the top of the compression stroke so I ran the test at the top of both the compression and exhaust strokes. Here are my results:

Test 1 - small amount of air from vacuum port behind throttle body, larger amount of air coming from cylinder 1 spark plug hole

Test 2 - no air from vacuum port, similar amount of air coming from cylinder 5 spark plug hole.

I’m learning on DOHC engines here, my wheelhouse is pushrod engines so please bear with me. I’m leaning towards a cracked block across cylinder 3 allowing compression to bleed to 1 and 5, but that doesn’t tell me why it didn’t leak from 1 and 5 at the same time. I can theoretically attribute that to piston 1 and 5 placement based on the stroke I was testing cylinder 3 at but I’m not certain.

Have any of you had any similar issues? Have you had blown head gaskets that acted like this? Is this thing a beast to rebuild, and if the block is cracked can it be sleeved on those 3 cylinders or is it junk?

I hope this is enough information for you guys to understand what I’m looking at and I look forward to any help you can offer!

Thanks in advance,
Justin
 

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cat glowing red, burning oil, no compression

SWAG: cat(s) failed, engine back sucked cat particulate
Normally, I would agree. But the cylinders that are affected by that are further back. Still, it could happen.

Sounds like an expensive repair to me.
 

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cat glowing red, burning oil, no compression

SWAG: cat(s) failed, engine back sucked cat particulate
I never understood how something could get sucked "backed" into the cylinder. If the cylinders are still pushing out and the valves are opening/closing properly, no way it could suck back. You would have a constant flow going out. The exhaust valve would be closed. I do believe the plugged cat could cause higher pressure and the valve seat breaks and falls into the cylinder. Oh well
 

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It's the configuration and the firing order.
 

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Want to get technical? Happy reading.

 

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I never understood how something could get sucked "backed" into the cylinder. If the cylinders are still pushing out and the valves are opening/closing properly, no way it could suck back. You would have a constant flow going out. The exhaust valve would be closed. I do believe the plugged cat could cause higher pressure and the valve seat breaks and falls into the cylinder. Oh well
It's called valve overlap. Intake and exhaust valves are actually both briefly open at the same time. "no way it could suck back" It's a very well known and thoroughly documented problem.
 

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"Is this thing a beast to rebuild, and if the block is cracked can it be sleeved on those 3 cylinders or is it junk?"

It's an aluminum block with cast iron cylinder liners. I watched some videos where an experienced and very meticulous mechanic using a detailed rebuild manual had it bored 20 over and installed new pistons, rings, bearings. He said it took him about 30 hours, including 5 hours to pull the engine and 5 more to put it back. Rebuild kits are around $500, which doesn't include any machining, any work on the heads. And of course you need a good rotary engine stand, and some tools (such as a good torque wrench, torque angle gage, ring compressor). Remanufactured engines with a warranty are on ebay for $2600 shipped and a $500 core charge. And you may need some exhaust manifolds or headers and catted b-pipes (review your local emissions laws). Used engines of widely varying mileage and prices are also available.

I found the youtube mechanic: Jeremy Bell. He has 13 videos entitled Titan 5.6 rebuild.

 

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Discussion Starter #9
Thanks for the replies everyone.
Best - I did find his videos yesterday and watched a few of them. He touched on some points, but I was left wishing there was a full tear down video in the mix and not starting from already going back together. I have seen used engines on ebay and have talked to a couple of local shops for reman, but I haven't looked at the reman engines on ebay. If I can find one in that price range you mentioned that'll probably be the solution. Local guys want to start at $4-6000 with a caveat (almost a guarantee according to their reviews) that you MAY need additional parts. Most reviews for those shops are complaining of charges double or tripling the initial quote with the only recourse being the option of picking up your truck with a disassembled engine in the bed.

Thanks for everyones thoughts and time. I'll let you know what we decide and find out. Either way, it sounds like manifolds should be added to the ebay cart too...
 

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It's called valve overlap. Intake and exhaust valves are actually both briefly open at the same time. "no way it could suck back" It's a very well known and thoroughly documented problem.
I been on this board for 10 years and this is the only place that talks about it. I asked my mechanic about this, said it was a myth and exhaust is only one way becasue other cylinders are stilling pushing there own exhaust out. It is a constant flow. The mechanic said the items found in a cylinder are probably parts of a valve seat. I am not a mechanic.
 

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I been on this board for 10 years and this is the only place that talks about it. I asked my mechanic about this, said it was a myth and exhaust is only one way becasue other cylinders are stilling pushing there own exhaust out. It is a constant flow. The mechanic said the items found in a cylinder are probably parts of a valve seat. I am not a mechanic.
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Hi there,
A catalytic converter can be be damaged from the engine. This usually happens if the engine has run poorly for an extended time (misfire). Example: an ignition coil that is not working will quickly ruin the catalytic converter if the engine is allowed to run more than a few minutes misfiring.
When a catalytic converter fails, the pieces that come apart can be sucked back in to the engine and cause piston ring and cylinder destruction. This happens quite often now since all newer engines have the catalytic converter so close to the engine, and engines normally pull some exhaust back in to the engine (scavenging). This allows the engine to run cleaner and cooler by burning more of the fuel mixture.

 

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Discussion Starter #13
I'm sure you guys don’t like it anymore than I do when people ask for help and never return to tell the tale.

We pulled the engine and when I removed the cats they were pristine so it wasn’t a cat failure, but since scoping the cylinder showed the walls took a beating something had to have gotten down in there. I didn’t pull the head because the yard where we got the new engine from wanted a core so I just have to guess at what. My money is on a broken piece of valve seat got down in there. That would explain the leak down results as well as why adding oil to the cylinder didn’t increase the compression.

We ended up replacing the engine is the bottom line. Thanks for all of the help!
 

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Good luck with the new engine. Thanks for the update!
 
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