By on November 19, 2012

TTAC Commentator jco writes:


In response to your call for more reader-submitted queries, I realized I’ve had one right in front of me and have never thought to ask my fellow TTAC commenters. I have a 2006 Toyota 4runner with the amazing 4.7L 2UZFE V8 engine, currently with 90,000 miles. I purchased the truck with 55,000 miles. However, this motor seems to have a fairly common weakness.

The thin-wall exhaust manifolds are prone to cracking at the flange where it bolts up to the head. This engine was used in a variety of Toyota
trucks, but in the 4runner, being the smallest truck of that group, this presents a particular problem. There is absolutely zero clearance between the frame and the manifold. On the bigger trucks, there are aftermarket headers available, and most will replace with those parts when/if they experience this issue.

Some owners have had success in having the dealer replace the manifolds under a TSB related to an issue with smelly exhaust, with the catalytic converters being the source of the smell. On some years of this motor, the first set of cats is the same piece as the exhaust manifold itself and gets replaced as a whole part. And there is a factory emissions warranty running 7 years/100,000 miles. So that’s usually enough to get the work done by the dealer without much complaint, as long as the symptoms can be replicated.

The noise on my truck has been there since I rolled off the lot with it. I’m not sure how much attention I paid to it at first, but it was there. The noise is far more prevalent when the engine and ambient temps are warm, and when the engine is under load. so fast/slow acceleration from start in the lower gears tends to consistently produce it. Which, truthfully, makes somewhat less sense as any crack would close as the metal expands with heat. But as with most car owners with an internet connection, I informed myself about my vehicle. And yes, I have wondered if I’m just reading about something on the internet and then self-diagnosing. But I’ve been racking up the miles, and i did purchase an extended Toyotacare warranty, so I feel like I should do my best to keep the truck properly maintained while the work is covered.

So, after living with the truck for a year and recognizing that it wasn’t just my internet-colored imagination, I took the truck in. They did actually recognize the exhaust smell, but only replaced ONE of the 4 catalytic converters. and it was not one of the ‘pre-cats’ directly off the manifolds. As for my noise complaint, they determined that they were hearing something, and that it was caused by the exhaust system, which had been installed at some point by a previous owner. it consisted of some cheap piping and a Flowmaster muffler (which, let me tell you, sounded AWESOME with the V8, heh), and looked to have been done on the cheap by a muffler shop. They found some leaking at the seams, and would not attempt to further diagnose the noise issue without a full OEM replacement. a $1,000 assembly of parts not covered because it is considered a ‘wear item’. they sort of relented and agreed to install an aftermarket bolt-in part at a quarter of the cost. after all that was done, they determined the noise was ‘normal’ and sent me on my way. and it still sounds exactly the same. that was at about 80,000 miles, about 6 months ago (haha I drive a lot).

With my driving habits, and edging closer to the warranty expiration, I took it back in yesterday. Though it was a cold day, they were able to hear the noise, again. and again they stated that it was ‘normal for this engine’. The reason I am leaning towards the manifold and not a ‘tappet’, or ‘valvetrain’ noise as the service manager claimed, is just the nature of the sound. were it a top-end noise, the amplitude would be higher. same with a downstream exhaust leak. what i hear is a ‘tick’ with what sounds like every pulse from ONE cylinder. meaning at around 1500rpm under load, it will repeat itself approximately once per half-second (i’m guessing, but that seems close). and i would describe valvetrain noise as more of a constant clatter anyways, prevalent under any operating condition.

So what should I do? Take it to another dealer? Take it to an independent guy for at least a casual diagnosis? Is there another cause for this issue? I’d love to say this is just a normal noise, but I know it isn’t. Having done my research, the only way to actually SEE a crack in the common location is removal of the manifold. not a job I am equipped to handle. I truthfully don’t mind the noise so much, but I love this truck and because it’s a Toyota
truck, I plan to put at the very least another 100,000 miles on it. and so I don’t want the problem to further degrade and fail over time, given the expense and difficulty of replacing this particular part.

Sajeev Answers:

I love how you “love this truck and because its a Toyota I plan to put at the very least another 100,000 miles on it.”  Not because I’m a hater, because I plan on doing the same thing with my orphan Lincoln-Mercury vehicles.  We all have our quirks, some of us are just crazier than others: and both of us should just give up and find something else to drive.

Or not. Because odds are the replacement manifold is an improved design, if this is any indication.

Having personally dealt with bad exhaust manifold gaskets, leaky headers and the like, it does sound like your diagnosis is on the money. But who cares?

Replace it when it gets worse.  I’d recommend cutting off the replacement mufflers you put on after the dealership demanded it, replacing with some mild flowbastards (get it?) or Magnaflows, or whatever floats your boat.  I like the mufflers from the 2005-present Mustang GT: you can get them for free at some exhaust shops when your average stangbanger demands a more obnoxious sound…but they are actually the best balance of rumble and sophistication on the market!

Those of us who like to wrench around on older vehicles simply gotta love free shit. Especially when it masks the impending failure of your cracked manifold. Let the problem get worse, obviously worse, then let an independent mechanic fix it.

Bonus!  A Piston Slap Nugget of Wisdom:

As you modify a vehicle after the warranty expires, avoid the dealership’s service department.  It’s in both parties’ best interest to keep it like that: less BS for the owner and less risk of giving bad service (at a lower profit compared to other tasks) with the repercussions that come with.

Take it from the guy farting around with a restomod Mercury Cougar for the past 13 years. Time to cut the cord.

EDIT: I forgot that there was still an extended warranty on the vehicle, that changes everything.  Going to another dealership and asking them to scope it out (literally) for a crack is a good idea. 

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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10 Comments on “Piston Slap: Exhausted after a little Crack?...”

  • avatar

    I think the issue is that he’s still got an extended warranty on the vehicle that would likely cover the manifold repair. In which case, if it IS the source of the noise, he would want to have it repaired under his service contract instead of shelling out later.

    I’m not sure what the technicians at the dealer already did to attempt to track down the noise, but there are a couple things that can be can do to track it down and get this resolved for your own sake.

    A mechanic’s stethoscope is a fairly cheap tool investment and a basic starting point in tracking down the source of the noise. Your local parts store, harbor freight etc. will have this.

    If the noise really is valvetrain related, it will be loudest around the cylinder head and front cover areas with the stethoscope.

    If it is loudest on the manifold at a particular runner, this would likely confirm the cracked manifold theory which you could ask your dealer to confirm. The dealer would likely have a more sophisticaed Engine Ear electronic tool which could be used to confirm the source of the noise as well.

    Since it sounds like the current dealer has all but written off the noise as normal, you may want to take it to another dealer that will honor your manufacturer service contract to get a fresh perspective.

    Keep in mind that the noise MIGHT actually be normal since it was stated the noise was present when the vehicle was purchased. If one of these dealers has another 4Runner with the same engine on the lot, ask them to compare the noise to that vehicle to verify if it is indeed normal.

    If it is not a normal noise, be persistent and get the most out of your service contract.

  • avatar

    If you uh, exhaust your resources at the dealership, you can still take it to an independent repair shop where they can still source OEM parts from the dealer and install the updated manifold if one exists.

    Since it isn’t a cast design, it could possibly be welded, but you’d have to be an extremely competent welder. That and you’d have to pull it to weld it, an all day job for sure.

    Pic of said crack:

  • avatar

    According to the EPA regs, major emission components are warrantied for 8/80,000 on post 95 cars and light trucks.

    Perhaps Toyo added 20K miles, but they can’t cut a year off.

    Beyond that, the described symptomology could point as much toward a failing manifold gasket as a manifold issue. Regardless, no dealer is going to sell their regional on approving work for some minor ticking noise for a 90K car that isn’t being driven by the original buyer. Sad to be having any problems on a 100K Toyo, but now is the time for the poster to either learn some basic exhaust stuff, or whip out the wallet.

  • avatar

    A cracked or bad manifold is a walk in the park compared to the rotted and cracking frame that needed replacing on my friends 05 Toyota truck. Consider yourself lucky. Drive until it fails and replace.

  • avatar

    Hey, I put a set of 2005-2010 Mustang take-off mufflers on my ’96 GT to replace some rotted out Flowmasters a couple of years ago. They sound fantastic and I figured that a pair of practically new, high quality OEM stainless steel mufflers that should last forever for less than what a single el cheapo aluminized muffler that will rust out in a few years was going to be hard to beat.

    They will most likely need some modification as they have a turn up to go over the axle on the inlet and a clamp for the tips on the outlet which may or may not work for your application – trivial for a muffler shop to cut off and weld on appropriate fittings, not as trivial for a hack welder trying to weld stainless in his garage, but also not impossible.

  • avatar

    since I sent this in a few months back, I have an answer, sort of. my mistake seems to have been my loyalty to my original dealership. i had returned it to that location on at least 3 occasions for that problem. that location is about 25 miles away, and there are probably another 4 or 5 toyota stores closer to me than that. i decided that i’d had enough and drove over to my closest dealer location. drove into the service bay, talked to a service writer who listened to my complaint and said he’d check it out. he then got in the truck to check the mileage and had to start it up to allow other cars to come in behind me in line. as soon as he started it up, he heard the noise.

    so he said “yeah, that’s an exhaust leak”. he gave it to a tech and had him put it up on the lift while he consulted with Toyota corporate about the repair. an hour later, he sent me home, told me to come back in 2 days when the parts come in and that i’d have a loaner available for the duration of the work. they actually had the truck back to me less than 24 hours later (a shame since I was really enjoying the brand new Camry loaner). it was a pleasant dealer experience and i’ve since returned to them to have additional work done, under warranty, without having to complain to them about an obvious problem.

    I knew I wasn’t wrong about the noise. an exhaust leak is kind of an obvious noise and once you hear it, it’s fairly obvious.

    and i would have no complaints about waiting for the part to fail, as it isn’t something that would have left me stranded. but with nothing aftermarket available, and the complexity of the job on this specific vehicle.. well i wasn’t going to just give up if there was a warranty i knew i’d be able to take advantage of.

    my concern now is that the other side is going to eventually fail, and i just crossed over the 100k mark about a month ago. the other manifold will probably fail over time, so i guess i’ll just have to take care of it at that point. oh and that part link you posted in your response won’t fit this truck, since the 2005+ 2UZFE is an updated design, with lots of revisions and the new manifolds are 2 piece and include the primary cats.

    the exhaust system they forced me to replace (I should have just said no to that ridiculous request) was an aftermarket cat-back system that has actually been a decent replacement. although i miss the noise of the flowmaster, as this system is actually quieter. there isn’t space for a muffler after the axle, so the muffler sits inside the frame and the rest of tailpipe goes up and over the axle to exit out the back.

    so be persistent, i guess, is the lesson. oh and don’t deal with a dealership who doesn’t want to perform warranty work.

    • 0 avatar

      jco, do you live in the rust belt? I live in SC and our 2003 V8 4Runner has 140k on it and so far no manifold issues. Just wondering if this is something that inflicts all or just rust belt vehicles.
      For a stock exhaust ours has a nice burble at idle.

      • 0 avatar

        yeah, although the truck has seemingly always been well-maintained. it has been garaged for the duration of my time with it, and judging from the paint it looks it was before that too. but that leak was there at 55,000 miles when I got it, so that’s what was interesting to me.

        my friend in south carolina also has a 2004 V8 4runner with like 180k, but i do think his might be affected..

  • avatar

    The person considering buying his wife a Lexus GX 470 might want to read this post…

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