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Discussion Starter #1
I've been having some trouble with my exhaust since the Fall. The flex portion of my exhaust rusted out so I replaced it with another flex pipe and clamped it in. I had to slip it in between the original portion of the flex pipe because otherwise the 02 sensor looks like it would have to be relocated (and require some welding for the bung which was money I didn't want to spend). So the bellow was cut out and a new one was clamped onto the existing flanges from the original flex pipe. Anyway, it started leaking again (always throwing P0420), a few times throughout this winter season (terrible potholes here likely vibrated it and the water-glass sealant loose). I was able to temporarily remedy it each time by taking a sheet of tinfoil and flattening it into about a half inch strip and wrapping it where the leak was and securing it with a worm-drive hose clamp (worked incredibly well for how simple it is).

I took my car into a garage because I have a sound coming from a wheel and enough was enough with the exhaust and I wanted a permanent fix. This is where I start running into trouble. I have to note this place was very unprofessional - when asking for a quote before getting any work done I got a response of, "Do I have to do that now?" Anyhow, first I told them I thought a wheel bearing was going - the mechanic pulls on the wheel and tells me it's a bent tie rod end so I give them the OK on that since I figure they're professionals and they would know how to solve the problem (after doing both tie rod ends in the front my actual wheel issue was never diagnosed). I also asked to have the flex portion fixed, and told them I had a flex pipe in the car but I didn't know if it could be used. As I see it, the entire section should be cut out (bellow and the flanges/nipples on each end) which is right next to some little vertical bar/hanger and would necessitate moving the O2 sensor's bung about an inch or two back. Instead they just took the flex pipe I had on hand and welded it in between the old factory welds from the stock flex pipe instead of cutting the remaining portion of the flex pipe from the exhaust piping. If that was to be considered a permanent fix they should have just left the flex pipe I had clamped on and welded it down. :rolleyes: When I get my car back not even 20 miles down the road I have a MIL for P0420 come on. Now because my wheel issue was never diagnosed and I still wanted to get it fixed and my flex pipe repair resulted in nothing other than a MIL I figured I would do my front brakes instead of them telling me there's something wrong with the front brakes making the noise in my wheel, charging me for doing a set of pads and front rotors, and then tell me something else was wrong with the wheel/suspension. While under the car doing the brakes myself, that's when I saw the terrible mess that was made. It looked like someone went crazy with a hot glue gun - blobs of weld all around and it looks charred black. I don't know much about welding but I didn't think a weld would look sooty black. Maybe they never cleaned the metal surface and it made a poor alloy of road grime and metal, or perhaps they have a gas-less welder and it just leaves nasty looking welds behind. I don't know but it looks pretty terrible. I quickly found the leak throwing the code and it was on the end of the factory weld for the pipe where I had stuck my clamped in flex pipe between (I suspect the factory weld failed from clamping the pipe so tight it cracked the weld and eventually the copious amount of water glass I applied at every seem for preventative measures chipped off when they hit it with a reciprocating saw). Worse yet, right on the other side of the leak was a cut mark from where they started to cut but quickly stopped. So they knew the right way but decided to just do a poor weld and call it good. It seems they didn't even test for leaks after working on it which suggest a serious lack of professionalism. I went there telling them the issues I had, what I thought the solution was, but when they guided me another way (doing outer tie rod ends instead of diagnosing the sound I heard for example) I accepted it under the premise they do this for a living so they're right about what they the problem is. :hand:

So after finding out that I was charged $80 for an hour of labor that was completely useless and effectively left me paying for a MIL I went back to have them take a look at it. I was there for about 5 minutes because all that was done was to clear the code and tell me that the cat's bad if it comes back and since it's been welded I'd have to replace the whole assembly. Not even another 20 miles before P0420 comes up again after leaving.

After having found the cut mark and the messy weld that looked like it had been charbroiled and being told I'd have to now get a part that's hundreds of dollars I went back and asked for the $80. I refuse to pay for a MIL - that's literally what I ended up paying for. I was told to come back in the morning the following day when the boss is in. When I get there it sounds like he knew what was up because he didn't really want to talk about it but that they'd take care of it - great I think! After waiting about 15 minutes I'm told I'll have to come back tomorrow because the cars on the lifts are going to take a while.

So I go in today and wait maybe half an hour in the waiting area and a mechanic comes in and tells me my front cat's bad because of the code. I tell him I don't think that's correct because every time it comes on I fix it by patching the leak wherever it pops up next. From my understanding P0420 could be a bad cat, exhaust leak, or bad 02 sensor. Why he was adamant it was the cat I don't know - I figure to turn me away and not return or so I come back for a $1200 replacement. I don't know why anyone would think that it was a cat after having just done work to fix an exhaust leak... Before if I wanted to replace the front pipe it would be like $400 but now it's my manifold cat that's bad and it's $750+. I'm still no better off and still out $80.

After having read through my diatribe I'm hoping someone can back my suspicion up that there's nothing wrong with the cat and it's simply the ongoing exhaust leak causing the MIL. I would graph the O2 sensors but Torque on my phone isn't launching so I can't test them unfortunately. It just seems highly unlikely and much more plausible it's an exhaust leak and not a catalytic converter gone bad. I feel at this point I don't have much of a choice but to replace the entire front pipe and its (second) cat since the pipe is pretty much dead after all the work on it. Is there any real reason to believe it could be the manifold cat gone bad? The mechanic said the pinhole leak I had wouldn't cause the MIL - but it has every other time I've dealt with the issue. I'd just hate to drop the money on a front pipe with cat only to find out the manifold cat is actually bad. Is there a diagnostic test for catalytic converters?

I think I've found the correct parts but I'd like some clarification/confirmation I'm looking at the right parts. My Elantra is an 04, with production date of 12/2003. I'm not too sure what changed between 03-04 but I think it's mostly the CVVT that shows up on some of the diagrams I've seen. I've noticed Bosal makes a curved inlet and straight inlet front pipe (I'm thinking 01-03 use straight, 04+ curved). I can tell I need the curved one through visual inspection. And as far as I can tell I have the regular federal model, but was told it was the Cal model when I was in the shop today. After doing some searching online I don't believe that at all. It appears the Cal models use a two piece front pipe - so you can bolt on a CARB approved cat. If I'm correct, I most definitely have the federal model since the cat is welded to the pipe as one piece. It's been difficult to tell from Hyundai's OEM parts diagram (went to the parts department at a dealership and they couldn't even tell me what the different front pipes were for). I think this shows the entire XD exhaust line on one diagram. It appears like I need the second one from the top of the image (curved inlet, CVVT, 030701, $557.30). Having just done some looking into what the difference between a federal and Cal model is I learned a little about engine families. Under the hood it says, 4HYXV02.0XW4. Do all XD & XD2 share the same test group? I know there was some kind of change with the CVVT so I really want to make sure I don't end up with a front pipe for the 01-03 models that fits, but won't pass emissions on my car. Is that something I need to worry about or are all federal cats on the XD series practically the same? I just worry a little because looking at the exhaust manifold cat (the one I now apparently need according to the guy who looked at it in the shop today) there's model years all over the place. My car was technically manufactured in 2003 though considered a 2004 model, but it seems the engine changed a bit between 03-04 so I'm not 100% on that. I didn't see an engine code on the block... :confused:

I found a reasonably priced aftermarket front pipe made by Walker but I just wanted a double check I'm looking at the right thing.


Why are there regular and premium converters too?

If I'm right the parts I need are 54774 front pipe, two 31534 gaskets, and probably 4 new nuts? Dry fit the gaskets from what I've read, right?

If you have any additional advice you'd like to offer about this situation please do so - I'm not just looking for confirmation but would like to understand some of the logic behind the p0420 issue and in Hyundai's part scheme. ;) If I forgot any details please let me know. Big post so hoping someone can shed some light on my predicament. Thanks! :D
 

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turbo envy
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I did not read the book you called a post...but the exhaust leak needs to be addressed. the second i replace my flex pipe section (correctly) it went away. you can pick up pipes on ebay for 75 bucks. you just simply cut the existing pipe and use the new pipe and a clamp. it works like a charm.

Future reference...nobody will read those incredibly long posts
 

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Holy god. I read the whole thing.


Your first mistake was going back to them, and getting exhaust work done at a shop that doesn't specialize in exhausts. Go to a muffler shop, tell them what you want, tell them how you want tidy welds, and nine times out of ten, they will do it.

Seriously, if you don't like the work they do, why go back to them. Unless you plan to sue them, get the hell out of there.

What does your intake manifold say? I'm pretty sure that only cali models have SULEV written on it.

The primary cat is part of the exhaust manifold on cali model XD2 elantras.
 

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'01 ELANTRA GLS
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man ive been in that situation before. my flex pipe was rusted and brittle and was leaking and kinda made the car sound cooler. it took a little while but it finally set a p0420 code. seriously what only1db said, fix all exhaust pipe problems first. next verify your o2 sensors are reading correctly. lastly go to the cat
 

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Discussion Starter #6
I just tried to patch it up with the tinfoil hose-clamp trick again. Put it right where the factory weld was I though was leaking. Still felt exhaust pressure coming out when I put my hand up to it. Turns out the weld that was just put in itself is leaking. When I turned the car on (water?) dripped out of the weld. Removed the tinfoil I had just secured and moved it an inch back to the new weld. Car is noticeably quieter - but there's still a little bit of pressure coming out. I wasn't planning on reseting the MIL and hope it goes away on its own and they I can definitely conclude it's nothing more than an exhaust leak. I think since I still feel some pressure it would be better to clear it and then see if it comes back on in 25 miles. Does anyone know the specs on a drive cycle for the XD Elantra/Hyundais?

Corrected parts list: 54774 front pipe, two 31534 gaskets, and 4 new nuts (OEM# 28679 - NUT), and 4 studs (OEM# 28532A "STUD ( 12X32 )". After making sure I have the right model can we confirm those parts? :D

I did not read the book you called a post...but the exhaust leak needs to be addressed. the second i replace my flex pipe section (correctly) it went away. you can pick up pipes on ebay for 75 bucks. you just simply cut the existing pipe and use the new pipe and a clamp. it works like a charm.

Future reference...nobody will read those incredibly long posts
I don't know what you mean by correctly - I have replaced the flex pipe section, with clamps, and it's been like that for the last 4 months. I went in to have the entire section cut out but they just unclamped the existing, stuck in the spare in the same spot, and welded it incompletely. So I ask do you mean replace just the flex pipe with clamps (done already) or take a Cal model front pipe without the cat and clamp that on up to my existing second cat? I'm not really sure because flex pipes are only about $30 at the parts store but they do carry the Cal model front pipe for around $200. I presume you mean clamp in an entire front pipe? Or did you mean pick up pipes on ebay and I read it as pick up pipes? Just $75 for a flex on eBay doesn't make a lot of sense, and entire Federal front pipe with cat even on eBay won't go for as little as $75, but just the front pipe without cat like that of the Cal model I can see going for $75.

Holy god. I read the whole thing.


Your first mistake was going back to them, and getting exhaust work done at a shop that doesn't specialize in exhausts. Go to a muffler shop, tell them what you want, tell them how you want tidy welds, and nine times out of ten, they will do it.

Seriously, if you don't like the work they do, why go back to them. Unless you plan to sue them, get the hell out of there.

What does your intake manifold say? I'm pretty sure that only cali models have SULEV written on it.

The primary cat is part of the exhaust manifold on cali model XD2 elantras.
I figured an auto garage would be able to do just as well as a muffler shop like Meineke or Monroe. I do know that there is some kind of exhaust specialist ASE certification but I figured a flex pipe would be a simple enough thing to do.

I don't see anything on the intake manifold other than YLKB on the passanger side, CII in blue on the back, and F/L Hyundai embossed on the top right with a number. No SULEV anywhere.
Here's a photo of the label under the hood (maybe has some more relevant info) as well as the embossing.



Maybe I'm looking at an older exhaust manifold diagram (linked above but shown below too) as it says 2000 (but it's got 03 parts, and 04 CVVT parts listed) and says it's compatible with 2004. It appears all the exhaust manifolds are one piece (the one on my car is in the middle of the diagram, CVVT) with cats. It does appear that the Cal model is just a pipe off of the exhaust manifold. No idea where they (Cal owners) put their primary cat on the XD model.



Thanks to those of you who had something helpful to say. ;)
 

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'01 ELANTRA GLS
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it takes 3 key cycles of failures for the code to set and MIL to come on. it might be 3 consecutive passes for it to turn off. mine did turn itself off after i got mine fixed. he meant 'correctly' fix as in cutting out the whole flex pipe section and -welding- in a new flex pipe for a complete seal, not a panzy a** clamp, i would strongly recommend a muffler shop for that option. OR most auto shops can unbolt the section containing the flex and downstream o2 (the very end part of your little diagram there) and install a whole new section of pipe.
 

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Here is what a california model 2005 XD2 GT engine bay looks like w/o the cover. It may look different than yours(cali model, CC equipped, no ABS/TC).

Excuse the dirty engine bay, this picture is like 3 years old before I started modding the car.





Just go to an exhaust shop, and get them to redo the welds I guess. It shouldn't cost more than $150 in all.
 

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Discussion Starter #9
Thanks for the info about the drive cycles, beaujohnson11. Been about 50 miles since I used a hose clamp and tinfoil "gasket" around the weld and reset the MIL so I'm going to check and see if there's something pending already. Once the emission LEDs on my scanner go from yellow to green I should be good with diagnosing it but I'd still like to graph both O2 sensors when I get a chance.

Thanks for taking the time to get a photo too, avantegt. I really appreciate it. I'm a little nervous because my exhaust manifold looks just like yours with the vertical O2 sensor and the exhaust manifold cover has the do not touch square, unlike the other cover with HOT on the diagram that specifically states federal (up to '03 though). Unlike your intake manifold mine doesn't say SULEV on top, or anywhere I can find. Just YKLB, but in the same color and font. I attached a photo because Googling it returned without any relevant results. I did just Google the WU-TWC and TWC from the emission label and I think it means "warm-up three way cat". Do you know if your Cal model has a different abbreviation string on the emissions label? Is your first cat under the exhaust manifold cover? It's just out of the photo's frame, but it's hard to see under it either way. I don't think the cat-less Cal exhaust manifold in the digram was used on XD2 models, so the diagram is just showing up to the '03 Cal model I guess. One other thing, do you know if your front pipe has a curved inlet to mate with the exhaust manifold's straight outlet? Since I can get the entire front pipe with cat for about $175 and there's a $50 rebate I think I'm going to just replace the whole thing. I put the question marks in red to make it easier to find my questions. ;)



Does anyone know what the difference between regular load and premium load catalytic converters? I think the one I was looking at was premium, so maybe the premium loads are Cal regulation level but just without the CARB stamp required in Cal. It appears from a little research even if the manufacturer has an existing cat that meets Cal emissions requirements they can't be sold in Cal until approved by CARB and stamped with it. So if there's a tier I believe it to be regular load, premium load, and CARB approved (premium load) converter. I guess if it's premium load and fits I should be golden.

On a side note, my wheel noise I mentioned in my original post could have just been because it's out of alignment and with the snow tires it really started to roar. I'm going to get some General Altimax all-seasons (had General Altimax Arctics that I loved and highly recommend but lost 3 of them this winter) on in the next few days with an alignment so hopefully that clears it up and just need to bolt on the front pipe and be done with that. Then on to some body work on the rear fenders after this brutal winter, but the weather's nicer out so it should be a fun project. :D

Thanks again, everyone!
 
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