Exhaust system issues and modifications

racertracer · **Posted:** Mon Dec 21, 2009 5:35 am

My exhaust system seems to be making a clanking rattling sound coming from the engine compartment area, which sounds like a loose piece of metal tapping on metal. Not sure where it's coming from and if anyone has any ideas, I would appreciate the help.

I am considering modifying my exhaust to a 2 1/2" cat back system to hopefully clear up the issue and improve performance.

I would be interested to learn from members that have performed an exhaust modification if performance has improved?
Has your mileage per gallon increased?
Did it alleviate any rattling noises?
What type of muffler (if any) and tail pipe kit did you use?
Was the cat removed?
Would you have done it differently?

From a newbie trying to make his vehicle better.

Thank you in advance

dgeist · **Posted:** Mon Dec 21, 2009 2:30 pm

racertracer wrote:

My exhaust system seems to be making a clanking rattling sound which is coming from the engine compartment area, like a loose piece tapping on metal. Not sure where it's coming from.

I am considering modifying my exhaust to a 2 1/2" cat back system to hopefully clear up the issue and improve performance.

I would be interested to learn from members that have performed an exhaust modification if performance has improved?
Has your mileage per gallon increased?
Did it alleviate any rattling noises?
What type muffler (if any) and tail pipe kit was used?
Was the cat removed?
Would you have done it differently?

From a newbie trying to make this vehicle better.

Thank you in advance

I replaced from the flange after the Cat to the up-bend just before the rear axle with 2.5" pipe, bent slightly in 2 places to match the path of the stock muffler that it replaced.

- Slightly more MPG
- Slightly more low-eng growl to the exhaust note (stopped noticing after about a week)
- More clearance underneath
- Less delay on turbo spool
- Regrets: Didn't find a more talented welder to do the work. It looks like toothpaste squeezed on the pipes...
- No Cat removal. That would be the part that makes it illegal. Everything else is just user preferences. Not judging, just saying....

stoutdog · **Posted:** Mon Dec 21, 2009 4:06 pm

IMO, don't waste your money on the catback system, unless you absolutely must have shiny exhaust piping underneath your CRD. If you want to do something to the exhaust, you should either 1) replace the muffler with a piece of 2.5" pipe or 2) replace the muffler with a Magnaflow (part #12226). The Magnaflow + install should cost < $100.

Whatever you do, make sure you remove the downsizing flange between the cat and the muffler.

Benefits: slightly better mpg, better coasting ability (improved mpg depends mainly on if you can take advantage of the improved coasting). The CRD will sound a little meaner, but no louder.

Others will disagree, but I recommend leaving the cat alone. It is very effective in cleaning your exhaust, substitutes for a muffler, and gutting it will give you very little if any performance gain.

warp2diesel · **Posted:** Mon Dec 21, 2009 5:53 pm

stoutdog wrote:

IMO, don't waste your money on the catback system, unless you absolutely must have shiny exhaust piping underneath your CRD. If you want to do something to the exhaust, you should either 1) replace the muffler with a piece of 2.5" pipe or 2) replace the muffler with a Magnaflow (part #12226). The Magnaflow + install should cost < $100.

Whatever you do, make sure you remove the downsizing flange between the cat and the muffler.

Benefits: slightly better mpg, better coasting ability (improved mpg depends mainly on if you can take advantage of the improved coasting). The CRD will sound a little meaner, but no louder.

Others will disagree, but I recommend leaving the cat alone. It is very effective in cleaning your exhaust, substitutes for a muffler, and gutting it will give you very little if any performance gain.

I hung on a back pressure gauge and found out that the only time I had any back pressure with the cat after the mod mentioned by stoutdog was after a lot of stop and go driving. Accelerating up the entrance ramp to an expressway cleaned out the cat in seconds. THe cat is big enough, but the flange behind the cat is restrictive. X2 on the mod.

Glend · **Posted:** Mon Dec 21, 2009 6:28 pm

Agree with the two above. I have just installed a Magnaflow & full 2 1/2" pipe out of the Cat (ditch all that restrictive flange and pipe). IMHO to get best results out of this mod you also need to open up the intake side of the engine - through either an induction pipe or ram air snorkel (like Airlflow). A diesel that breathes better performs better. Very happy with the results.

CRD Joe · **Posted:** Mon Dec 21, 2009 8:56 pm

Ive got a cat back 2.5" with no muffler. I love the way it sounds. Im not 100% sure but I think Ive lost a little
back pressure... :CAMPING:

linewarbr · **Posted:** Tue Dec 22, 2009 1:59 pm

I installed the Magnaflow catback system (muffler + tailpipe, direct bolt-on replacement w/ no welding) for the Libby. Got it from a dealer with an Ebay store for $350, so I snapped it up. Left the cat alone.

Throatier exhaust note, quicker turbo spool-up are the immediate benefits. I got the GDE tune at the same time so I don't know what mpg gain it may have given me.

CATCRD · **Posted:** Tue Dec 22, 2009 4:33 pm

It's probably not your exhaust. It's your passenger's side engine mount.

racertracer · **Posted:** Tue Dec 22, 2009 7:38 pm

linewarbr, could you tell me what model number exhaust and tail pipe you used?

I am considering going with a magnaflow just not sure which is the better one.

Must the rear tail pipes be replaced also and if so what is the manufacturers name and part numbers.

Both engine mounts were replaced, alternator decoupler replaced, pulleys replaced.

Also there is still a light squeal coming from the serpentine belt below the water pump , it's not the same loud tinny clancking noise that is coming from the exhaust manifold, turbo charger area.

Any ideas.

These noises are driving me nuts.

RTStabler51 · **Posted:** Tue Dec 22, 2009 8:42 pm

I have the MBRP exhaust, and didn't notice any difference except for sound.

grommet1 · **Posted:** Sat Dec 26, 2009 8:43 pm

I agree with CATCRD, it is probably a broken engine mount making the rattling noise, I had my passenger side replaced <30k miles.
One of the very first things I did to my 06 was remove the muffler and install a 2.5" pipe in its place after the cat; Meineke did it for about $60. It improved the performance, especially when combined with ORM. My mileage also increased almost 2 mpg. It is noticeably louder until you reach highway speeds, but sounds pretty good actually. I would highly recommend deleting the muffler.

racertracer · **Posted:** Sun Dec 27, 2009 7:22 pm

Well, I discovered that the rattle was coming from the transmission area and the protective skid plate directly under the engine.

First - The transmission had been overfilled by the transmission shop that installed the new Euro TC and pump by 1 1/2 Qt over the fluid level which created a shake and constant ticking noise.

Second - The skid plate had a stripped bolt that prevented the plate from being secured to the frame creating a loud rattle. It runs smoother with hardly any noise now.

I am still considering the cat back exhaust modification.

NJCRD · **Posted:** Thu Dec 31, 2009 10:39 am

I straight piped mine. Diesels don't need back pressure. You will notice a healthy diesel tractor sound as well as a quicker boost from the turbo. I really can't tell the diff in mpg as it's been off the truck for so long. For what it's worth, straight pipe it and if you don't like it you can always purchase a muffler.

linewarbr · **Posted:** Thu Dec 31, 2009 2:53 pm

racertracer wrote:

linewarbr, could you tell me what model number exhaust and tail pipe you used?

I am considering going with a magnaflow just not sure which is the better one.

Must the rear tail pipes be replaced also and if so what is the manufacturers name and part numbers.

Sorry to be so late in replying, I hadn't checked this thread in a while.

The p/n for the Liberty full catback exhaust is 15870. It comes with muffler and tailpipe, so it relpaces everything from the cat flange back. Includes a 3" chrome tip. You can do the removal/install in your driveway or garage if you can jack up the starboard (passenger, in US) side rear to allow enough play to pull the old exhaust down and forward.

I ordered mine from WideOpenSpeed's eBay store. If you decide to go with the catback, PM me on how to get it at a good price.

Cowpie1 · **Posted:** Mon Jan 04, 2010 9:33 pm

Or... you could just remove the cat and go 2.5 pipe all the way using only a magnaflow for some sound deadening. Doing this isn't a problem where I live. No emissions checks in Iowa and no one would know anyway that a Cat came on the CRD anyway without looking it up. Oh, did I mention that the EPA sticker in th engine compartment just happened to come off? Oh well.

The flange and clamp that connects to the turbo can vibrate loose also. Check that it is tight. I haven't had that happen to my CRD, but it happens every once in a while with the other diesels I own.

geordi · **Posted:** Tue Jan 05, 2010 1:05 pm

The only cats involved with my CRD ride inside and have a taste for fresh tuna. I put a Flowmaster muffler on just to hold down the racket a little, but the 2.5" pipe from the turbo-back is a nice free-flowing way to get the bad stuff out.

As far as back pressure being helpful... That is a myth, for gassers too. Exhaust is bad. You want it out of the engine, so that fresh air can enter on the next rotation.

Perfect example: I have an RV with the 454 Chevy big-block. This monster inhales a HUGE amount of air, and when I was reworking the exhaust b/c it had rotted from age, I was told the same nonsense about needing back pressure. The argument was that pressure in the exhaust pipe "helped the next cylinder to extract all it's exhaust gasses too" and that if I didn't have both an H-pipe AND a restriction, the mileage would drop.

On a 6-ton RV with already 6mpg performance? Hmm... That doesn't compute. I replaced the single 2.5 inch pipe system (yea, get that!) with fully-separate 3 inch pipes and jumbo truck mufflers on both sides. There is NO connection between the engine banks, and the size of the collectors on the headers is the same diameter as the rest of the long pipe. Back pressure? Not in my engine!

End result: The mileage did change b/c of this. From 6mpg to 8mpg. The engine also is MUCH quieter, and now can be left to idle for more than 5 minutes without worrying about overheating.

racertracer · **Posted:** Mon Jan 11, 2010 7:02 pm

Update.

I had the local Midas shop remove and replace the muffler with a magnaflow #12226 2.5" and I must say that I went from 21.2 mpg to an inprovement of 23.8 mpg in town. The noise and rattle I was hearing from the muffler area is gone and engine noise and wabble is reduced.

If I knew the noise would have been reduced this much, I would have had the muffler replaced from the start.

This little beast Flys, it's incredible and I am loving it.

Muffler purchased from Amazon.com - $66.00 delivered.

Installation - $75.00

P.S. The 2 1/4" existing muffler flange does not require to be enlarged to 2 1/2". The existing muffler is the culprit and it is where the flow restriction occurs.

stoutdog · **Posted:** Mon Jan 11, 2010 8:51 pm

Good choice of mufflers.... Most of your mpg gain is going to be realized by taking advantage of your engine's new coasting ability. GDE + Flow-Thru muffler = ability to coast for ridiculously long distances. I've gotten into the habit of removing my foot completely off the throttle when I'm ~100 yards from a red light.

If I'm doing 45 at the time, I might be doing 35 when I reach the light. :BANANA:

geordi · **Posted:** Tue Jan 12, 2010 12:11 am

Pshh, I'll go you one better

Not only will I start coasting as soon as I see a light change in front of me (sometimes as much as 1000 feet) but here in Virginia, I'm coasting down every single hill. Gotta love it!

Right now, I think it is the only thing keeping my mileage at anything decent. I'm waiting for the boost solenoid to arrive, but typically I can fill the tank right to the top of the neck, and it will go just about 100 miles before the needle moves off of full.

This last tank I noticed it... I've gone just about 100 miles now since filling up... And the needle is below 3/4, heading toward 5/8. YUCK. :furious:

I've also noticed recently that my EGT has been almost glued to 1000 degrees when I'm doing 65/70mph steady, where before just a couple weeks ago it was around 700. I also recall a couple months back, that when not towing, at the same speeds the EGT was at 600.

So something is definitely getting worse. I'm pretty certain that it isn't the solenoid not functioning, but it isn't able to make a good seal and is letting the vacuum escape, so the turbo can't hold high boost.

At least thats what I hope is the situation. If not... I'm out of ideas, and it isn't tossing any codes. (of course)

stoutdog · **Posted:** Tue Jan 12, 2010 1:33 am

geordi wrote:

Pshh, I'll go you one better

Not only will I start coasting as soon as I see a light change in front of me (sometimes as much as 1000 feet) but here in Virginia, I'm coasting down every single hill. Gotta love it!

Right now, I think it is the only thing keeping my mileage at anything decent. I'm waiting for the boost solenoid to arrive, but typically I can fill the tank right to the top of the neck, and it will go just about 100 miles before the needle moves off of full.

This last tank I noticed it... I've gone just about 100 miles now since filling up... And the needle is below 3/4, heading toward 5/8. YUCK. :furious:

I've also noticed recently that my EGT has been almost glued to 1000 degrees when I'm doing 65/70mph steady, where before just a couple weeks ago it was around 700. I also recall a couple months back, that when not towing, at the same speeds the EGT was at 600.

So something is definitely getting worse. I'm pretty certain that it isn't the solenoid not functioning, but it isn't able to make a good seal and is letting the vacuum escape, so the turbo can't hold high boost.

At least thats what I hope is the situation. If not... I'm out of ideas, and it isn't tossing any codes. (of course)

Yea, I used to be able to go 100-120 miles before the fuel gauge moved... with the latest GDE tune, the gauge is now linear (1/4 gauge = ~5 gallons). I routinely drive up to Flagstaff, which is a 6,000ft. elevation gain from the Valley. On the way back, there are three sections where I can coast for ~5 minutes... no pedal, no brake. It's fantastic.

I can coast just as far, I would venture to guess... I'm just careful about whether or not someone is behind me. If it's an open road back there, I coast as soon as the light turns red

Exhaust system issues and modifications

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