linetrash75

hey my exhaust manifold cracked i was wondering if any body had a good one laying around ? I was also wandering if that would play a part inthe crampy mileage i have been getting 14-15 since i bought in april i mostly drive freeway speed 70-75 and very little town driving or idle time. A 98, 5spd, 3.54 3500, quad cab no mods that i know of, 150000 miles

smittybuilt

don't know if it has anything to do with mileage, but you can just weld the crack up. cheap solution. if you decide not to weld it up let me know i might be interested in buying it for a backup.

gsdog1

Weld it or go with an ATS 3 piece manifold. Not all that expensive really.

Matt

linetrash75

thanks guys i didm't know if welding was the way to go or not. any ideas on the mileage runs great but the best tank i've seen was barely 16 ive done fuel and air filters, idont know what next i had a 92 and a 90 they both got 18-19 withthe pump turn up about 10% and staight pipes. they seemed faster too. i read on thread last night guys talked about soot on 1/4 panel like it wasn'
t suspose to be there mines been that way since i bought it. any info would be great.

jed

RATTLINRAM

You might try checking out the IAT sensor as it can cause low fuel mileage problems if dirty. CHECK THIS OUT

linetrash75

thanks i'll give that atry later today wifes got the truck now i hope it helps

jed

Rauschbo

Contact Merrick Cummins on this forum - he hooked me up with an ATS 3-piece ($400-ish) which does not have the same design flaw as the OEM; OEM locally was $540-ish with gaskets, and would face the same risk of cracking as the original.....

I don't think you can weld the cast iron piece very well...

Installation was a bit over three hours....very straightforward, no special tools or skills required.

I could only see a ~1" crack on the top - when I got it off, I found that the crack extended COMPLETELY around the underside. My mileage had been falling off from ~19-ish to under 16 (could be the colder weather, not sure what the primary contributor was)

linetrash75

raushbo, thanks think i'll try welding first know a guy can weld anthing but the crack of dawn, going to adjust the valves today after church hopefully help

Monty

If a crack was big enough. I would think that mileage would suffer since the exhaust is what actually drives the turbo. Which would lead to loss of exhaust volume, pressure etc. that drives the turbine wheel.

1BadDzl

That was my comment totally. If you have a cracked exhaust manifold you loose exhaust gas pressure to the turbo which results in less boost-less fueling-low power and lower fuel mileage. You will not believe the difference between the ATS exhaust manifold and stock. Spent the $ and get the ATS. Don't weld the cracked manifold. No matter how good the welder it will recrack on either side of the weld. There are some tricks to installing the ATS manifold-figure about 3 hours for the install.

linetrash75

figured if i welded it, id have some time to get the $$ for the ats manifold or time to find a used one anyhow. kind of figured loss of exhuast pressure have trickle down effect. another ? still have what i beleive is factory exhuast, but i think somebody took it off maybe put it on backwards? comes off turbo 3" to muffler, 4"out of muffler to resnate or maybe cat? 3" the rest of the way out. the reason i'm wondering read a thread earlier guy said his was 3" off turbo to cat, 4" between cat and muffler, 3" out of muffler. any ideas?

jed

Rauschbo

....could be a temporary "band-aid", but as someone mentioned, it will crack next to the weld (Heat Affected Zone issues / Carbon Leeching, etc.); Seems like a pain to have to R&R the thing twice!

smittybuilt

i've seen several welded with no more cracks, but they had a very good pipe welder do the welding, but they could crack at any time.

Monty

Working at Freightliner, I see alot of these come in from cracking. And the number 1 engine that I have seen crack more 3 piece manifolds is the ISB. Closely followed by the 3126 CAT and the Series 60. The only thing these three have in common is the 3 piece designed manifold and a single head which I feel is the problem.

y-knot

First I don't like the ideal of the welded manifold, I feel it is temporary at best, and I would avoid it.
Also I would think that the prime time for a exhaust manifold to crack would be in very cold weather. One were the manifold is very cold, and the truck is started and not allowed to warm up slowly. And the other would be in very cold weather ware the manifold (truck) is used in short runs, sits for not ling and another short run, like a delivery deal. The constant cycling of expansion and contraction, might develop a crack.Good luck.