Mack double frame rust

fraser · Apr 4, 2012

I have a 99 Mack RD688S dump truck. I have had no problems with the truck but in the last couple of years started to get some rust between the frame rails. I tried cleaning the rust out and getting some paint on the frame but it has not helped. The rust is pushing the rails apart and I'm concerned about what happens next. I have been told the truck is not worth removing everything from the frame, splitting the frames apart and repairing but there is nothing wrong with the rest of the truck. Not sure what to do. Has anyone seen them run like this ?

lgammon · Apr 5, 2012

we have an 89 r model. it has rust between the frames. it has cause the outer frame to split down the bends. we welded it up and seems to be holding. it will only damage the outer frame...you still have a good one on the inside.

Soodude · Apr 5, 2012

If you have access to a pressure washer with a solution siphon tube you can get a solution for blasting rust away but I can't remember the name of the product.... I did that to our international tandem dump truck then I went and bought some rustoleum heavy rusted metal primer and sprayed the entire frame and sprayed as much into where the two frames lay on top of each other and then coated it with a black rust stop enamel. This has lasted for a year so far and no rust poking through.

Just an opinion for ya to try. I'll see if I can find a container of that solution and post it on here for ya

adam21584 · Apr 5, 2012

At work we have a 02 mach that came out of chicago I think, the frame is rust jacked bad. The frame behind the cab has already been welded and rebroke again making the truck look like it had a broken leaf spring. A frame shop repaired it again and fish plated it. Now the frame is bending right where the box bolts on the frame. I think they are looking for a new chassis for it now. I don't know if the rust has anything to do with the problems but i am sure it is not helping the situation.

TCS · Apr 6, 2012

After replacing badly rusted double frame rails on a few Macks over the decades I often wondered why the factory did not coat the mating surfaces in tar before they were bolted together like we later did when replacing them?

tuney443 · Apr 6, 2012

Use Fluid Film.It will stop the rust cold and will prevent future rusting.

bigbob · Apr 7, 2012

A freind of mine just got his truck back from Donovan equipment after having about 2/3 of the frame replaced. It was to far gone to mount a new dump body to. Looks brand new.I squirted Fluid Film between the rails on my double framed 07 international. I try not to use it when the roads are salted.

Dualie · Apr 9, 2012

I have heard of people drilling and tapping the frame rails for zerk fittings every couple feet. they will pump grease into the space between the two rails every couple of months.

But we don't get a lot of rust out here in sunny CA

Axle · Apr 9, 2012

tuney443 said:
Use Fluid Film.It will stop the rust cold and will prevent future rusting.

How often are you reapplying that it actually stopped the rust? Fluid Film is a nice product (got enough around here) but at best it slows down the process, not stop it entirely.

Alex.

2Vcon · Aug 7, 2012

Hello, I have a 84 KW 900 with the rear half double framed. Mine is swelling the inside piece and have had the outside frame crack on the underside of the bend where the AG100 attatches. I have been told that the only way to properly fix this is t unbolt everything and remove the inside frame. Sandblast the inside, paint and reassemble. Not looking forward to this. Hence I have been watching your thread closely fraser!

tuney443 · Aug 8, 2012

Axle said:
How often are you reapplying that it actually stopped the rust? Fluid Film is a nice product (got enough around here) but at best it slows down the process, not stop it entirely.

Alex.

Generally,every 4 months and it most certainly will stop rust entirely.Been using it for years to ward off rust on my snow equipment and most everything else.

NH-Eric · Jan 16, 2014

bigbob said:
A freind of mine just got his truck back from Donovan equipment after having about 2/3 of the frame replaced. It was to far gone to mount a new dump body to. Looks brand new.I squirted Fluid Film between the rails on my double framed 07 international. I try not to use it when the roads are salted.

I know its an old thread, but what was the cost of having the frame repaired? liking the fluid film, stuff seems to work awesome. Thanks

Scrub Puller · Jan 16, 2014

Yair . . . dualie

I have heard of people drilling and tapping the frame rails for zerk fittings every couple feet. they will pump grease into the space between the two rails every couple of months.

I saw grease nipples tapped into the chassis of a crane truck in Christchurch NZ . . . took a few moments to figure out what was going down.(grin)

Cheers.

Dualie · Jan 17, 2014

grease works, so far 5 seasons and not a single sign of rust. they it the rails once every couple of months right outta the grease keg. Not the cleanest solution but it works very very well .

bigbob · Jan 20, 2014

NH-Eric said:
I know its an old thread, but what was the cost of having the frame repaired? liking the fluid film, stuff seems to work awesome. Thanks

He said today it was $6800.00 Work was done last year. That is from the cab back.

NH-Eric · Jan 21, 2014

Thanks. Was that replacing both rails? Thanks again

Jaelme · Jul 8, 2015

There is a guy in nashua who repairs big truck frames. A guy i know split his mack in half right behind the cab a few years ago and it hasn't had any problems at all since he repaired it.

maddog · Jul 10, 2015

There is also a rust conversion chemical that works good, I have used it on a few different things. For my little dump truck I power washed it, scraped of any bigger chunks, let dry then sprayed this stuff on. Over 2 years and still looks good, I'll see if I can find the name of the stuff I used. Old engine oil sprayed on twice a year works also, but the enviro cops will be PO'ed.

Mike Van · Jul 14, 2015

A guy could use new oil too, rather then old crankcase stuff full of who knows what? Only a few dollars a quart when you get 5 gal buckets. My F350, single frame, but the steel actually de-laminated on it. Once that starts I don't think theres any cure other than cutting it out.

digger doug · Jul 14, 2015

I have yet to get used engine oil to stay thru a winter.

I think it's because engine oil is filled with detegents, and these
allow the water to mix with it, and get washed off.

After 25 years of fighting rust with sandblasting and various "recipes",
I now use cosmolene and Fluid Film mixed.

The FF stays wet and creeps in tight places, the cosmolene skins over in
one day or less, and doesn't attract dirt.

The cosmolene skin also seems to stand up to the blast comming off the wheels,
but as of late I have taken big truck plastic mudflaps, and attached them underneath
the body to stop the grit from hitting the underside of the cab/sheetmetal.

Mack double frame rust

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