GM truck and SUV rusty brake lines

Just because GM got out of recalling '99 to '09 trucks and SUV’s because of rusty brake lines doesn’t mean this still isn’t a big problem. Last week I was forced to do an ABS stop in my '04 GM SUV to avoid an idiot. After the event I noticed a “service brake system” warning on the dash. When I tried the brakes, I had a very long pedal and nearly no brakes at all. I guessed a burst brake line and could see brake fluid dripping from below the driver’s seat area where the ABS unit is mounted. I limped the truck home losing more and more brake capability as I went. The parking brake has never worked on the truck so it was not an option to stop the truck.

Upon inspection, I found that the 2 master cylinder feed pipes and the 3 wheel pipes from the ABS unit were all very rusty and brake fluid was dripping from the area. One or more of the lines had burst. Since I had virtually NO brakes, I’d guess I lost more than one. The lines looked good at the exposed ends but were compete trash between the framerail and the floorboards. I’ve stripped all 5 hardlines off the truck and I’m waiting for delivery of a replacement hardline kit (about $65 complete). It is a pain to replace but you don’t need a lift, just a jack and a couple of jackstands.

If you or any family or friends drive one of these trucks, please have them checked. If there is anything more than surface rust, replace them.

That’s pretty cheap for all those brake lines. I hope you marked where they all go while you’re waiting for the new ones. Would it help to drill some drain holes for the hidden areas to get the salt water out?

At 15 years old it is not surprising that the lines are getting bad, especially if you live in the states where a lot of salt is used in the winter.
GM, in my opinion is not the culprit, but the use of road salt. I see this on most makes and models of cares and trucks.

Still $65 is pretty cheap.


I have to agree with @Yosemite All cars and trucks are susceptible to brake line rust through regardless of brand.

@Bing There are no drain holes to drill. They are all exposed to the underside of the truck. I’ve only had this issue on one other vehicle, a 12 year old GM sedan and that one was right at a clamp. This was all along the lines above the frame rails behind the splash panel. The line to the rear wasn’t too bad behind the side-saddle gas tank but above the tank they are a mess. Yup, I have diagrams to get it all back together.

Yeah, $65 is very cheap. I was happy about THAT! I wouldn’t even consider bending my own for that price. I saw stainless lines on EBay for $175. Since I no longer live in a snow state, I should get more than another 11 years with zinc plated lines.

@Mustangman, were the old ones galvanized too, or just carbon steel?

Like @Mustangman, I find them rusted worse where the hold down clamps are located. I think the clamp allows more slush to hang on that spot and constantly drip the salty brine for days if not weeks. And it seems that once you touch them to work on some other part, you inadvertently cause the leaks.


@jtsanders The old ones were galvanized (or zinc dipped). I think that is a minimum spec required by NHTSA. Maybe these are a bit shy a little zinc.

I think the new ones are supposed to be nylon coated as well. That’s what the description said. They are supposed to be delivered today.

The hold-downs are all plastic and corrosion, for this truck, weren’t limited to those spots. It seemed worse anyplace they traveled between the frame and body. The parts just hanging out in space look great. Maybe salty snow packed between frame and body during winter making it a perfect spot for corrosion.

The wife’s unit-body car is older and has no issues with the brake lines at all. No real place to trap snow, either.

Was this truck seldom used?
I have numerous experiences with seldom used cars/trucks that rusted out brake lines, pans, subframes etc in record time compared to those that were used daily. Especially when exposed to winter conditions and de-icing of roads…

Sounds like the “idiot” helped tip you off to real safety hazard in your vehicle.

Do you live where they do not do yearly safety inspections?

Its odd that this occurs on trucks and not cars. It seems like the manufacturer would use the same vendors for parts like these. Adding the nylon coating makes me think that the zinc coating came off over time, maybe due to road debris. Still, it’s odd that it would be just GM trucks and not cars or other manufacturers products. It seems likely that the tubing supplier provides similar parts to other aut companies. @Mustangman, do you know from your career whether it was a captive source or not?

@TwinTurbo not a seldom used truck for the first 9 years at least. Pretty much my DD, with regular trips to the drive-thru automatic wash with under-car spray. I’ve tried to prevent this dumb stuff at breaks in the winter weather. Forums for Avalanche enthusiasts and GM truck sites have loads of people complaining about this.

@andrewRA the idiot did me a bit of a favor, I’ll admit. I’d hate to have this happen with a trailer attached. Neither my former wintery state nor my now “never snows” state does safety inspections. I do. I just missed how bad these were because the worst rust was well hidden. If I can miss it, others can, too.

@jtsanders I don’t think the supplier was a captive one. None of the Delphi divisions made brake hard lines, hoses, yes, and 3 of my 5 hoses failed before 60K miles so all are replaced. My wife’s Saab (Euro GM) has nylon coated brake pipes (like the new ones that just arrived!) I think the difference might be the frame. The car has no place to trap snow and ice like the truck does. Above the frame and below the body is where the worst rust was. The car has the nylon coated lines and the snow doesn’t pack in. I’d say both contribute to longer life.

Rust can occur in strange ways. My Passat once had front brakes replaced, not because of pad wear, but because the rotors were rusted through. The Mechanic said he could see through them in places. 120k miles

The pads were replaced at 70k. My guess is that I use the brakes infrequently (I’m a very conservative driver), live in a salt zone, and the car often sits for 5 days unused. So the rotors could rust through.


I had the same problem with my 2001 Silverado. Soon after replacing the brakes lines, the gas lines rusted and leaked just under the engine - again where holding clips held the gas lines in position. When I had the gas lines fixed, I ordered all new gas lines from Rock auto that were already bent to shape. The mechanic said that as he touched the other gas lines they started to leak too, so replacing them all was the best thing to do.

Good to know @psanzone! So far, from what I can see, my fuel lines look OK (but that’s what I thought about the brake lines, too!) I need get out the lights and mirrors to get a good look above the fuel tank. Its about time for a new fuel pump. Maybe do both at the same time. If I plan it right I can get the tank empty before I change the pump. They usually fail right after I’ve filled up.

I still think that here in the north…where the lines follow the frame, there are just so many places where large caked on, accumulations of slush, have so many edges to stick to. Under the hood it’s a bit warmer and the lines are more out in the open and able to shed that slush much easier.
Driving through the slush and wet snow, the front tires throw all that up right around the frame rails and it sticks to the brake lines, fuel lines, E-brake cable, holes in the frame, tranny support cross member, wire harness, dead cats, etc, etc.