Brake pedal soft update

My 2008 sprinter was leaking brake fluid requiring fill ups. There were no visual leaks anywhere. The pedal started to go down when holding at traffic lights. With engine off the pedal was hard. Engine running and applying brakes caused the pedal to drift down slowly.

Since I could find no leaks I decided to replace the MC thinking that it was leaking into the vacuum booster. Replaced the MC with one from Europarts and bled the brakes using a pressure bleeder until the calibers were flowing fluid without bubbles.

Trying the brakes without driving resulted in the same condition, a sinking pedal with engine running but hard with engine off.

Next pressurized the brake booster to 15 psi and left it like that to to see if it would hold. Amazingly it showed no reduction in pressure overnight.

Next pumped the pedal many times with the van jacked up and checked for leaks. No leaks at the calibers or brake hoses or MC. But after doing this for some time noticed some dripping from the lower part of the fuel tank and it was not diesel fuel. Turns out there is a leak in the area above the fuel tank where it is impossible to see without lowering the tank.

Called Sun Motor in Mechanicsburg PA and found out they had recently fixed a van with the same condition. The fix was to replace corroded brake tubing above the fuel tank.

This required dropping fuel tank and replacing all brake tubing in that area.

Scheduled an appointment for next week

The reason that there were no visible leak before when checking underneath I think was because the leaking fluid would disappear when driving without leaving drips when parked and when parked there were no leaks.

I will update you after the repair

There has been much discussion on here about soft brakes without obvious solutions so hopefully this will help some of you with similar problems

Today the brake line repairs were completed. As suspected the brake lines were corroded severely above the fuel tank where they can not be visually inspected and one of the lines had a leak causing loss of brake fluid and brake pedal sinking towards the floor. Tank was lowered and both brake lines to the rear brakes were replaced with copper nickel lines. Brakes are now working great again.

This issue is a safety issue that can result in a serious accident and there is no inspection possible to check for corrosion unless you lower the tank. The brake lines are steel lines and not copper nickel that is more corrosion resistant. If you drive on winter treated roads you will be more at risk for this.

The cost for the repair was $474

one of my front brake lines blew due to corrosion when I was in a 'panic' stop mode. Had to drive off the road so as not to rear end a few people-glad you found your problem (y)

My daughter has just moved to England on a two year assignment and bought a used car there. The process for inspections to get the car plated is quite involved and include inspection of the brake lines for corrosion and going forward there is what is called MOT inspections to keep the car registered

Here in Maryland and I think most states there is no inspections for this.

Different states have different inspection requirements.

From "none" (here in Washington), through "laughable" (horn beeps? headlights come on?), through "moderately extensive" (but nowhere near the UK's requirements). I think Pennsy is one of the more intrusive, but that's from foggy memory in lieu of looking it up.

--dick (ex-laughable state, now Washington)

Is a brake line rust-thru failure a NHTSA safety defect recall issue, or just a 10 year old vehicle problem ?

don't think that this can be considered a recall issue It is on the owner to inspect the brake lines for corrosion and replace as needed

NelsonSprinter said:

Is a brake line rust-thru failure a NHTSA safety defect recall issue, or just a 10 year old vehicle problem ?

Click to expand...

In the US older GM pickups are notorious for brake line rust. There complete kits sold to replace the lines. No recall so NHTSA must have given them a pass and pass it off as maintenance item.
Rumor has it the rust problem started at certain point where the vendor was changed.

Apr 8, 2015 · GM won't have to recall older trucks for brake line rust. General Motors will not have to replace brake lines on 1.8 million older pickup trucks and SUVs, some of which developed severe rust that caused the brakes to fail, the government's safety agency announced today.

https://www.freep.com/story/money/2015/04/08/general-motors-safety-brake-corroded/25460269/

Google will lead you 1000’s of posts on the problem and the available fixes.

As a side bar........I did a ground up restoration on a 1950 GMC pickup in 2014.......it appeared to have the original brake lines.

With the brake lines replaced the brakes on the Sprinter works great again. Wish I had discovered the leak earlier but the leak only happened when braking hard and after finishing driving the leaking fluid was blown off and no visible leak.