Surge Brake Solenoid

barthel

barthel

Petty Officer 3rd Class
Joined
Mar 20, 2012
Messages
94
Evening all,

I have been trying to bleed the surge brakes on my trailer. Long story short, the master cylinder was a ball of rust and completely shot. Pulled it off to replace it. When I had it off, I blew air through all lines to clear them of any debris.

Got the system back together and tried to pressure bleed it, no dice. I traced it back to the quick connect, then pulled that out. I'm still not getting fluid or pressure past the reversing solenoid.

Is there any way to check that it's bad, blocked or can it even be unblocked? Or am I pretty much resigned to replacing that too.?

TIA
 
J

jm625

Cadet
Joined
Aug 15, 2012
Messages
6
Re: Surge Brake Solenoid

In order to check if it is even functional, turn key on at towing vehicle and shift into reverse, assuming you have power to the solenoid with vehicle in reverse, there should be an audible click. if not it is likely defective anyway, and should be replaced.
 
barthel

barthel

Petty Officer 3rd Class
Joined
Mar 20, 2012
Messages
94
Re: Surge Brake Solenoid

Wouldn't it still allow the fluid through if not energized?

I don't know if it's full of crud (from the master cylinder) or failed closed.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,538
Re: Surge Brake Solenoid

it should be open when not energized. sounds like you also need a new solenoid.
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Surge Brake Solenoid

Scott Danforth said:
it should be open when not energized. sounds like you also need a new solenoid.
Click to expand...

There are two types of solenoids.

One type is normally open and closes when energized to block flow to the brakes.
The other type is normally closed and opens when energized to dump the brake pressure back to the reservoir.

They are matched to the Actuators.
Did you replace the actuator with the same style?
 
barthel

barthel

Petty Officer 3rd Class
Joined
Mar 20, 2012
Messages
94
Re: Surge Brake Solenoid

Not sure what the "actuator" is. I replaced the the master cylinder. I re-used the pushrod (it's part of the trailer) and the solenoid. I'm 99.9% positive it's normally open, it has the 5th wire that works off the reverse lights.

In it's natural state (in the driveway, unenergized) it doesn't seem to be letting fluid through. I just wasn't sure if they could be cleaned out, blown out or if my only recourse was to replace.
 
04fxdwgi

04fxdwgi

Senior Chief Petty Officer
Joined
Jun 10, 2011
Messages
754
Re: Surge Brake Solenoid

barthel said:
Not sure what the "actuator" is. I replaced the the master cylinder. I re-used the pushrod (it's part of the trailer) and the solenoid. I'm 99.9% positive it's normally open, it has the 5th wire that works off the reverse lights.

In it's natural state (in the driveway, unenergized) it doesn't seem to be letting fluid through. I just wasn't sure if they could be cleaned out, blown out or if my only recourse was to replace.
Click to expand...


If your solenoid has a rubber line on it going back to the MC fluid reservoir, it is a Normally Closed one, releasing pressure back to the MC when energized. If the lines go into the solenoid and out to the brake system, then it's the Normally Open type, closing and blocking the fluid to the brakes when energized.

If the MC had crud in it, then it may have gotten lodged into the small opening in the soenoid valve. A rule of thumb, if if MC is old and gunked up, requiring replacing the MC, chances are that it's time to replace the solenoid, also, since the same crap gets into it.
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Surge Brake Solenoid

barthel said:
Not sure what the "actuator" is. I replaced the the master cylinder...
Click to expand...

The Actuator is the part between the trailer tongue and the ball.
Essentially another name for the master cylinder.
Technically it is the master cylinder and the coupler and everything else on the front of the tongue.
 
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