For enthusiast of the Classic GMC Motorhome built from 1973 to 1978. A web-based mirror of the GMCnet mailing list.

Home » GMC » GMCnet » [GMCnet] Warning for My Electric Wiper Customers
[GMCnet] Warning for My Electric Wiper Customers [message #326658] Sat, 02 December 2017 20:12
Ken Henderson is currently offline  Ken Henderson   United States
Messages: 7318
Registered: March 2004
Location: Americus, GA
Karma: 41
Senior Member
Yesterday a side effect of my electric wiper upgrade bit me:

Yesterday I finished the major, in my case, task of installing 3 new
batteries after having just completed the PS pump repair I reported here.
Feeling the need for a test drive, I headed toward the service station for
a fill-up. At the second stop from my house, on un-divided 5-lane US-19, I
suddenly lost brake boost! And steering boost!

Fortunately, I was in the left turn lane with no one ahead of me and with
no cross street, so my very wide almost-U-turn into the side street wasn't
a hazard to anyone but me. There was a driveway immediately to the right
after the turn, into a large vacant lot. I was able to stop the coach
slowly, with both feet firmly on the pedal. The dash gauge showed I was
producing about 200 psi of hydraulic line pressure -- an ordinary gentle
stop requires about 400 psi.

Outside I found oil pouring all underneath the front of the coach. Raising
the driver's side hood showed the source: Everything from the Hydroboost
down was covered in power steering fluid! "Probably a rupture in the high
pressure line to the Hydroboost I've been running for the past year or

Being only 3 blocks from home, with only gentle hills and little traffic, I
decided to drive home, using my pneumatic brake pedal puller to help me if
necessary with the brakes. That extra 140 lbf on the pedal would give
reasonable stopping distances if I drove very slowly -- with the flashers
going. I knew from the 80 miles or so I drove on the Olympic peninsula in
'13 with no power steering that I could make the turns.

Back home I pulled the master cylinder away from the Hydroboost, then
removed the vertical bracket which conceals the hydraulic connections.
Everything looked OK, so I refilled the PS reservoir and cranked the
engine. After I hurried outside to see where the leak was, I rushed back
to kill the engine. There was a gushing stream of fluid from the power
steering box area!

Long story a little shorter: The power steering return hose had come off
of the tubing elbow which screws into the steering box That 3/8" elbow,
with a male flare nut on one end and a tube-retention bulge ("bulb") on the
other is part of my electric wiper kit. It facilitates elimination of the
hydraulic motor, which normally is plumbed between the steering box and the
power steering pump's reservoir.

For a while, the company which manufactures those elbows for me had
difficulty making adequately prominent retention bulbs. Most were big
enough, but every production run had some which I considered marginal;
others were almost non-existent and I refused to use them. That problem
has been solved for quite some time, but I had installed one of those with
almost no bulb on my own GMC, expecting there to be no problem with it.

There should NOT have been a problem, because the only pressure on that
connection is that caused by the fluid flowing through 36 inches of 3/8"
hose into the unpressurized reservoir -- almost zero -- ordinarily.

But there seem to be few "ordinarily's" in my life: The Hydroboost is
plumbed between the power steering pump and the steering box. It has a
return to the reservoir for when it's operating (brakes applied), but it
always passes full pump pressure on to the steering box. From the steering
box, the return line which should go directly to the reservoir, per
original design, goes to a oil-air cooler, then to an in-line filter,
before reaching the reservoir. :-( Yep, there can be a LOT more pressure
on that return line. In this case, I forgot that I had an elbow installed
with an inadequate bulb to retain the hose under pressure. And I got bit.
Fortunately, the only cost was a can of PS fluid and the necessity to
pressure wash the entire underside of the coach today.

SO, for all my past Electric Wiper customers: IF you install Hydroboost,
or otherwise restrict the return flow path, PLEASE be sure your elbow has a
prominent bulge, and that the hose clamp is securely tightened on the
steering box side of that bulb so the hose CANNOT slide off. If you find
an inadequate bulb, let me know and I'll provide one of the current
production, which have a more-than-adequate one.

This is the only way I have to notify buyers, so if you know someone with
my wipers who's not frequently here, please pass the word.

Ken H.
GMCnet mailing list
Unsubscribe or Change List Options:

Ken Henderson
Americus, GA
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
Previous Topic: GMC Greater Midwest Classics 2018 Rallys
Next Topic: [GMCnet] Vacuum hose etc. by entrance door...
Goto Forum:

Current Time: Mon Dec 11 20:41:01 CST 2017

Total time taken to generate the page: 0.12279 seconds