WHY
DOES YOUR MARK VIII LEAK DOWN ONE DAY, BUT NOT THE NEXT?
Its
hard to explain, but the location of the fold of the rubber (where the rubber
bladder on the strut wraps around on the bottom) changes with vehicle height.
The entire rubber bladder, is only 12 inches long and only about 1 to 1-1/2 inches
of this bladder is dry rotted. The majority of wear or dry rott, is where the
fold of the rubber was at MOST OF THE TIME.
The
picture below shows a strut compressed some. This would be an example of "trim
height". You can see the cracks on the fold of the rubber magically appear
and open up and if the strut had air in it, would leak air.
AN
AIR STRUT COMPRESSED SHOWING THE CRACKS BEING EXPOSED ON THE FOLD OF THE RUBBER,
SIMILAR TO WHAT IT LOOKS LIKE AT HWY SPEEDS.
(ABOVE
55 MPH)
Below,
you'll see that when the strut is extended, which is an example of "city
height", you can't see any cracks. This is because the cracks ARE NOT exposed
or opened from the fold of the rubber, and the cracks will actually seal.(in early
stages anyway)
AN
AIR STRUT EXTENDED, SIMILAR TO HOW IT LOOKS AT "CITY HEIGHT" OR THE
RAISED HEIGHT.
(NO
CRACKS VISIBLE)
WHY
DOES IT LEAK AT HIGHWAY SPEEDS BUT NOT AROUND TOWN?
While
the engine is running, sitting still or driving the car at lower speeds, like
through the city and even parking lots, the car needs additional ground clearance
to clear manhole covers, potholes and such. I call this "city height".
The car will raise to this height automatically when the car is started and stay
at this height until the speed gets to approx. 65 mph. After the car reaches 65,
the car will lower (1 full inch '93's up to mid '94, 1/2 inch after) to make itself
more aerodynamic. The car will be at this lowered height anytime after 65 mph.
I call this "trim height".
When
the car is taken off the freeway, or below 45 or so for awhile, the car will raise
back up to "city height" and stay there until either the car is driven
to hwy. speeds again or until the car is parked and shut off. After the car is
shut off and the door is closed, the system will lower to trim height again, which
is the same height as it drops too at hwy. speeds, and stay there until the car
is started again.
QUESTION:
WHAT HEIGHT DOES THE CAR STAY AT MOST OF THE TIME?
ANSWER:
Trim height. (where most of the dry rotted area is)
Lets add it up.
The
car sits for what, 14 hours after you come home at "trim height", plus
it sits at "trim height" anytime while at 65+.
The
ONLY time the car is at "city height" is while the car is running(even
idling) and while driving at lower speeds. Even if you say, 1 hour to work, 1
hour home, 1 hour after work to go to the store and whatever, the car is hardly
at "city height".
So
basically out of a 24 hour period, the car was at "city height" for
only 3 hours, but the car was at "trim height" for 14 hours or so overnight,
plus anytime the car was over 65, plus the time during the day when the car sat,
while at work.
