94 Marada Mercruiser Power Steering Issue

wpeakjr

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Jan 18, 2014
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I have a 94 Marada with the 305 Mercruiser I/O. A couple of seasons ago the return line on my power steering busted, draining the PS pump and killing the bearing. I replaced the pump and both lines (supply and return lines). It seems to function fine in the garage with muffs on. I bleed all air from system. When I take it for lake testing, it blows the return line again. I cannot come up with a logical explanation for why this would happen. It blows the section of line after the cooler. The best I can tell there should be no pressure in this spot of the lines. Has anyone ever seen this before.
 

Bondo

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Re: 94 Marada Mercruiser Power Steering Issue

I have a 94 Marada with the 305 Mercruiser I/O. A couple of seasons ago the return line on my power steering busted, draining the PS pump and killing the bearing. I replaced the pump and both lines (supply and return lines). It seems to function fine in the garage with muffs on. I bleed all air from system. When I take it for lake testing, it blows the return line again. I cannot come up with a logical explanation for why this would happen. It blows the section of line after the cooler. The best I can tell there should be no pressure in this spot of the lines. Has anyone ever seen this before.

Ayuh,.... Welcome Aboard,.... The section 'tween the cooler, 'n pump, Right,..??

If ya pull that line off the pump, does fluid run out,..??
 

alldodge

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Re: 94 Marada Mercruiser Power Steering Issue

Mine did that and burned the pump. While the hose didn't blow back off it kept leaking on the return side due to pressure building up; and as you mentioned there should be no pressure on the return line. Pull the return lines off and blow high pressure air back through in reverse order. Also blow out the cooler. Since you replaced all the lines yu should not have any issue with soft lines.
 

wpeakjr

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Jan 18, 2014
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Re: 94 Marada Mercruiser Power Steering Issue

I will check that section of line. There isnt anything in between of the cooler and the pump. That is why it has been perplexing. It is even a straight line into the PS pump, as there is just a nipple for the line to hook into. I will let you know in a couple days. Still a s a little chilly out there in the garage! :)
 

NHGuy

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Re: 94 Marada Mercruiser Power Steering Issue

Did you keep the old fitting from the original return line and put it on the new pump? Perhaps there's some shrapnel in the system that is stopping in that line end. Maybe the fitting is blocked or crushed. Back flush and clear it. If it's questionable just get a fresh one.
It's also possible there is more c___ coming through from the rest of the system. Could have been in there from before.
I'd take apart the lines and blow them out, and as was said, back flush the cooler.
Also, you can try to back flush the power assist unit. It might not cooperate though because it has small orifices on it's inside.
To do that, wiggle the control valve actuator while blowing air or forcing fluid through there backwards. I wouldn't rush into that though. It sounds more like your blockage is at the inlet to the pump, or there's too much pressure in there.
The new pump would have a built in pressure regulator as part of it. So it's not likely you had two in a row with the same failure.
Here's a thought. The return pressure comes up with demand. And the demand happens when the control actuator is off it's center stop point. If the cable is bound up and the control valve is always pushed to one direction or the other the pump sends full pressure through for too much of the time. Normally the pressure isn't full, it only goes to full pressure momentarily while the wheel turns.
Does it sound as if the pump is laboring all the time? Does the steering wheel turn to it's stop when you start the motor? If so you could need to balance the power steering or free up the actuator pivot so it can center easily. To balance it there's a nut on the starboard end of the valve body under a little metal cap, it's behind the big cylinder. You just turn the nut a little to adjust the side to side balance so it stays in place with the engine running. If you have to fight the wheel underway you might have that issue.
Just watch out for the power steering arm when you go to adjust that thing, it can injure you. Make sure you can keep yourself away from the machinery.
I'll try to pull out the pages from my manual so you can see what I mean. I wish posting pdf's didn't take so many steps.
 
Last edited:

NHGuy

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Re: 94 Marada Mercruiser Power Steering Issue

See if these help you.
 

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