Power steering cap pressurized, normal or no?

[03coloradowrangler]

original 03 Mercedes power steering setup on 03 4.0 with 200k

Recently I had noticed a leak at the pitman arm shaft of the power steering gearbox and have Been keeping a eye on the fluid levels since. have noticed I get about 4-5 drips once parked for a hour or 2. I have no idea how long ive been leaking but suspect less than 4 months as im under it fairly often in warmer weather.

what I have always noticed when removing the what I believe to be oem power steering fluid cap is a pressurized hiss no matter if the engine is hot or cold. being that I have a leak now I am beginning to wonder if a pressurized system may be contributing to my leak. if I park the jeep, twist the cap off to burp then reinstall the cap I dont get any drips but just a weep at the pitman.

question being, is the cap supposed to be a venting cap or sealed? obviously when the fluid gets warm it expands some and Id expect pressure should be venting, not staying constant.

is there a vent hole I should check for in the cap or should I be looking to replace the power steering cap due to some sort of failure?

 

[red02tj]

When I had a leak in my 02 I replaced the cap Crown Automotive 4897287AA... https://www.amazon.com/dp/B008VPYMHI/?tag=wranglerorg-20

And then did this
https://wranglertjforum.com/threads...boxes-on-rockauto-any-good.55766/post-1004357

It’s a quick and cheap sanity check before you go further. I’ve been leak free for 3months.

 

[SvtLdr]

My steering reservoir does the same thing, slight hiss as pressurized air escapes. I think this is normal. I don't think a vented cap is necessary. The power steering is pressurized from the pump, so even if the cap were vented you wouldn't solve anything downstream where you're seeing the leak.

 

[03coloradowrangler]

When I had a leak in my 02 I replaced the cap Crown Automotive 4897287AA... https://www.amazon.com/dp/B008VPYMHI/?tag=wranglerorg-20

And then did this
https://wranglertjforum.com/threads...boxes-on-rockauto-any-good.55766/post-1004357

It’s a quick and cheap sanity check before you go further. I’ve been leak free for 3months.

I have considered adding stop leak, but im also hesitant to add any additives to the steering system. id honestly much rather spend the money on a seal kit or new gearbox. but purchasing a new gearbox is also a gamble too.

My steering reservoir does the same thing, slight hiss as pressurized air escapes. I think this is normal. I don't think a vented cap is necessary. The power steering is pressurized from the pump, so even if the cap were vented you wouldn't solve anything downstream where you're seeing the leak.

thank you for confirming yours also hisses. im just checking my sanity.

all in all I dont believe the cap to be my problem. im plenty sure 200k wear is the problem. just sanity checking that the cap may be faulty too.

 

[SvtLdr]

original 03 Mercedes power steering setup on 03 4.0 with 200k

Recently I had noticed a leak at the pitman arm shaft of the power steering gearbox and have Been keeping a eye on the fluid levels since. have noticed I get about 4-5 drips once parked for a hour or 2. I have no idea how long ive been leaking but suspect less than 4 months as im under it fairly often in warmer weather.

what I have always noticed when removing the what I believe to be oem power steering fluid cap is a pressurized hiss no matter if the engine is hot or cold. being that I have a leak now I am beginning to wonder if a pressurized system may be contributing to my leak. if I park the jeep, twist the cap off to burp then reinstall the cap I dont get any drips but just a weep at the pitman.

question being, is the cap supposed to be a venting cap or sealed? obviously when the fluid gets warm it expands some and Id expect pressure should be venting, not staying constant.

is there a vent hole I should check for in the cap or should I be looking to replace the power steering cap due to some sort of failure?

I'd say the fact that the gear box leaks (regardless of burping the air in the reservoir) would point to a worn seal.

 

[SvtLdr]

I have considered adding stop leak, but im also hesitant to add any additives to the steering system. id honestly much rather spend the money on a seal kit or new gearbox. but purchasing a new gearbox is also a gamble too.

thank you for confirming yours also hisses. im just checking my sanity.

all in all I dont believe the cap to be my problem. im plenty sure 200k wear is the problem. just sanity checking that the cap may be faulty too.

I'd say your on the right track and your sanity is in good shape.

200k on the OE box ain't bad. Mine is still original also with 220k on it. Still leak free, I'd say I'm on borrowed time.

 

[red02tj]

I’m also against additives and wouldn’t use them in the engine or cooling system but according to many on this site the PS leak stop is fine.

RE the cap, mine had rusted apart and needed a replacement.

 

[03coloradowrangler]

I'd say the fact that the gear box leaks (regardless of burping the air in the reservoir) would point to a worn seal.

definitely. just checking if I have a separate issue with the cap ive not thought of.

I'd say your on the right track and your sanity is in good shape.

200k on the OE box ain't bad. Mine is still original also with 220k on it. Still leak free, I'd say I'm on borrowed time.

ive looked around a little bit. cant budget a gear box at the moment. kinda anal with oem parts too. looked at used salvage pumps off ebay but mileage is the same generally if not more.. or the photo shows a nasty front end collision and who knows what was ran through the pump beforehand. and remans are up in the air too. ive got a redhead box in my pickup after finally wearing out at about 284k miles but ive only put probably 100 miles on it this year if that so I dont know how they handle long term.

I’m also against additives and wouldn’t use them in the engine or cooling system but according to many on this site the PS leak stop is fine.

RE the cap, mine had rusted apart and needed a replacement.

View attachment 305691

ive definitely considered stop leak but ive also questioned myself not to. I do use high mileage oil in the engine... but I feel dirty considering adding anything to a pristine clean ps setup. how does one develop rust in a sealed power steering environment.

 

[SvtLdr]

On a somewhat related topic, does anyone know the capacity of the entire power steering system? I'm getting ready to add a cooler and am curious how much fluid I'm starting with?

 

[red02tj]

how does one develop rust in a sealed power steering environment

It’s an 02 that had 32k miles when I got it 3 months ago, not quite a barn find but definitely some questionable “maintenance” by the PO.

 

[SvtLdr]

how does one develop rust in a sealed power steering enenvironment.

Condensation can build up in the air pocket above the fluid in the reservoir.

 

[SvtLdr]

I would also suspect that, over time, the fluid will absorb moisture? Kinda like brake fluid does.

 

[sab]

On a somewhat related topic, does anyone know the capacity of the entire power steering system? I'm getting ready to add a cooler and am curious how much fluid I'm starting with?

@SvtLdr - I just checked my notes (a spreadsheet) on fluid types and capacities, and I have a question mark for PS fluid capacity. When I bought my LJ last June, I embarked on changing all the fluids. I've done them all except PS fluid (and clutch, which I understand now is not meant to be changed) at this point. I searched everywhere for capacity info and never found it. I know - a long-winded post to say, "I don't know," but that particular spec was very elusive to me. I'm also interested to know the capacity, if it's known...

 

[03coloradowrangler]

I would also suspect that, over time, the fluid will absorb moisture? Kinda like brake fluid does.

possibly. not sure on ATF/power steering, ive always been warned about brake fluid. but 32k seems like its too fresh... but then again thinking about it, sitting in the warm and cold I guess water could work its way in.

 

[pagrey]

I don't think power steering fluid absorbs moisture, it's like ATF, mine even is ATF. It gets warm enough it should boil off water although I don't think water in the system is too common. Depending on the cooler you get it might hold a significant fraction of the system capacity. I changed mine when I added a cooler, it wasn't more than two from what I recall. The FSM says depending on lines and coolers the capacity varies which makes sense, the reservoir is tiny.