Picked up an 09 M1123 and the power steering is wonky

[sp00n]

2009 M1123 6.5 NA 4L80E in very good running condition. No leaks, none. Zero

The only problem I'm having with it is the power steering feels very much like it has air in the system/low on fluid- however the black lunar lander fluid reservoir typically near the fuel filter on the top of the engine is..just not there. There are no plugged lines, no leaks, and the lines to the steering box are hooked up. Truck definitely has *some* power steering as you can turn the wheel with one finger, but it makes about a quarter turn and then increases resistance then goes back to easy, in a pulsing pattern while you turn the wheel. Exactly like it's got air in it. The pump seems to be present under the 200a alternator, following the hoses did not reveal any reservoir to add/check fluid. Perhaps they updated the system and it's buried somewhere less than obvious? All the 2016+ trucks I have access to at work have the black reservoir right on top.

Like I said, absolutely no leaks or plugged dangling lines. Please advise

 

[Mogman]

Where are those two hoses going that are behind the Cadillac valve? those should be going to the reservoir.
Your pinky is just about touching one in the picture

 

[sp00n]

Where are those two hoses going that are behind the Cadillac valve? those should be going to the reservoir.
Your pinky is just about touching one in the picture

Down to what I assume is the power steering pump that also powers the brakes. It's a pulley accessory directly under the alternator. I can see a high pressure line and a low pressure return coming from that device. The lines feed the steering box, that Cadillac valve and the brake master.

I also want to note that my radiator fan is atypical as well: it uses a commerical light truck thermal clutch on the front instead of the hydraulic line that engages it off of a temp switch, like what I'm used to seeing under the hood. It cools the truck efficiently at least, not sure what to make of that.

 

[Mogman]

The PS pump has three lines in play one HP and two returns, if both of those return lines are going to the pump then there should be a reservoir cap between the alt and lower pulley, if it had the remote type pump there would only be two connections on the pump itself so both those return lines could not be connected, the remote type has two return lines to the reservoir and a single return/feed line to the pump.

Sounds like you may have a psychobilly truck

But then again I could be completely wrong

 

[sp00n]

The PS pump has three lines in play one HP and two returns, if both of those return lines are going to the pump then there should be a reservoir cap between the alt and lower pulley, if it had the remote type pump there would only be two connections on the pump itself so both those return lines could not be connected, the remote type has two return lines to the reservoir and a single return/feed line to the pump.

Sounds like you may have a psychobilly truck

But then again I could be completely wrong

This is how it came from the USMC out of Yermo. When I get off work I'll have to look again to see how the lines are routed specifically and I'll snag more pictures- I was kind of expecting to get told I was dumb it's right by xyz use the search function better.

 

[Mogman]

Detailed pics of the thermal fan setup!

 

[sp00n]

Detailed pics of the thermal fan setup!

The upside is there's no whine even when it's hot

 

[Mogman]

I would like to try a thermal clutch, especially if I could find one that fits the OEM fan.

 

[mgFray]

The reservoir is most likely on the hydraulic pump itself. Look straight down between the generator and the hose coming off the radiator. You should see a cap right on the pump. That is where you need to add fluid and keep it topped off.

I looked and I only have a picture of the pump from the bottom, so you can't see the cap or it's exact location from the top. If you need I can go out and take a picture of it on my rig. Just let me know. (My engine is a 6.5L w/ the 4 v-belts.. But otherwise it should be the same and one with a serpentine.)

 

[Coug]

Just to be sure, you have the pump that is supposed to have the remote reservoir, not the one with the reservoir built into the pump?
When the trucks go through reset the data plate gets removed and the new one showing the rebuild only has the rebuild date on it, not the original manufacture date.
If the serial number is below 196900, then it's supposed to be the older style with reservoir built onto the pump.

 

[TNDRIVER]

I would like to try a thermal clutch, especially if I could find one that fits the OEM fan.

I think I saw a HPG listing of what you wish. My guess its from the HUMMER. Bring your magic plastic.

 

[sp00n]

The reservoir is most likely on the hydraulic pump itself. Look straight down between the generator and the hose coming off the radiator. You should see a cap right on the pump. That is where you need to add fluid and keep it topped off.

I looked and I only have a picture of the pump from the bottom, so you can't see the cap or it's exact location from the top. If you need I can go out and take a picture of it on my rig. Just let me know. (My engine is a 6.5L w/ the 4 v-belts.. But otherwise it should be the same and one with a serpentine.)

Your description makes sense and I will look closer for a cap on the pump this afternoon. I will return with pics of what I have if I can't find it there.

 

[badger_610889]

I was shopping for a new pump for my A2 last week and discovered that some M998 (12339495-1) pump have a small reservoir integrated indeed.

The pump would have a cap similar to this:

 

[Mogman]

Yep, was a long time before they went to the remote reservoir

 

[Mogman]

I know we are not supposed to just tell you "go read the dang TM" but you will have a much better experience and probably spend allot less money just "swapping parts" if you would have made yourself familiar with the TMs applicable to your truck including the operators maintenance TM, while you were waiting on your truck to arrive, it's all in there.

 

[Coug]

Everything before serial number 196900 was originally equipped with the pump integrated reservoir. It wasn't until post 196900 trucks that the reservoir is up on top of the engine.
Some A2 trucks before that serial number did get the remote reservoir during rebuild for whatever reason, so it isn't always that serial number break.

 

[mgFray]

I went out and took a picture. With the 200 AMP generator the top of the reservoir cap is hidden pretty good. To fill it you need a long neck funnel, also be careful to not OVER fill!

(The manual has specifications on how to check the level. I don't remember offhand if it's check the level with the cap screwed in or just down on the top.)

 

[papakb]

Keep in mind that the pump used Dexron fluid and not Power steering fluid.

 

[sp00n]

Okay I found the reservoir behind the pump under the generator, derp. Mighty nice of them to bury it in there with no protruding fill neck. The level was in range on the stick despite the operation of the power steering itself having all the tell tale signs of being low on fluid, I'll attempt to bleed it another day when I have more time and fewer mosquitoes to deal with.

I was unable to snag any legible pictures of the thermal clutch on the radiator fan but it just looks like your standard Chevy Silverado aluminum fins surrounding a spring that gets hot and engages the clutch arrangement.

 

[Mogman]

Curious does the steering act the same in both directions? how about the brakes.
There is a special tool kit for the HMMWV that does not cost TOO much it has a test gauge setup to test the PS pump flow and pressure among many other handy tools to have.

NEW IN BOX Kippertool 57K0267 Vehicular Tool Kit - HMMWV HUMVEE 5180-01-387-5455 | eBay

Find many great new & used options and get the best deals for NEW IN BOX Kippertool 57K0267 Vehicular Tool Kit - HMMWV HUMVEE 5180-01-387-5455 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

It is interesting that so many have so much trouble with the steering pump/gear on the HMMWV, it is the same setup used for decades on civilian cars and light trucks and I have seen very few of those issues in all the years I have twisted wrenches.

When I put the GEP in the Detroit it whined for a little while like all PS units do when air is introduced but after a while it stopped like they usually do.
I just wonder what makes a HMMWV think it is so different...

In fact the systems are so similar that I used the PS test gauge on my 2008 Dmax one ton, after 300,000 as I suspected the pump is rather week, this accounts for the sluggish steering and the additional pressure required on the brake pedal.