Steering effort seems high - How does variable assist work?

just purchased an '11 DCLB SR5 with 175K When I test drove, the steering was tight. After driving home an hour, it was better. However, assist seems pretty low compared to what I am used to. This vehicle has the variable assist option and expect much more assist when manuevering at very low speeds. It seems that the assist level is the same at all speeds. I jacked it up and the effort with the engine off and wheels off the ground is very light, so no mechanical issues. Seems to be a low pressure issue. Belt is a tad looser than I would expect, but not really loose. No noises of any kind to point to a belt, so question pump issues or a failure of the variable assist function. At highway speeds the tension is just right, so wondering if there is an issue with the variable system not increasing the pressure at low speeds or a stuck valve that is keeping it at the lower pressure used for high speeds. Does anyone know how this system works? THe only electrical wire I can find is the pressure sensor on the pump. Cannot figure out how the system provides the variable assist, so don't know how to troubleshoot. Can anyone shed some light on this?

To help clarify this, when turning to get out of the driveway, the effort is only slightly better than the cars I have with manual steering.

Thanks in advance.

 

Welcome to the forum!


Maybe there is only one wire controlling
The hydraulic from the power steering pump. Not sure

Perhaps it's in this spot on the steering rack

Was just a quick internet search but something perhaps for a place to start looking
Good luck

Maybe the fluid needs a flush/drain refill?

 

A VERY helpfull contribution. Thanks so much. That last pic has me thinking I need to pull the skid plate and have a look down there. Lookd at pics of reman racks and none have solenoids like the Buicks have, nor did the pics show a bung for one in the high pressure line. Maybe it is inline lik that pic. Flush is also a good idea. When we picked the car up, the steering was VERY tight and it loosened up a decent amount whn we got home two hours later. Maybe there is varnish in the valve causing it to hang up. records show that the original fluid wasn't changed until 130K - WAYYY to long for a PS system.

 

I just had my whole rack replaced last week.the rack rusted out where the lines go in . 2k later its all better. Hope you find a cheaper fix

 

Maybe I’m misunderstanding, but there is no electronic assist on your truck. I’ve had my rack out more times than I can count, and it’s a basic hydraulic system, no electronics. The one wire you found on the pump is for a pressure switch that will bump the rpm’s a smidge to help turn the rack by spinning the pump faster.

 

you are likely correct. However my truck has a line item on the build sheet that says it has a unique capability called ps variable assist and toyota claims this adds more assistance at low speeds than it does at high speeds. I was guessing it was electronically controlled pressure but maybe not. $10000 question is HOW do they do it? Seems unlikely that they just made it up to have more features. Apparently this was only offered on 2010 and up models so not all of us have it. What year is yours? All the gm units i have seen with this capability use a solenoid on the rack.

 

I’m pretty sure the Tacoma has a linear hydraulic rack. This is not an Audi with electric servotronic.

 

Turns out some shop put power steering fluid in it instead of atf. Used a chemical flush , drained and re-filled with atf. Much better ow

 

No.

"The one wire you found on the pump is for a pressure switch that will bump the rpm’s a smidge to help turn the rack by spinning the pump faster."

 

Yes, I get that and wasn't suggesting that sensor was for variable assist. It seemed obvious it was just a pressure sensor. I stated that Toyota says it has variable assist and was trying to figure out exactly how this is accomplished. All other implementations of it that I have seen used solenoids of some sort or electromagnetics to add or reduced friction on the torsion bar, but find none of that on the tacoma.