My car has developed a pulse

[Snakeyestx]

Last night went out to dinner and I'm sitting at a red light and suddenly I feel a very subtle 'thump' on both the brake pedal and steering wheel. There was construction nearby so I didn't really think anything of it. A few miles later, another red light, another 'thump' (it's ever-so-slightly audible as well). This time even my girlfriend can feel the difference over the lumpy idle.

The 'thump' comes in intervals every 3-4 seconds while I'm sitting still. It seems to only happen while I'm stopped. About halfway to my destination it stopped doing it, but this morning on the way to work it came back. Steering and brakes feel fine, but feeling the pulse in both the wheel and brake pedal leads me to believe it's got something to do with the hydraulics (p/s p/b circuit).

Anyone ever experienced this before? Ideas?

[TSMacNeil]

I've not felt it yet...but I agree with your conclusion. How's the filter?
Wondering if a clogging filter would result in the pump pulling a little vacuum, which might feel like a bump.

[Bimmerguy2002]

What did you end up getting to eat?

[Snakeyestx]

What did you end up getting to eat?

Sushi.. Tuna, Salmon, Unagi, Yellowtail, Shaggy Roll (Shrimp Tempura roll with spicy mayo), some new thing they call their Godzilla roll (tempura salmon, unagi, spicy mayo), 3 caraffees of hot sake, and a happy girlfriend

[Snakeyestx]

I've not felt it yet...but I agree with your conclusion. How's the filter?
Wondering if a clogging filter would result in the pump pulling a little vacuum, which might feel like a bump.

I've got a spare new filter so I'll start there. I was thinking somewhere along that line too (filter backpressure buildup or something).

[jimoreno]

I think what you are feeling is what I have felt on mine on several occasions. I don't believe it is related to the PS system. I think it is the ABS systems giving a pulsation for some reason. After I changed the rear hubs in my car it hasn't done it again. Was there gravel or a water puddle where it did this?

[Rich Euro M5]

What did you end up getting to eat?

Sushi.. Tuna, Salmon, Unagi, Yellowtail, Shaggy Roll (Shrimp Tempura roll with spicy mayo), some new thing they call their Godzilla roll (tempura salmon, unagi, spicy mayo), 3 caraffees of hot sake, and a happy girlfriend

You're not a Sushi connoisseur, a traditional sushi roll always have the nori on the outside. A roll that's rice on the outside with a small wisp of nori inside is American, and isn't sushi. Anything with Mayo or cream cheese in them is Americanized crap, and IMO, it shouldn't be legal to represent it as sushi.

What does a true lover of sushi order, Amaebi, prepared in the traditional manner. And if you're wondering if the heads are a garnish, no they are not, you eat them as well. If your favorite sushi bar does not serve Amaebi, find a new establishment.

[Justin_FL]

My 535isA did this when I first bought it 6 years ago. I replaced every rubber hose in the hydraulic system (except for the high pressure ones as they were fine and not leaking). Also installed a new filter while the reservoir was empty. Power steering and brake boost was much more consistent afterwards.

[Rich Euro M5]

My 535isA did this when I first bought it 6 years ago. I replaced every rubber hose in the hydraulic system (except for the high pressure ones as they were fine and not leaking). Also installed a new filter while the reservoir was empty. Power steering and brake boost was much more consistent afterwards.

X2

[John in VA]

The heater valve will also "pulse" - more obvious when the car is stopped/quieter. With the engine running, feel the electrical connector on the heater valve.

[CharleyDog]

Thanks for helping me find this thread, Searchy.

I'm hoping you gents have sorted this problem out, because I'm getting the same thing on my e32. Shogun at Bimmerforums has been helping me out but I just had to post it here too because the systems are pretty close between the e28 and e32.

I start the car (1989 750iL). Ten seconds later the hydraulic pump starts loading up---you can hear the RPM decrease slightly---and then it unloads, causing the high pressure line from the pump to the regulator to flex and actually slap the wheel well next to it. It repeats every 8 seconds or so, regardless of whether the car is stationary or the brakes are applied. Otherwise, brakes and steering seem fine.

I've visually inspected the two pressure sensors, reset the ABS module, and checked the Pentosin level. This is on a car with ABS, ASC, and hydraulic leveling, but no traction control.

Anybody seen this before?