pulse every few seconds

[brosher]

I'm not sure what this is. It's not really that noticeable, but when sitting at idle I can feel a pulse of some kind. It happens about every 4 seconds and I feel it through the pedals in the footwell. When I rev the engine it does not occur. I'm thinking it is fuel related? Or maybe something funky is going on with the climate control?

[Bimmer Nut Ed]

Bump to top.

Does the idle change. What is a pulse, noise, feeling, tapping, a click.

Just trying to get the guys a better description of what you're talking about.

Otherwise, turn the volume up and ignore. j/k

[DaveVoorhis]

Sounds like the heater control valve opening and closing, though I've only heard it in my E34s when the engine isn't running. In my E28, it made a solid thump that could be heard and felt at idle.

See if the rate of thumping varies depending on where you set the cabin temp controls.

[Paul in NZ]

i reckon it is the heater valve(s) I noticed this the other day.I only notice it if i have the radio off.Its is a distant light thump.I found it when i arrived at home(i never open the bonnet(hood) in a public place ;)),opened the bonnet while leaving the car running and verifying it was "thumping"I traced it to the heater valve,put your hand on top of the valves and you will feel it.I think its the first signs of a sticky/failing heater valve

[Spasso]

I hear a cycling sort of thump/pulse like that in my E34 for a few seconds after I shut it off. I sounds like it's coming from the central firewall area. I'm guessing it is heater or cooling system related. It might be the cooling system self-purging to the header tank (V8).
Everything works, no leaks and no overheating so I'm leaving it be.

[brosher]

Hmm, I'll have to check out the valve. Can anyone describe how the valve works and why it pulse? Why is it a sign of failure?

[DaveVoorhis]

The valve unit consists of two solenoid-operated valves, one for the driver's side and one for the passenger side. The valve is opened and closed; the ratio of opened to closed time determines the temperature. The longer the valve remains open the more heated coolant flows into the heater matrix and the hotter it gets.

It normally clicks when opened and closed, but I suppose it could wear and start clunking.