heading back to home and suddenly a weird high frequency noise in cabin.

and finally i found the noise is under the hood from right headlight. and i found the coolant cap is off.......



and weird high frequency noise keep screaming....youtube below.

Had the same noise. Itīs the secondary air pump about to quit on you.

what is this secondary air pump use for??

and i am very surprised the coolant cap is off....

Do a search. I donīt think the coolant cap has anything to do with it.

the noise is from the aux pump for the heater. you can see it in the picture you posted.

secondary air pump is located on the left hand side of the car (US driver side)

I was sitting under a street light one night and started it up. I thought "Damn that's a loud street light!". It was my car...

My car is in the shop, shall I replace something before another part leaves me stranded?

i had to replace that just because it was annoying and always caused a CEL...

its only for when its cold out and regulates rpm or something like that. either way its easy to change and you can source a used one of a any amg or even 550's as a ton of them are interchangeable

If its the sec air pump turn it off via star

haha, this is funny

hi shardul

is it safe to drive it with this pump is failing? and do you have part# for this pump?

yes it is safe to drive as long as the source of the noise is the aux heater circulation pump.

A2118350264

is this the correct part?

Brand New Secondary Air Smog Pump For 1999-2007 Mercedes Benz V6 & V8 Oem Fit SP05

the one you posted is for SMOG pump

weird - the links I'm finding for #A2118350264 are showing as a water pump

read all my post on this thread carefully.... it is an aux circulation pump

we found out the reason...

it is the heater pump screaming because of low coolant.

we are sure that the coolant was draining off from the popped off weistec tank cap during the engine was still in operation, and i was driving back home.

now we fill back coolant, and also removed the air inside the cooling system. everything is fine, and temperature is keep in 80~90c qithout screaming pump.

I have this high frequency noise as well, sounds very similar to video posted. It has been driving me nuts trying to locate, thought it was idler pulley, or sbc unit but i think Shardul is right. Mine is intermittent, my coolant level is good, I ordered the pump last night so i hope that solves it...

hi verminator

you have to make sure there have no air in the cooling system. we checked the tank, and see the water is full visually. but we pour the water from another end, there have a lot air coming out from the tank, and finally we fill a lot water in it again.

ed

smartyin - where did you add coolant, directly to the radiator? I usually just make sure my surge tank is full, I can check the old fashioned way and run it with the radiator cap off and wait till the thermostat opens and make sure the level is good - is that how you added coolant? Thanks.

yes that is how you do it on a car with a stock cooling setup

I just checked my car and unless i am missing something....there is only a cap on the surge tank, coolant is full there and there is no cap directly on the radiator, never noticed before...so i guess i will wait till monday and put the new pump in...i will report back then, thanks.

No easy win on the aux heater circ pump. I replaced it and still have this intermittent high frequency screaming noise. It has to be something on the serpentine belt line....going for the double idler pulley's next along with the serpentine belt. I will check all the other spinning items and will hope it not the ac compressor or alternator bearings going bad...Happy Holidays all!!!

In my efforts to eliminate my high frequency noise it was time to look at the idler pulley's. I ordered a set of idlers from Eurocharged. The quality was very good, thank you Eurocharged! The outer pulley for the supercharger was loose when i checked it. All the other wheels in the belt lines were good. I replaced both pulleys and belts. Started her up and no more noise. Merry Christmas to me and my E!!! Happy Holidays to all and best wishes for a Joyous and Healthy New Year!!!