Author Topic: Wierd hissing noise (Read 5722 times)

nedtheviking · « **on:** October 27, 2007, 02:31:49 PM »

Hey guys so i've really enjoyed living with the e30 for a couple weeks now. unfortunately last weekend it failed inspection, my muffler decided the night before i got it inspected was a good time to open up a rust hole. i tried to fix it with cold weld and a sheet metal patch, but it didnt work, and when the cold weld heats up it smells absolutely awful (at least i hope thats what the smell is...)
anyway, the main point of this thread (which has nothing to do with my exhaust) is that i have a hissing noise coming from the engine, i can only hear it if standing outside the car while its idling. i used a screwdriver butt against my ear to try and figure out where it was coming from. they valve train sounded fine, and it didn't seem to be coming from the chain either.
I think maybe its a vacuum leak? but the car idles fine, no hesitation when driving or anything.
any ideas?

Also- i know this isnt related buy why does pelican parts sell a timing chain tensioner spring seperately from the tensioner piston? does the piston come with a spring or do i have to buy both of these parts? could i just buy the spring and put it in my old tensioner? thanks.

11-31-1-743-187-M40
11-41-1-706-809-M9

nedtheviking · « **Reply #1 on:** October 27, 2007, 02:46:17 PM »

sorry to post again, but i didnt want to start a whole new thread. I can hear my fuel pump if im sitting in the car and its idling, its not very loud though (not as loud as when its first pressurizing the car when the ignition is on, which is does quickly) its kind of loud if you listen under the gas tank while the car is idling. i have never had an e30 before so i dont know if this is normal noise or indicative of immediate catastrophic failure, etc.

ak96ss · « **Reply #2 on:** October 28, 2007, 06:01:46 AM »

I don't believe the tensioner is serviceable; it's cheap enough, I would just buy a new tensioner, particularly if you still have the original one.

My fuel pump gave me no warning at all when it failed. It just stopped on the way to work one day. I would just keep it in mind, maybe pick up a new one to have on hand for the day when it does fail.

D. Clay · « **Reply #3 on:** October 28, 2007, 11:28:28 AM »

Fuel pump sounds like normal noise. A short 1-3 seconds when the key is turned and it builds pressure. It makes noise when running but it's hard to hear over all the normal M42 noises inside the car. I tell people sometimes that a 318is isn't typical of BMW's from the standpoint of being luxury cars. It's noisy and rides rough. Most people think of BMW's as luxury cars with performance. The 318 is a more immediate and visceral sort of thing.

silverblades181 · « **Reply #4 on:** October 28, 2007, 03:02:00 PM »

Did you check the belts and pulleys?

nedtheviking · « **Reply #5 on:** October 28, 2007, 10:27:03 PM »

hey guys thanks for getting back to me. I'll just get the whole tensioner, and hope for the best with the fuel pump. and I'm very glad the 318is is more visceral, my friend has a e39 540 which he loves, but I've always found it very beautiful but a wee bit boring. (I've never driven it 'spiritedly' though).

silverblades- i looked at the belts, and they looked fine, although i don't really know what to look for per se. I always thought belts squeaked, I've never heard of them hissing. how should i check them though?

silverblades181 · « **Reply #6 on:** October 29, 2007, 06:37:36 PM »

Quote from: nedtheviking;36776

silverblades- i looked at the belts, and they looked fine, although i don't really know what to look for per se. I always thought belts squeaked, I've never heard of them hissing. how should i check them though?

Well maybe I misunderstood the noise your hearing..to me belts do a hissing sound. I guess you'd know if it was a belt sound. As for what to look for, check for cracks and a noisy pulley.

Grizo · « **Reply #7 on:** September 27, 2012, 02:19:00 AM »

Reviving this old thread but ffffuuuuu my car has this hissing noise! Can't find any threads about it. And this one was inconclusive! I've run my car with all the belts and fan clutch off and it still makes the noise!

DesktopDave · « **Reply #8 on:** September 27, 2012, 06:59:59 AM »

Offhand I'd check the FPR - they can hiss as fuel passes through them.

I use a 'mechanics stethoscope' to check stuff like that. You get a big screwdriver, put the tip on what you'd like to listen to, then put the handle into your ear. It sounds dumb but works surprisingly well - just be careful of high voltage. It's best for fuel injectors but I'll bet you could use it to chase this little hissing down.

Grizo · « **Reply #9 on:** September 27, 2012, 09:52:05 AM »

I will definitely try that. Is the FPR rpm related?

DesktopDave · « **Reply #10 on:** September 27, 2012, 05:00:56 PM »

Yep - it's related to RPM but not directly. The FPR should bypass less fuel as the motor RPM increases under load. It's designed to raise fuel pressure to compensate for intake manifold vaccuum as well as bleeding off excess pressure from the fuel pump.

When I got my car a few years ago it didn't run at all. I shorted the main & FP relays to troubleshoot...I was surprised by the amount of noise the FPR made as it routed all fuel back to the tank. Of course in that case the motor wasn't using any fuel at all.

Grizo · « **Reply #11 on:** September 27, 2012, 08:27:52 PM »

Was it an intermittent noise or constant? Mine is intermittent.