Solved - bad engine noise!!

bluecoupe30! said:
What an education! So pleased you solved this one, and at a relatively cost and time effective manner. This means to me, at least, that exhaust brackets absolutely MUST be moved up the check list whenever some angry noise of some unknown origin, starts to express itself!
Click to expand...
100% - the various components and connections can make all kinds of unsettling mechanical sounding noises.
 
Steve
Even after all your hard work and head scratching you went through, glad it ended up inexpensive and relatively easy to fix. It certainly could have been much worse and thanks for sharing. It will probably save others a lot of time and frustration.
Dan
 
That is awesome news. Noises like that can make you think the worst but what a relief when you find something like that! At least you got a good eye on everything else! Glad you found the issue.
 
Glad you resolved the mystery. It was another forum thread that brought to mind a "related" mystery. https://e9coupe.com/forum/threads/heartbreak-broken-rear-shock-mount.18208/

Many years ago, we had a curious encounter with an E9'r trying to diagnose what he thought was an abnormal engine noise. On an early Sunday morning drive, when few cars were on the road, we noticed a beautiful Polaris E9 being driven so that it was swaying from one side of the road to the other. This seemed deliberate rather than someone who had little control over his faculties. He eventually pulled to the side of the road and suspiciously circled the car. When we approached him, the driver explained he was hunting for the source of an abnormal engine noise. I did not hear the noise, but evidently, the noise seemed loudest in some but not all gears and did not seem related to any specific driving style. When the driver retrieved a flashlight from the rear of his vehicle, I noticed what seemed like unusually tall protruding threads at the top of one shock absorber. This was followed by discovery of (easy-to-overlook) jagged hairline cracks on both shock towers.

At rest, there was nothing obviously wrong. However, both towers were kaput. Suspension travel, given the right circumstances, permitted the exhaust to contact the body. The resultant sound evidently resonated so that it was mistaken for an engine noise. Possibly worth noting , the E9 was apparently fitted with extra firm KYB gas shocks. Whether this caused or contributed to the problem is unknown. Due to age and no vehicle history, the problem could have preexisted latest shock installation. (One of my cars experienced a similar failure with the original extra soft Boges. The owners manual never specifically warned against railroad track crossings and other road hazards. :rolleyes:)


IMG_1372.JPG

IMG_1387.JPG


fc8456b03b8376c8987f966fdeeb1c10.jpg
djhd302g3p651.jpg
 
Last edited:
Well, I gues it's not always the exhaust, After a couple weeks on my back I got everything buttoned back up with nice blingy yellow zinc hardware, including a robust exhaust bracket based on @BarneyT 's design and the noise is still there. Doesn't make the noise when cranking but soon as the engine catches it does. Sounds aluminum-ish. I'll post a video tomorrow when I have a helper if I haven't jumped off a bridge in the meantime :p I'm going to take a break. Then I'll probably boroscope the cylinders again.
 
Check all the aluminum and steel for that matter, brackets attached to the block P/S, Alt, A/C etc not so much the pieces but the brackets themselves, make sure that where there are shorter bolts that they don't bottom out just as they are getting tight.

PS don't jump, you have to get this figured out !!

Thanks, Rick
 
stphers said:
Check all the aluminum and steel for that matter, brackets attached to the block P/S, Alt, A/C etc not so much the pieces but the brackets themselves, make sure that where there are shorter bolts that they don't bottom out just as they are getting tight.

PS don't jump, you have to get this figured out !!

Thanks, Rick
Click to expand...
Alt, Ps, and A/C are all on tight. Will check everything else before another listen tomorrow. If it sounds up in the head, it’s coming off to check for an imbedded m6 nut. If no nut in the head then I’ll jump!
 
My mantra guy recommends moving up to Palo Santo incense sticks. I started this for you last night but you may have to do it closer to the car. The smell is really nice.

I assume the fuel pump and water pump were eliminated long ago from the noise source options, right?
 

Attachments

  • palosanto - 1.jpeg
    palosanto - 1.jpeg
    55.2 KB · Views: 67
Last edited:
Arde said:
I assume the fuel pump and water pump were eliminate long ago from the noise source options, right?
Click to expand...
I think I'll need more than incense but I appreciate the ritual. Yes, the noise is up in the engine and I'll post video tomorrow
 
Decades ago I bought a VW Squareback with a tapping noise in the engine. I assumed it was a bad rod bearing and agreed to split up the engine with a friend to share costs. He'd get the upper end and I'd get the lower end. It turned out it was the bakelite/plastic base for the fuel pump making the noise. It's T shaped with the part that sticks down surrounding the push rod that rides on the distributor drive to actuate the pump. The part had broken and was jumping up and down along the drive rod making a tapping sound. Otherwise, the engine was in great shape. We needed the parts for our other projects so we took the rest apart.
 
I badly want to make one of these to radically simplify my troubleshooting routine. Endlessly useful!


That said, one of the tools I routinely use for pinpointing difficult to diagnose noises is one of these (apologies if someone has already proposed using this):

www.harborfreight.com

Mechanics Stethoscope

Amazing deals on this Mechanics Stethoscope at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
 
Here are a couple video snippets, the sound in video 1 is the random noise, youll hear a couple of sharp click noises during the clip. Until this point the noise was steady but it started doing random clicks when I filmed this one:



Then it went back to being steady. The noise definitely sounds like it is coming from the head area of the front 3 cylinders (not in the block), the loose nuts that could have come off and gone down the intake were on cylinders 4 & 5 so I am not sure how a nut could have gone forward and got sucked in. Not a pleasant sound:



It makes no noise when spinning the engine during cranking or with the plugs out, only when it fires up (loose valve or????). So my plan is to take another look at the valve train from the top side and if nothing is obvious I'll pull the head. Any input on above videos is appreciated!
 
stphers said:
I can't remember, is the compression all all cyls OK? Wonder if it is a cracked valve spring or really loose guide? So many different things

Thanks, Rick
Click to expand...
180-185 in all cylinders. Fan is free and clear as are belts. Yes - so many things.
 
You must log in or register to reply here.
Back
Top