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View Full Version : Faint knocking sound coming from the left side of the engine at idle.


KGB
02-09-2005, 11:28 AM
I have a '97 540 6-speed with 84,000km on it, bought it used last November.

I noticed awhile ago that the passenger side of the engine is making a faint but audible knocking sound during idle. It's not really easy to distinguish because of the overall peripheral sound of the engine running. However, I can definitely pick it up since my hearing isn't that bad. Just this morning when I parked the car it seemed to me that the knocking became more pronounced, or maybe I'm wrong, I can't tell exactly. The car seems to have plenty of power with good acceleration on high speeds.

Revving the engine doesn't eliminate the knock, just changes the its speed and drowns the knock out in the revving hum of the engine.

Another thing. When the car is parked, turning the steering wheel even slightly also affects the speed of the engine running, it goes slightly below 500 and starts to shake sometimes. Is this normal?

The oil level is good, I last changed at about 79,000km and it's synthetic. There are some leaks from the valve cover gaskets and bolts on each side, but the leaks are not that big. Can this be leading to engine problems in the long run? Should I replace the gaskets asap? The gas I'm currently using is Ultramar 94 which should be very good, though the minimum octane I can put in is 89, usually I fill up with 91 and cannot tell the difference.

I called the dealer this morning and booked an appointment early next week for the tech to diagnose the engine. I told on the phone that someone would have to listen carefully to the sound and take the car for a test drive. Just a computerized diagnostics may not reveal the problem. If they need to remove the oil pan and inspect the bearings I'm ok with that too.

The question is, do you guys think that the engine has a serious problem which is drive train related? I mean worn bearings, valves, camshaft, rods, etc.? The idea of my engine failing and needing major repair is like a nightmare for me. On the other hand, the V8 M62 engines are very reliable and running long lives, can't understand why I'm not so lucky with that one. Would like to hear some advice please.

///Greco540
02-09-2005, 01:36 PM
What you are hearing is the slapping of valves. Common on these engines. I'd get it examined. Could be oil starvation but I'm most probably wrong.

The power steering thing is also normal on the 540. with age the pump starts to lose abit of its spunk, like mine has. PS pumps are known to go now and then Could be the sign of things to come.

Valve cover oil leaks could eventually result in misfires due to oil buildup in the spark plug chamber. You should change them as soon as you can.

For the gas, I can tell the difference between Petro 91 and Shell 91. We used to have Sunoco but they are gone, and our Ultramar don't carry 94. Petro uses a methonol based additive to increase their rating to 94 but the energy content is in fact less than Shell 91. In fact Shell 91 is the highest level of energy content of all 91 gas.

I don't think the engine has a serious problem. What you are starting to experience is the repair window these cars have approaching 100K km. Once you've passed the window which includes, rad replacement, water pump replacement, rear ball joints, thrust arm bushings, and a few others you are pretty much okay for another 100K Kms.

KGB
02-09-2005, 11:26 PM
I guess, I'm not alone with this, just found another post describing similar problem:
http://maxbimmer.com/forums/showthread.php?t=40913&highlight=gasket+leak

KGB
02-10-2005, 01:23 PM
Kind of strange... this morning the knocking sound was gone, maybe, due to the cold weather or something.

I called the Ottawa dealer for an estimate to change the valve cover gaskets and possibly the screws/grommets which also leak on my engine. The labor is 1.6hrs @75bucks per hour. Each gasket is $40 and an extra $5 for the grommet.

windwagen
02-12-2005, 11:00 AM
Hi KGB, Mine was making a noise too. It sounded like a mechanical noise, but it turned out to be the "fan"belt! It went away after changing a rad hose and spilling coolant everywhere. After a while, it was making a different louder noise, and now, 35000km later, it's making a sound like what you describe, almost a tick, but barely audible. Pour a little water on it and see what happens..see if the noise comes back ..ha ha

My gaskets have been leaking like that forever. It's more damp than a leak. I'm not touching it, hovever, the quote you got is very reasonble. You could probalbly do it yourself and save some dough.

KGB
02-14-2005, 02:35 PM
Hi windwagen. I doesn't sound like a belt, belts are usually making steady whiny sounds. And this one comes not from the front but from the bottom somewhere. This one is more like "tap...tap...tap...tap" usually when the engine has warmed up a bit. I tend to agree with ///Greco540 on "valve slapping" source. I will show it to the mechanic to diagnose the engine and will post the results. Can it be transmission-related, not the engine(I still hope)? I plan to record my engine sound into a small audio clip and will post it in the forum soon.

The 1.6 hour job to replace leaky seals only covers one side, I was too optimistic to imply that it was a good deal. Replacing both gaskets would be like a $500 job. I guess, I will do it myself this summer. It's not too hard mechanically just need to be carefull disconnecting the wiring boxes and spark plug coils. Last Friday I removed the plastic spark plug covers to inspect inner leaks and it's not too bad really. The plug wells are still dry with a little bit of oil seeping through the gasket and accumulated in the near pit beside the spark plug. They are not a serious issue at this point, but need to be kept an eye once in a while.

///Greco540, I noticed a difference between Shell and other brands of gas. Shell gas, in my opinion, holds better mileage and performs better.

windwagen
02-14-2005, 10:10 PM
Hi KGB,

That's what I thought too... I never thought a belt could sound so "mechanical". So I guess the noise came back?

Good luck and please keep us posted!

KGB
03-04-2005, 03:33 PM
I recently replaced the K&N filter that was installed in that car before me with a paper one from BMW? The K&N filter was pretty dry as I could tell, like it hadn't been taken proper care of in awhile. As the filter company claims, their oiled filters give better performance and horsepower but needs cleaning and oiling once every 30,000-50,000 miles. But at the price of the engine wear????

When I removed the filter and looked through the light I could see tiny holes in it, which really scared the hell out of me. And someone including myself had been driving this car with this crappy filter for how long? As everyone knows, the gauze material used in it isn't very dense,even 4-6 layers of it can't be compared to the paper or fiber kind of filter elements. The whole idea of selling this crap is make money by duping customers into believeing in "advantages"' of increased performance, power boost and so on. The bottom line is that more dust and dirt goes through the filter and kills the engine slowly. LIke in my case it can be the exhaust valves with accumulated burn making the noise due to the large number of dirt coming through.

I would suggest that everyone who uses or considers using this product challenges the product's ability to perform as required to save yourself big engine repair cost.

windwagen
03-04-2005, 04:59 PM
I spoke to some engineers at a filter manufacturer. They did tests with filters such as the K & N, and concluded that the paper filters are more effective for filtration. In their opinions, K & N was suitable for track use only. Personally, I avoid those and CAI too.

KGB
03-06-2005, 12:25 AM
I spoke to some engineers at a filter manufacturer. They did tests with filters such as the K & N, and concluded that the paper filters are more effective for filtration. In their opinions, K & N was suitable for track use only. Personally, I avoid those and CAI too.

Exactly, that's the point. Ditch the K&N crap and install the real stuff to save your engines, folks, before it's too late.

\/\/eapon
03-07-2005, 11:29 AM
I recently replaced the K&N filter that was installed in that car before me with a paper one from BMW? The K&N filter was pretty dry as I could tell, like it hadn't been taken proper care of in awhile. As the filter company claims, their oiled filters give better performance and horsepower but needs cleaning and oiling once every 30,000-50,000 miles. But at the price of the engine wear????

When I removed the filter and looked through the light I could see tiny holes in it, which really scared the hell out of me. And someone including myself had been driving this car with this crappy filter for how long? As everyone knows, the gauze material used in it isn't very dense,even 4-6 layers of it can't be compared to the paper or fiber kind of filter elements. The whole idea of selling this crap is make money by duping customers into believeing in "advantages"' of increased performance, power boost and so on. The bottom line is that more dust and dirt goes through the filter and kills the engine slowly. LIke in my case it can be the exhaust valves with accumulated burn making the noise due to the large number of dirt coming through.

I would suggest that everyone who uses or considers using this product challenges the product's ability to perform as required to save yourself big engine repair cost.

What? you said yourself that your filter was not taken care of. Of course your going to get dirt in your engine if you filter has holes, If you clean it when it suggests 30,000 - 50,000 km it will be fine, which is far better than any paper filter.

NB Euro Direct
03-07-2005, 12:10 PM
man i have been running one of my cars without an air filter at all for about 6 months now just too see what can happen and nothing really has.
Filters are there

1)for the long run
2)for big debris

with the extreme hot temps in the chambers everything becomes smoke instantly
I have not lost compression at all
It is quite a distance from my tb to the maf and i have a flapper type which i know nothing can go wrong(if you have a wire type then you need a filter or else the maf will crap out
the heavy particles will not reach the intakes since it a long way there...

your best bet is put oil in the valve cover(head where cams are) start the car and see if it still makes the noise
might be your lifters are on the way out due to previews oil starvation or etc etc.
open your valve cover and check the clearences between lifter valve or cam valve