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Noise from the engine compartment

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Lutz Kramer

Lutz Kramer

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Hallo from Germany,

last week a noise started to come from the engine compartment of my AH 3000 Mk III BJ8. This noise has a very high frequency and sounds like a turbine. It goes up with the rev of the engine. It’s no knocking or clacking or rattling!

What I’ve done so far is:
- rocker clearance checked --> OK
- compression on all 6 Zyl. is the same --> OK
- took the distributer out and checked for noises --> OK
- took the fan belt off, to make sure it’s not coming from the water pump or generator
- when depressing the clutch, the noise is still there!
- I tried to find the source with a statoscope and believe the sound is coming from the front end of the engine

My guess is, it could be
- a camshaft bearing or
- main shaft bearing
- missing rubber surface of the tensioner or the chain damper, so the chain runs on the metal surface of those two parts

Hopefully it’s the last guess, because otherwise I have to disassemble the engine.

I have to add the fact, that I did an overhaul on the transmission just 2 weeks ago. But I don’t think the noise is coming anywhere from the gear box, OD or first motion shaft, since the noise is not affected, when I depress the clutch which of course disengages the first motion shaft from the crank shaft.

May be anybody has already encountered a similar problem or has an idea, what the cause may be.

Thank you all!
Lutz
 
I agree with Marvin, remove V-belt & start engine & see if noise is gone. Also spin W/P & generator by hand, sometimes brushes or brgs can make similar noise. cheers
 
Based on what you've already checked, I'm thinking it has to do with the timing chain. I don't think the camshaft or main bearings would make that sound.
 
Item Four on his initial list of things he's tried is removed the belt.
NO clacking or rattling...sounds like a turbine.
Could be chain gone against the side of the timing cover.
Or something really silly like a branch stuck up under the car rubbing on the backside of the damper.
 
Hi John,

I agree with you and hope it's not the bearings. I also do believe it has something to do with the timing chain.

This leads me to the question, if the oil pressure would be affected if one of the main bearings would have been scratched? Since my oil pressure ist still OK, the bearings could then be eliminated as a cause factor.
 
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TOC,

if the chain would slide along the timing cover it probably could create a noise like the one that bothers me.
 
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What if one of the camshaft or crankshaft bearings would be bad, could this create a noise like the one I described in #1 and would this result in a drop of oil pressure?
 
Bad timing chain tensioner ??
 
Hi Lutz,

If the problem is with the timing chain, I would expect the tensioner foot would have escaped its cylinder and oil pressure would be lower then previous at speed. If oil pressure has not changed, I would expect the foot to be in place and pressing against the chain and the chain. If this is so, I would conclude the chain must also be in place and not the problem. It should be noted that the oil pressure fall would not be great as oil would be freely flowing through a small orifice. but. the pressure fall should be noticeable. That being said, your noise could be still caused in that area but not as suggested by others.
Just a thought,
Ray (64BJ8P1)
 
Hello Lutz,

for my understanding the high frequent noise should not come in my opinion from the chain.
This is more a ratteling .
But anyway, I did not hear the noise.
At my engine rebuild the tensioner rubber was completly destroyed and the hydraulic system behind the tensioner to support the press on force was worn out. This cause no high frequent noises. Nevertheless I would try it with a new tensioner to exklusive a chain issue.

About your suggestion of the bearings. I would try to "oil" from the outside to check the noise will be change (only to check something will change)

Also an idea : Do you sure that with the assembly of the gear everything is well done ? Is it possible that something on the mainshaft will press the crankshaft in direction to the front of the engine ?

Viel Glück (Good luck)
 
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Hello Lutz, the noise that you describe sounds like the starter motor has failed to disengage after starting. I had exactly the same problem, a whirring noise that got higher as the revs increased. I hope this helps.

Will
 
Good thinking Will,

I totally forgot that, although in another car, I too had the same issue and sound was as described. If that is the problem, I would also expect the starter would turn from a motor to another generator and push additional current into the electrical system. I would suggest measuring the current and voltage and if higher then appropriate, would validate the diagnosis.

It is so good to have such a diverse participation to brake the potential herding tendency.

Good luck,
Ray (64BJ8P1)
 
I think germanmichel is right, because in most cases a problem with the chain and tensioner should result in a rattling noise and not in a sound like a turbine. But how can you "oil" camshaft bearings from the outside?

By the way, it's definitely not the starter. Since the noise lasts now for more than 300 Miles. I'm sure the starter would have been destroyed already if it would have been driven by the engine at high rpm.

Another good idea mentioned by germanmichel is, that probably something on the mainshaft might press the crankshaft in direction to the front of the engine, since I had assembled the gear box short before the noise started. But I don't have any idea what could cause the inputshaft to be moved towards the crankshaft. That could only be the case, if the first motion shaft (inputshaft) that ist freely connected with the third motion shaft (outputschaft) would be forced so by the latter shaft. But hardly to believe.

I guess, I already know what I have to do during the winter period. I'll lift out the engine together with the gearbox and OD and run the engine without the gear box on a test stand and then go from there on. But before I do that, I first will take a look behind the timing cover, because you never know.
 
How about a broken crankshaft oil slinger ? . the one behind the timing cover
 
Hello Lutz ,

i want not have really right, there are only advices to bordering the root cause.


But how can you "oil" camshaft bearings from the outside?

Click to expand...
Clear I mean the crankshaft only between pulley and oil seal. You never reach the bearing also on the crankshaft .

So for me it sounds like you are still on analyse the root cause...
I have no additional ideas, except the experience that if I change anything and after that something is different, it has normally a connection to the change....

Bye Michael
 
You can run the engine in place without the gearbox, if it comes to that. Leave the engine in place with a strong bar across the frame at the rear of the engine.
Be careful, of course.
 
To leave the engine in place is quite a good idea! I know, in that case you have to support the engine, which you have to do anyhow when you pull the trans.
 
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