720 4x4 Loud Screeching

[Dan.]

Greeting,

 

I have a 1984 720 4x4,  it has developed a very loud screech and I am having difficulty locating it. The screech occurs when raising the RPMS and then dropping the peddle rapidly, or when at about 2nd to 3rd gear under load. It is a full time screech when it is occurring. I have not replaced either of the two belts because they were done less than 4000 miles ago. My big question is, can the timing chain make such a screech? The sound is like an old pencil sharpener that needs to be lubed up, but ofcourse extremely louder. I sprayed WD40 on both belts and it did not mitigate the sound. I also believe the sound is coming from the lower front of the engine. I mainly ask if this is possible for the timing chain to make such a screech? Much thanks for any support on the matter.

 

Dan.

[datzenmike]

No. Just like bicycle chain on sprockets, can't slip.

 

Oiling the belts is not a good idea as it will cause slippage and squealing. Check that they are tight they can stretch when new.  Use thumb, push on belt half way between alternator and fan pulley. Should only move 1/2" Same with power steering belt. I've had a loose belt and can only describe it as a very loud shriek.

 

 

Check your engine oil level.

Check power steering fluid level.

Does the clutch fan turn by hand smoothly?

 

[Joecar]

58 minutes ago, Dan. said:

Greeting,

 

I have a 1984 720 4x4,  it has developed a very loud screech and I am having difficulty locating it. The screech occurs when raising the RPMS and then dropping the peddle rapidly, or when at about 2nd to 3rd gear under load. It is a full time screech when it is occurring. I have not replaced either of the two belts because they were done less than 4000 miles ago. My big question is, can the timing chain make such a screech? The sound is like an old pencil sharpener that needs to be lubed up, but ofcourse extremely louder. I sprayed WD40 on both belts and it did not mitigate the sound. I also believe the sound is coming from the lower front of the engine. I mainly ask if this is possible for the timing chain to make such a screech? Much thanks for any support on the matter.

 

Dan.

Mine also does this too when i shift into first gear and give it some gas but that goes away after like a few minutes

 

[datzenmike]

You can buy spray belt dressing for squeals but the belt must be adjusted properly first.

 

Another possibility is a bad bearing in the alternator, water pump or power steering pump. If the lower front of the engine then maybe the alternator.

[thisismatt]

Fan clutch?

[weldingrod]

I think you are right, Mike, v belt. After a new alternator belt install, several weeks later I could hear a slipping belt when I started up. I always hit my lights right after starting and when I turned the lights of the squealing stopped. Instant diagnosis. Nice the D21 has an adjustor on each belt. I know the earlier ones use the same block so my question is this: are the tapped holes already in place to put individual belt tensioners on, say, a 1984 720?

[datzenmike]

I doubt it. The Z is the same as the L series.

 

The alternator adjusts the fan belt and the power steering and air con have their own separate adjustable pulley tensioner

[datzenmike]

2 hours ago, thisismatt said:

Fan clutch?

 

I mentioned checking if it turns smoothly. If it was fully seized the fan turns same speed as the pulley and roars like a jet taking off. All in all I think it's a fan belt. They are LOUD. I've spun SBC rod bearings and they are not that loud.

 

 

[Thomas Perkins]

Get your crow bar and tighten your alternator.

[Stoffregen Motorsports]

On 10/11/2022 at 9:08 AM, Thomas Perkins said:

Get your crow bar and tighten your alternator.

Just be sure you have both alignment pins in the water pump, or you'll be hearing another screech from inside the water pump cavity. 😁

[datzenmike]

 

 

Dan. has llllllleft the building...

[Thomas Perkins]

I had a loud screeching before.The noise echoed.I knew it wasn't any belts.It was the yoke...

[Thomas Perkins]

3 hours ago, Stoffregen Motorsports said:

Just be sure you have both alignment pins in the water pump, or you'll be hearing another screech from inside the water pump cavity. 😁

Mine was missing one pin but it didn't make a noise,but it did grind the metal inside,I believe the pump was still good,but I replaced it anyway cause it was free and had it all apart,radiator and everything else.

[Dan.]

Hello. I left the building but I am back two years later, oops. It ended up being the darn belt had some oil on it due to power steering pump leaking. Replaced belt and rebuilt power steering pump and she turns like a dream! I contacted Weber to check price on the Carb conversion, I will probably do a Carb upgrade sometime in near future.