General Strange Noise when Idle

[Harish602]

I had replaced the Drive shafts, front suspension, track control arm for my 11 years old UNO 1.7D due to normal wear (the roads are not too good at Mumbai). Also the reverse gear were not engaging. The mechanic had to remove the transmission and the gear box to fix the reverse gear problem which was due to the gear selector engagement lever in the transmission getting stuck.

The mechanic set right all the problems, but i am noticing a lot of vibration and noise from under the transmission when the car is not moving after i did a test run after the repairs. The vibration and noise somewhat reduces when i drive the car but is more when stationary. Also the vibration and noise increases when i turn the AC ON.

The mechanic have not yet done wheel balancing after the drive shaft and front suspension replacement and will do when the noise/ vibration problem is sorted out. Also i have also replaced the right site rear bearing which was worn.

Can anyone pinpoint the noise and vibration problem and where to start looking from.

Thanks in advance,

Best Regards,

Harish.

 

[alexGS]

Hello Harish, welcome :wave:

I'm sorry that no-one's replied yet - possibly due to the 1.7D model being really unusual in most countries. I've never seen one either but two points come to mind.

Try to watch various parts such as the air conditioning compressor when you have someone disengage/engage the A/C. Perhaps some of the mounting bolts are loose?

Also, check that the exhaust brackets are tight - I think there is a bracket that stabilises the exhaust pipe where it bends to run underneath the car. Then check that the rubber hangers are keeping the pipe from touching the car body. It could be that the small change in idle speed when the A/C comes on is sufficient to create a rattle.

Diesel engines by their very nature create far more vibration than petrol engines, due to the high compression required to run them and therefore the heavier rotating/reciprocating parts.

-Alex

 

[[email protected]]

Hi,
Check the top and bottom( near gearbox ) engine mounts, the rubber may have worn out and the lower mount may be touching the body. As suggested by Alex check for any loose nuts. beside do you change the timming belts? it seems that when one puts new belts the overall noice at idle speed increase until the belt gets set.

(men at workshop will usually use jack to lift the engine slightly with out loosening the mount bolts, this will easly get damaged if not.)

 

[Harish602]

Thanks everybody for your valuable replies. The top front mounting had some play which was causing the vibration of the engine. Replaced the mounting which reduced the vibration by 50%. Also the mechanic did some door panel tightening and overall nuts/bolts tightening which reduced the noise and vibration by another 20%. Still it is not as good as factory fitting. Also checked the exhaust pipe which is okay.

Can a new drive-shaft and track control arm cause any vibration / noise if they are new?

Added some additives today for the car which will help clear any blocked injectors (the one which you add along with the diesel). Hope to help increase pick-up and power.

Thanks once again.

Harish.

Hi,
Check the top and bottom( near gearbox ) engine mounts, the rubber may have worn out and the lower mount may be touching the body. As suggested by Alex check for any loose nuts. beside do you change the timming belts? it seems that when one puts new belts the overall noice at idle speed increase until the belt gets set.

(men at workshop will usually use jack to lift the engine slightly with out loosening the mount bolts, this will easly get damaged if not.)

 

[eby]

Have you replaced transmission mountings ?. Nylon mountings last longer than rubber ones. New drive shaft and track control arms don't cause any vibration.

If you are concerned with noise, you should consider using noise deafening products inside your car, as the original materials deteriorate(carpets, that silver heat/noise material inside the engine bay, foam+cotton waste material inside the cabin, etc..).

 

[Harish602]

Did not replace the Transmission mounting but only the rubber front mounting of the engine.

Are you suggesting damping of the noise using foam + cotton waste inside the cabin? Are they not risky considering the heat generated inside the Bonnet?

Will check with the mechanic for the transmission mouting option you suggested.

Thanks for your valuable suggestions.

Best Regards,
Harish.

Have you replaced transmission mountings ?. Nylon mountings last longer than rubber ones. New drive shaft and track control arms don't cause any vibration.

If you are concerned with noise, you should consider using noise deafening products inside your car, as the original materials deteriorate(carpets, that silver heat/noise material inside the engine bay, foam+cotton waste material inside the cabin, etc..).

 

[alexGS]

Yes, plenty of option for boosting the soundproofing of an Uno, though I imagine the diesel model comes with a bit more soundproofing than standard.

It's best to eliminate vibration at source first - checking the other mountings is a good idea. The track control arm bushes are unlikely to relate to engine vibration.

You are right about adding soundproofing to the bonnet - you have to be a bit careful there as the heat causes the adhesive to fall off - but if you add soundproofing inside the car, you will be fine. Perhaps see what is there already and consider adding more similar material.

You will find that there are several types of soundproofing material:

• a bitumen-like sheet about 3mm thick stuck to the metal to reduce the vibration of the metal itself (called damping material),
  
• then a much thicker layer of 'cotton waste' (chopped-up clothes made into a blanket, which you can buy as 'mover's blanket' used for furniture removal),
  
• and finally another layer of bitumen sheet which often breaks up due to the flexibility of the cotton waste.

This final layer is very important - it creates a 'sandwich' so that the sound waves are reflected back into the soft material, and therefore, dissipated.

The bulkhead (firewall) soundproofing has a better-quality top layer to enhance its effectiveness. If you improve the rest of the flooring to match the bulkhead, seal up holes in the inside sills and pillars, and add damping material (sheets) to the doors, especially to cover the holes in the door metalwork prior to fitting the trim card, you'll notice the improvement.

Unfortunately soundproofing is something that has to be tackled very comprehensively - as the sound will 'seek out' the chink in the armour - something like a missing grommet for the speedometer cable can undo much of the good work!

-Alex

 

[Harish602]

Thanks Alex for all your valuable suggestions to remove noise inside the cabin and from the Bonnet. I will consider all of your suggestions one by one and see what i can implement. Since implementing them will take some time in analyzing the issue, and then see if the noise goes down, will not be able to reply immediately until finished.

Thanks once again for the suggestions.

Best Regards,

Hari.

Yes, plenty of option for boosting the soundproofing of an Uno, though I imagine the diesel model comes with a bit more soundproofing than standard.

It's best to eliminate vibration at source first - checking the other mountings is a good idea. The track control arm bushes are unlikely to relate to engine vibration.

You are right about adding soundproofing to the bonnet - you have to be a bit careful there as the heat causes the adhesive to fall off - but if you add soundproofing inside the car, you will be fine. Perhaps see what is there already and consider adding more similar material.

You will find that there are several types of soundproofing material:

• a bitumen-like sheet about 3mm thick stuck to the metal to reduce the vibration of the metal itself (called damping material),
  
• then a much thicker layer of 'cotton waste' (chopped-up clothes made into a blanket, which you can buy as 'mover's blanket' used for furniture removal),
  
• and finally another layer of bitumen sheet which often breaks up due to the flexibility of the cotton waste.

This final layer is very important - it creates a 'sandwich' so that the sound waves are reflected back into the soft material, and therefore, dissipated.

The bulkhead (firewall) soundproofing has a better-quality top layer to enhance its effectiveness. If you improve the rest of the flooring to match the bulkhead, seal up holes in the inside sills and pillars, and add damping material (sheets) to the doors, especially to cover the holes in the door metalwork prior to fitting the trim card, you'll notice the improvement.

Unfortunately soundproofing is something that has to be tackled very comprehensively - as the sound will 'seek out' the chink in the armour - something like a missing grommet for the speedometer cable can undo much of the good work!

-Alex

 

[eby]

Did not replace the Transmission mounting but only the rubber front mounting of the engine.

Hope you meant the entire hydraulic mount(not just the rubber washer inside as many would do to save money), pic 1.

Are you suggesting damping of the noise using foam + cotton waste inside the cabin? Are they not risky considering the heat generated inside the Bonnet?

The noise/heat damping materials came with the vehicles are heat&fire retardant, as they're not ordinary foam+cotton waste. pic 2&3.

As Alex suggested, only use commercial noise/vibration/heat dampening materials available for the automotive industry. If you are interested in installing these in your vehicle, do let me know as i'm in the hunt for such materials in this country. "Second Skin" products are the best according to many auto buffs.