I have a 2004, 3.2 DID, SWB Pajero with 320000 km on the clock. The motor is performing exceptionally well and the only recent failure I have had was with the oil pressure switch which has been renewed. Recently I noticed a new noise coming from the engine which is difficult to trace. It occurs once the engine reaches around 2500 rpm upwards and sounds as if a small fan is kicking in to add to the normal tone of the engine.
I am having the timing chain guide changed next week as a precaution and in doing so, also having the timing chain assembly checked. Perhaps some of the members have had a similar experience and can offer relevant advice. Any comment will be appreciated.
BRgds
Malcolm Bremner
Hi Malcolm,
It could be the viscous clutch on the main fan doing what it is supposed to do. Roughly this describes its operation working correctly:
1. On a cold start the fan will run at near engine speed. (You can hear the fan working over the engine sounds)
2. As soon as the engine (well, actually the sensor on the viscous clutch) warms up a little (maybe only a minute or two at 2000 - 3000 rpm operation), the fan will decouple and only spin at maybe 5-10% of engine speed. (You will hear a distinct drop off in noise from the engine compartment - you can try after starting up while stationary and be surprised at the drop in dB)
3. If the sensor on the viscous clutch reaches a high enough temperature then it will couple the fan back up and consequently the noise level will rise.
4. Once the temperature drops sufficiently the fan will partially decouple again.
The purpose is to save fuel (only have the fan work when needed) and to keep noise levels down.
But on the other hand you say it sounds like a small fan - I would not describe the sound of the main cooling fan as small.
Have you tried this with the bonnet up and a helper operating the accelerator pedal?
It could be the viscous clutch on the main fan doing what it is supposed to do. Roughly this describes its operation working correctly:
1. On a cold start the fan will run at near engine speed. (You can hear the fan working over the engine sounds)
2. As soon as the engine (well, actually the sensor on the viscous clutch) warms up a little (maybe only a minute or two at 2000 - 3000 rpm operation), the fan will decouple and only spin at maybe 5-10% of engine speed. (You will hear a distinct drop off in noise from the engine compartment - you can try after starting up while stationary and be surprised at the drop in dB)
3. If the sensor on the viscous clutch reaches a high enough temperature then it will couple the fan back up and consequently the noise level will rise.
4. Once the temperature drops sufficiently the fan will partially decouple again.
The purpose is to save fuel (only have the fan work when needed) and to keep noise levels down.
But on the other hand you say it sounds like a small fan - I would not describe the sound of the main cooling fan as small.
Have you tried this with the bonnet up and a helper operating the accelerator pedal?
Dear Andrew
Thank you for your valued input. I did check for the noise whilst the vehicle was in park by revving the motor over 2500 rpm, but there was no sign of the noise. It seems to only occur in the drive mode on acceleration and increased rpm.
Although you might be correct in suggesting that it could be coming from the main fan, my real concern is why has it only started recently - something has changed and I need to find out if it is going to become more severe and lead to a break down.
I will pass on your comment to the mechanic who is also looking into the problem for me for his information.
BRgds
Malcolm
Thank you for your valued input. I did check for the noise whilst the vehicle was in park by revving the motor over 2500 rpm, but there was no sign of the noise. It seems to only occur in the drive mode on acceleration and increased rpm.
Although you might be correct in suggesting that it could be coming from the main fan, my real concern is why has it only started recently - something has changed and I need to find out if it is going to become more severe and lead to a break down.
I will pass on your comment to the mechanic who is also looking into the problem for me for his information.
BRgds
Malcolm
If it is the fan, then it could be a symptom of something else. i.e. the engine is running hotter (not related to the fan) and hence the fan is having to work (engage) more often.
Have you made any changes recently like chipped the vehicle, added bigger tyres, etc?
Have you made any changes recently like chipped the vehicle, added bigger tyres, etc?
No, nothing has been deliberately changed at all. Travelled to Moz over Christmas and did some travel over sandy roads in very hot conditions, but no show of any temperature change on the dashboard indicator then or now.
Malcolm,
Maybe I didn't phrase that too well. What I was trying to convey:
If it is the fan, then it could be a symptom of something else. i.e. the engine is generating more heat and hence the fan is having to work (engage) more often to maintain the correct temperature.
Anyway, lets see what your Mech discovers.
Maybe I didn't phrase that too well. What I was trying to convey:
If it is the fan, then it could be a symptom of something else. i.e. the engine is generating more heat and hence the fan is having to work (engage) more often to maintain the correct temperature.
Anyway, lets see what your Mech discovers.
Thank you, Andrew. I will take your advice into consideration and check on this where possible. I will also let you know if we manage to clearly identify it and sort it out.
I had the timing chain guide replaced today and even if it is not related to the engine noise I am trying to identify, I am very lucky that I did. Have a look at it and see just how lucky I was !!!
Attachments:
Mmmm I would say it was due for replacement earlier!Malcolm wrote:I had the timing chain guide replaced today and even if it is not related to the engine noise I am trying to identify, I am very lucky that I did. Have a look at it and see just how lucky I was !!!
What would be of concern is where are all the chunks of the nylon (?) block? You wouldn't want them running around the engine.
Probably either dissolved due to wear or drained out with the old oil during the routine services.