Hi,
I just bought a vacuum gauge and tested the manifold vacuum on my 1997 Volvo S40 2.0L petrol engine (normally aspirated). This engine is a 4cyl 1998ccm with 140hp and has now 335000km (208K miles).
I brought the engine to operating temp and then hooked up the vacuum gauge on a free inlet manifold port, and here are the results (in inches of Hg):
- Idle: fluctuates between 17-19"
- throttle blip: almost goes down to 0" and then up to 25" before going back to idle (17-19")
- when keeping revs around 2000rpm, I get around 20" vacuum but the reading is very steady (steadier than at idle)!
First thing to note is that my area has an elevation of about 720m (2300 feet) above sea levels. According to some websites, any elevation of 1000 feet will cause of lower reading by about 1"Hg. According to this, my engine would thus produce 19-21" vacuum at idle at sea level (which is to be compared to the usual 18-22" for a healthy engine).
So I guess my engine is still in pretty good shape after 208K miles! However I do wonder about the slightly fluctuating vacuum reading at idle which becomes steady when revs are increased. AFAIK this could be a sign of worn valve guides..... Therefore a few questions:
- Do you think that a very rapid fluctuation of about 1.5" at idle that totally disappear when reving the engine is a sign of worn valve guides or would worn valve guides produces wider fluctuations?
- I used a plastic hose to attach my gauge to the engine. This hose was fairly long and about 5mm diameter. Is this possible the fluctuation may be caused by the "excessive" width of the hose?? Do vacuum gauge normally come with a hose featuring only a very small hole in it to port vacuum??
Thanks for any comment!
I just bought a vacuum gauge and tested the manifold vacuum on my 1997 Volvo S40 2.0L petrol engine (normally aspirated). This engine is a 4cyl 1998ccm with 140hp and has now 335000km (208K miles).
I brought the engine to operating temp and then hooked up the vacuum gauge on a free inlet manifold port, and here are the results (in inches of Hg):
- Idle: fluctuates between 17-19"
- throttle blip: almost goes down to 0" and then up to 25" before going back to idle (17-19")
- when keeping revs around 2000rpm, I get around 20" vacuum but the reading is very steady (steadier than at idle)!
First thing to note is that my area has an elevation of about 720m (2300 feet) above sea levels. According to some websites, any elevation of 1000 feet will cause of lower reading by about 1"Hg. According to this, my engine would thus produce 19-21" vacuum at idle at sea level (which is to be compared to the usual 18-22" for a healthy engine).
So I guess my engine is still in pretty good shape after 208K miles! However I do wonder about the slightly fluctuating vacuum reading at idle which becomes steady when revs are increased. AFAIK this could be a sign of worn valve guides..... Therefore a few questions:
- Do you think that a very rapid fluctuation of about 1.5" at idle that totally disappear when reving the engine is a sign of worn valve guides or would worn valve guides produces wider fluctuations?
- I used a plastic hose to attach my gauge to the engine. This hose was fairly long and about 5mm diameter. Is this possible the fluctuation may be caused by the "excessive" width of the hose?? Do vacuum gauge normally come with a hose featuring only a very small hole in it to port vacuum??
Thanks for any comment!
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