Compression Gremlin

shekharlele · 7th September 2009, 10:13

Hi All,

While selling my indica, I noticed a lot of mechanics pulling out the dipstick when the car was running and checking if there was oil coming out of it. The car had run 54K and was a 2004 model, engine oil and maintenance done at TASS regularly. I could also feel some oil on the finger from the dipstick.

Now, I understand this has to do with engine compression.

In my 2005 Scorpio (again regular oil changes at 10 K / 8 odd months, against recommended 15 K), I see vapours out of the dipstick (no oil at all) when the car is warm. On checking with 3 (yes, 3) Mahindra ASCs for compression testing, all said 'not required' and 'do not needlessly disturb the injectors'. Also, when I rev the engine to 1700 odd RPM, the vapours dissapear, ostensibly due to the EGR valve opening.

My questions are as follows:

1. In case of low compression, should there be other symptoms that necessarily have to co-exist with the dipstick vapour? Such as:
a. Blue smoke from exhaust
b. poor starting in the morning (does a rainy sunday night certify for a cold engine on a Monday morning?)
c. poor idling
d. Lack of torque / inability to accelerate
e. Engine oil consumption (Engine oil was checked in both cars, and no burning smell and no change in oil level / colour despite over 4 K running in stop and go traffic)
f. PUC (computerised) done at Lotus Petrol Pump - No issues found on either cars

Are the mechanics simply trying to find areas to reduce price or is there anything else I am missing?

Aside Mods - Checked for a similar thread, could'nt find it. Hence creating new one

Randhawa · 7th September 2009, 10:27

Low compression can be caused by leaking valve seals or worn out piston rings.

In that case, yes it would smoke and consume oil. Rest of the issues of starting and poor idling will follow.

Although what the mechanics are checking from the dipstick in your case is the back pressure. Which is normal for anyone to check in a engine who has a bit of mechanical knowledge to check the condition of the engine.

sgiitk · 7th September 2009, 11:22

I thought back pressure makes itself quite evident without having to pull out the dipstick. One other thing will be to check for leak of water into the sump -this is best done by dropping a a couple of drops of oil in the hot manifold. It should not crackle.

shekharlele · 7th September 2009, 11:41

Hi sgi,

I had recently given my scorp for getting the sump gasket change (there was a lsight leak) and the service centre did not report anything unusual, in fact said the oil was in a good condition.

Also, there is no vapour or oil even when I remove the oil filler cap when the engine is running. Just the dipstick....

7th September 2009, 10:13	#1
shekharlele BHPian Join Date: Dec 2006 Location: Mumbai Posts: 100 Thanked: 5 Times	Compression Gremlin Hi All, While selling my indica, I noticed a lot of mechanics pulling out the dipstick when the car was running and checking if there was oil coming out of it. The car had run 54K and was a 2004 model, engine oil and maintenance done at TASS regularly. I could also feel some oil on the finger from the dipstick. Now, I understand this has to do with engine compression. In my 2005 Scorpio (again regular oil changes at 10 K / 8 odd months, against recommended 15 K), I see vapours out of the dipstick (no oil at all) when the car is warm. On checking with 3 (yes, 3) Mahindra ASCs for compression testing, all said 'not required' and 'do not needlessly disturb the injectors'. Also, when I rev the engine to 1700 odd RPM, the vapours dissapear, ostensibly due to the EGR valve opening. My questions are as follows: 1. In case of low compression, should there be other symptoms that necessarily have to co-exist with the dipstick vapour? Such as: a. Blue smoke from exhaust b. poor starting in the morning (does a rainy sunday night certify for a cold engine on a Monday morning?) c. poor idling d. Lack of torque / inability to accelerate e. Engine oil consumption (Engine oil was checked in both cars, and no burning smell and no change in oil level / colour despite over 4 K running in stop and go traffic) f. PUC (computerised) done at Lotus Petrol Pump - No issues found on either cars Are the mechanics simply trying to find areas to reduce price or is there anything else I am missing? Aside Mods - Checked for a similar thread, could'nt find it. Hence creating new one
	() Thanks

7th September 2009, 10:27	#2
Randhawa Senior - BHPian Join Date: Oct 2007 Location: Brighton Posts: 1,192 Thanked: 355 Times	Low compression can be caused by leaking valve seals or worn out piston rings. In that case, yes it would smoke and consume oil. Rest of the issues of starting and poor idling will follow. Although what the mechanics are checking from the dipstick in your case is the back pressure. Which is normal for anyone to check in a engine who has a bit of mechanical knowledge to check the condition of the engine.
	() Thanks

7th September 2009, 11:22	#3
sgiitk BANNED Join Date: Dec 2007 Location: Gurugram Posts: 7,969 Thanked: 4,788 Times	I thought back pressure makes itself quite evident without having to pull out the dipstick. One other thing will be to check for leak of water into the sump -this is best done by dropping a a couple of drops of oil in the hot manifold. It should not crackle.
	() Thanks

7th September 2009, 11:41	#4
shekharlele BHPian Join Date: Dec 2006 Location: Mumbai Posts: 100 Thanked: 5 Times	Hi sgi, I had recently given my scorp for getting the sump gasket change (there was a lsight leak) and the service centre did not report anything unusual, in fact said the oil was in a good condition. Also, there is no vapour or oil even when I remove the oil filler cap when the engine is running. Just the dipstick....
	() Thanks