Please enable JavaScript to get all features available.
Search in Gari.pk
Login Post Ad

Need Info!!

Need Info!!

Assalam-o-Alaikum:-
Mai nai bahad say logon ko dekha hai k jab wo gari buy kar rhay hotay hain tu wo head ka oil cap open kartay hain jahan say oil daltay hain engine mai. Aur full race daytay hain.
mara sawal yay hai k
Engine head ka oil cap open kar k full race daynay say kia pata chalta hai???
Gari.pk User 616 asked on 16 Jun 2010 14:19:02 pm
1 Answer
362 views |
Arham - on 16 Jun 2010 14:19:33 pm
When the piston goes up (in compression stroke), there is blow-by from cylinder sleeve and valve seals. In most modern engines (read: from the past 50 years) there is blow-by return. In the blow-by return system, a pipe runs from tappet cover to air filter housing. This way the blown-by gases are recirculated through the ignition system and emissions are reduced. Moreover, there is a by-pass through which the blow-by occurring from cylinder sleeve is also directed to the tappet cover.

A side advantage is you can have a sealed sump, otherwise blow-by gases increase internal pressure and you'd need a PCV (pressure check valve) in the sump, thus decreasing fording ability.

Anyhow, people open the oil cap to see whether smoke/fume is coming out in an appreciable volume, which would mean the engine is losing compression (either from cylinder sleeve or from valve seals). Higher the RPM, higher the pressure loss (that may also explain why very old engines lose power on revving and run better on low RPMs). However, this is not the correct/consistent method b/c it does not give you a numerical value. Remember for technical purposes you always need a numerical value, not a subjective value. The correct method is to install a pressure gauge in the spark plug socket and then start the engine. If the pressure is within threshold mentioned in the service manual, its OK, otherwise not.

Note: Some engines despite having a chamber blow-by recirculate, still have a PCV.
 

Related Topics

User Also Viewed