What happens to the engine oil when the Oil cap and/or dipstick is opened?

r@CYR@y · 10th November 2009, 18:32

Quote:

Originally Posted by bblost

Engine oil can and does reach a high temperature.
I learnt this the hard way.

My old bike, a HH Splendour needed an oil change.
I went to the nearby store. They were out of stock. So I ended up riding close to 5 kms before getting the oil and returning home.

Right away sat down, put on my cotton gloves with rubber grips.
Long story behind the gloves. Have 8 stitches on my finger before my Dad made them mandatory.

So I opened the nut under the engine cover. HOT oil all over my hand.

Lesson learn't.

Well yes, Me too a little similar but with the car oil (I was very lucky that day), There is a lot of oil in a car (Compared to a bike and positioning too) and the pressure can be huge inside even after a short ride..

The engine temperature play a very important role here and the weather too, Even if you try to open the cap after covering a small distance depending on the temp either oil cap may blow out with sudden release of gas or nothing will happen..

Jaggu · 10th November 2009, 18:43

Never do such things when engine is warmed up. If you really wanna take a peak, do it when engine is cold. Better still open the cap and then peek, ideally wear a glass or keep safe distance to save your eyes from splash.

But i dont see any point doing all this, coz hardly any major part will be seen through these oil filler holes, which can let you know if all is well.

r@CYR@y · 10th November 2009, 18:46

Quote:

Originally Posted by D.V.R

@bblost-sorry to hear that mate,but dont we learn it the hard way.

I am not intrested in opening the engine oil drain valve under the engine but the engine oil filling cap on top of the engine.

I was talking about the oil filling cap on the top of the engine..
Nobody is going to open the drain cap cap with the engine running, It will destroy the engine parts due to lack of lubrication..

Keep revving..

D.V.R · 10th November 2009, 18:48

Ok thanks all for the replies,I wont venture near this topic in respect to the safety hazards present.

MODS-The purpose of the thread has been served you can close it.

Raccoon · 10th November 2009, 19:51

Quote:

Originally Posted by bblost

Engine oil can and does reach a high temperature.
I learnt this the hard way.

My old bike, a HH Splendour needed an oil change.
I went to the nearby store. They were out of stock. So I ended up riding close to 5 kms before getting the oil and returning home.

Right away sat down, put on my cotton gloves with rubber grips.
Long story behind the gloves. Have 8 stitches on my finger before my Dad made them mandatory.

So I opened the nut under the engine cover. HOT oil all over my hand.

Lesson learn't.

But how come you did not/could not estimate the temp. of the oil by just touching the crankcase or for that matter the drain bolt itself?? I have always drained oil on a hot engine, as that is how it should be done... and have never got burns.... as its easy to estimate how how the oil might be.

bblost · 10th November 2009, 21:08

Racoon. I did this in 1999. Almost a decade back. It was a very stupid thing to do.

The gloves saved me from any serious burn as I managed to remove them before injury.
This was the second time I was doing an oil change.

The first time I ended with 8 stitches on my finger as my spanner slipped.

But this is going way OT. Lets drop it at that. These stupid things now sound so funny. But should serve as a warning to anyone who tries stuff on their own.
The risk of injury is very real.

Be careful and wear protective gear always.

ph03n!x · 10th November 2009, 22:24

The point of this thread, I presume, is to judge an engine's condition. I vaguely remember my dad telling about 5 years back that if you open the oil filler cap, shut the hood, start the car and give throttle- if oil splashes out of the oil filler, then the engine is bad.

Not sure how correct or true this is...

D.V.R · 10th November 2009, 22:31

Quote:

The point of this thread, I presume, is to judge an engine's condition. I vaguely remember my dad telling about 5 years back that if you open the oil filler cap, shut the hood, start the car and give throttle- if oil splashes out of the oil filler, then the engine is bad.

This is what made me start this thread.

VANOS · 14th December 2009, 01:57

ok guys here's the real deal,
if you have an ohc the chances of oil soming out of the valve door cover cap ie the engine oil cap is quite high unless it has a cover plate to prevent it. as far as diesel engines are concerned it is more likely due to the higher compression ratio, a little blow by is allowed. but if your dip stick is removed and oil is leaking through the top of it, you got to replace the piston rings. worst case is your cylinder walls are damaged and it's time for an overhaul.

Note from the Team-BHP Support Team : Please take the time to use proper punctuation as per Team-BHP rules. Thanks!

chaudh2s · 12th March 2014, 18:06

Well, i don't think there would be any problem, if the oil cap or dip stick is opened in an idling engine. I can say so with confidence because, when you take your Diesel engined car to any used car dealer for evaluation, the first thing they do to evaluate health of engine is, open the oil cap and dip stick with engine running to check back pressure (that was the term used if i remember correctly). It was done for my MJD punto and there was no oil coming out.

narendra.vw · 12th March 2014, 19:32

There will no pressure inside valve door cover. Remember Valve door cover has Breather pipe to relive vacuum inside valve door cover. No pressure like radiator cap. Some car’s valve door have a plate so that oil does not spill out. If cap is kept open & run for few km Engine may run out of oil & siege.
We open the cap just to check circulation. If oil is hot , max you may burn your skin.
Regarding checking Engine life, If white smoke seen through valve door or Dip stick hole, then engine needs rebuild.

jaguar.runs · 12th March 2014, 20:51

If you open the cap on the valve cover, engine idling will be erratic. I have seen this on my car when I had added some additive. Nothing will happen with the dipstick removed as the mechanics normally check the oil level while the engine is idling.

narendra.vw · 13th March 2014, 20:00

jagar.runs,
My experience with following Engines,
1.Petrol:-- carb, mpfi. 2.Diesel:-- Mechanical pump(In line & Rotary type), crdi, TD & lastly TDI.

Yours is the first issue that I have not come across before. Please let me know the car & the engine which you are referring to.
Regarding Additive,
Most Important:--Oil has to be new & warmed up before adding Additive . It takes a while for Additive to mix with the Cold oil. This may have caused the erratic idling.
Remember Oil Viscosity is thinner when Hot & mixes well with Additive.
Once Additive is added I strongly recommend to keep engine running for 15 min or be Driven 50 km min keeping constant speed. Cap closed

A bit of flash back.
Valve tappet gap of old Petrol Fiat & Ambassador engine were adjusted while engine running with Valve door removed & Oil reaching operating Temp.
Present Engines come with self adjusting hydraulic tappet Cups .

jaguar.runs · 9th April 2014, 16:12

Quote:

Originally Posted by narendra.vw

jagar.runs,
My experience with following Engines,
1.Petrol:-- carb, mpfi. 2.Diesel:-- Mechanical pump(In line & Rotary type), crdi, TD & lastly TDI.

Yours is the first issue that I have not come across before. Please let me know the car & the engine which you are referring to.
Regarding Additive,
Most Important:--Oil has to be new & warmed up before adding Additive . It takes a while for Additive to mix with the Cold oil. This may have caused the erratic idling.
Remember Oil Viscosity is thinner when Hot & mixes well with Additive.
Once Additive is added I strongly recommend to keep engine running for 15 min or be Driven 50 km min keeping constant speed. Cap closed

A bit of flash back.
Valve tappet gap of old Petrol Fiat & Ambassador engine were adjusted while engine running with Valve door removed & Oil reaching operating Temp.
Present Engines come with self adjusting hydraulic tappet Cups .

Sorry, missed out your post. Mine is a Mitsubishi Lancer with 4B11 engine. I put in the additive only after engine was warm enough, had just returned from a drive which means it would have reached the optimum operating temperature. When I noticed the erratic idling, I had asked my brother who is Automobile Engineer if it is normal. He confirmed that it is and he has seen this previously with other engines also. We had followed the product instruction & kept the engine idling for more than 10 minutes after pouring in the additive.

rajivanoj · 19th September 2016, 17:35

I have also same doubt. The scenarios are

1) I had opened the dip stick , with oil filler cap closed, there was no oil spillage from dip stick. but there was air coming out.

2) I had opened the oil filler car too, with dip stick. The oil spits out from the dip stick

Both the conditions have idle engine, car is lancer diesel. Is this sign of bad engine?

10th November 2009, 18:43	#17
Jaggu Team-BHP Support Join Date: May 2004 Location: Bangalore Posts: 20,383 Thanked: 17,293 Times	Never do such things when engine is warmed up. If you really wanna take a peak, do it when engine is cold. Better still open the cap and then peek, ideally wear a glass or keep safe distance to save your eyes from splash. But i dont see any point doing all this, coz hardly any major part will be seen through these oil filler holes, which can let you know if all is well.
	() Thanks

10th November 2009, 18:48	#19
D.V.R BHPian Join Date: Jul 2006 Location: Sydney / Secunderabad Posts: 277 Thanked: 14 Times	Ok thanks all for the replies,I wont venture near this topic in respect to the safety hazards present. MODS-The purpose of the thread has been served you can close it.
	() Thanks

10th November 2009, 21:08	#21
bblost Team-BHP Support Join Date: Jul 2007 Location: Hyderabad Posts: 11,284 Thanked: 17,945 Times View My Garage	Racoon. I did this in 1999. Almost a decade back. It was a very stupid thing to do. The gloves saved me from any serious burn as I managed to remove them before injury. This was the second time I was doing an oil change. The first time I ended with 8 stitches on my finger as my spanner slipped. But this is going way OT. Lets drop it at that. These stupid things now sound so funny. But should serve as a warning to anyone who tries stuff on their own. The risk of injury is very real. Be careful and wear protective gear always.
	() Thanks

10th November 2009, 22:24	#22
ph03n!x Senior - BHPian Join Date: Jun 2008 Location: Coimbatore Posts: 2,602 Thanked: 6,158 Times	The point of this thread, I presume, is to judge an engine's condition. I vaguely remember my dad telling about 5 years back that if you open the oil filler cap, shut the hood, start the car and give throttle- if oil splashes out of the oil filler, then the engine is bad. Not sure how correct or true this is...
	() Thanks

14th December 2009, 01:57	#24
VANOS BHPian Join Date: Apr 2006 Location: Chennai Posts: 52 Thanked: 20 Times	ok guys here's the real deal, if you have an ohc the chances of oil soming out of the valve door cover cap ie the engine oil cap is quite high unless it has a cover plate to prevent it. as far as diesel engines are concerned it is more likely due to the higher compression ratio, a little blow by is allowed. but if your dip stick is removed and oil is leaking through the top of it, you got to replace the piston rings. worst case is your cylinder walls are damaged and it's time for an overhaul. Note from the Team-BHP Support Team : Please take the time to use proper punctuation as per Team-BHP rules. Thanks! Last edited by aah78 : 14th December 2009 at 05:27. Reason: Note added.
	() Thanks

12th March 2014, 18:06	#25
chaudh2s BANNED Join Date: Jul 2010 Location: Gurgaon Posts: 388 Thanked: 822 Times	Re: What happens to the engine oil when the Oil cap and/or dipstick is opened? Well, i don't think there would be any problem, if the oil cap or dip stick is opened in an idling engine. I can say so with confidence because, when you take your Diesel engined car to any used car dealer for evaluation, the first thing they do to evaluate health of engine is, open the oil cap and dip stick with engine running to check back pressure (that was the term used if i remember correctly). It was done for my MJD punto and there was no oil coming out.
	() Thanks

12th March 2014, 19:32	#26
narendra.vw BHPian Join Date: Apr 2010 Location: Bangaloru Posts: 293 Thanked: 425 Times	Re: What happens to the engine oil when the Oil cap and/or dipstick is opened? There will no pressure inside valve door cover. Remember Valve door cover has Breather pipe to relive vacuum inside valve door cover. No pressure like radiator cap. Some car’s valve door have a plate so that oil does not spill out. If cap is kept open & run for few km Engine may run out of oil & siege. We open the cap just to check circulation. If oil is hot , max you may burn your skin. Regarding checking Engine life, If white smoke seen through valve door or Dip stick hole, then engine needs rebuild.
	() Thanks

12th March 2014, 20:51	#27
jaguar.runs BHPian Join Date: Jan 2010 Location: Dubai Posts: 277 Thanked: 105 Times View My Garage	Re: What happens to the engine oil when the Oil cap and/or dipstick is opened? If you open the cap on the valve cover, engine idling will be erratic. I have seen this on my car when I had added some additive. Nothing will happen with the dipstick removed as the mechanics normally check the oil level while the engine is idling.
	() Thanks

13th March 2014, 20:00	#28
narendra.vw BHPian Join Date: Apr 2010 Location: Bangaloru Posts: 293 Thanked: 425 Times	Re: What happens to the engine oil when the Oil cap and/or dipstick is opened? jagar.runs, My experience with following Engines, 1.Petrol:-- carb, mpfi. 2.Diesel:-- Mechanical pump(In line & Rotary type), crdi, TD & lastly TDI. Yours is the first issue that I have not come across before. Please let me know the car & the engine which you are referring to. Regarding Additive, Most Important:--Oil has to be new & warmed up before adding Additive . It takes a while for Additive to mix with the Cold oil. This may have caused the erratic idling. Remember Oil Viscosity is thinner when Hot & mixes well with Additive. Once Additive is added I strongly recommend to keep engine running for 15 min or be Driven 50 km min keeping constant speed. Cap closed A bit of flash back. Valve tappet gap of old Petrol Fiat & Ambassador engine were adjusted while engine running with Valve door removed & Oil reaching operating Temp. Present Engines come with self adjusting hydraulic tappet Cups .
	() Thanks

19th September 2016, 17:35	#30
rajivanoj BANNED Join Date: Mar 2007 Location: Coimbatore Posts: 398 Thanked: 52 Times View My Garage	Re: What happens to the engine oil when the Oil cap and/or dipstick is opened? I have also same doubt. The scenarios are 1) I had opened the dip stick , with oil filler cap closed, there was no oil spillage from dip stick. but there was air coming out. 2) I had opened the oil filler car too, with dip stick. The oil spits out from the dip stick Both the conditions have idle engine, car is lancer diesel. Is this sign of bad engine?
	() Thanks