14 replies to this topic

[Clubby1275GT]

Was talking to a mate the other day who used to have a modified mini, used to play with subaru's, bit of an ace at the wheel mind.

anyhow he was saying that i should have a breather hole in my rocker cover, cant remember the reason why but he said he swore by having one

i noticed that some old rocker covers used to have breathe pipes on them but the newer cars tended to not


can anyone shed any light on this for me?? pro's and con's of them??

Cheers

Daz

[Garagiste]

General concensus seems to be that it helps prevent the oil emulsifying under the cover if the car is used only for short journeys.
I still have the original type that bears the joke (IIRC): "replace every six months"
Has anybody ever done so? I did replace mine once - with one from a Metro at the scrappy - but only because I drove off after I changed my oil and lost the old one.

[Jimmyarm]

Dont know about the 1275's but if you leave the filler cap off a 998 it runs like a bag of poo (something to do with crankcase pressure ?).

Surely adding a hole into the rocker cover will have the same effect ?

[Garagiste]

Oh, I see - you're actually talking about the cover itself - my brain inserted a "cap" where there wasn't one!
Maybe it's for if your cap itself isn't vented?

[biggav]

General concensus seems to be that it helps prevent the oil emulsifying under the cover if the car is used only for short journeys.
I still have the original type that bears the joke (IIRC): "replace every six months"
Has anybody ever done so? I did replace mine once - with one from a Metro at the scrappy - but only because I drove off after I changed my oil and lost the old one.

is this why i have mayonaise in my rockers???? changed 3 faultless head gaskets (and 1 very blown one along with the head) and done engine flush and oil change twice.... still emulsified and only do infrequent short journeys.

[The Matt]

I will be adding breather pipes onto my rocker cover, well, tey'll be outlets to a catch tank really, but it's not the same circuit as the original breather system because I have no air filter housing, just a pair of filter socks on trumpets.

Anyway, people sometimes just slap a breather filter on the outlet from the crank breathers (when using K&Ns etc.)

@ Gav, if you are only ever doing short journeys, that'll probably be the main cause of the 'mayonaisse' in the rocker cover.

Have a search through the projects section and the technical and problems section of the site and see what questions and answers there are on here, it's a subject that's been covered a few times on here with some good responses.

[Garagiste]

Well my knowledge only comes from that linked thread!
Assuming it's accurate it sounds like it though - assuming there's no emulsion / water on your dipstick? Do you have a non - vented cap?

[biggav]

Well my knowledge only comes from that linked thread!
Assuming it's accurate it sounds like it though - assuming there's no emulsion / water on your dipstick? Do you have a non - vented cap?

the sump is clean!!! i'm runn ing a 1380 stage 4

[mini93]

when the oil heats up and cools down ofetn and quickly like short journys not getting to the right temperature it throth's kinda(emulsifies) which is the "mayo" thing its realy not good for the engine to take short journys, and yet i still do it all the time and no doubt will always do so

[the beast]

i had a cap on my rocker without a hole and i had mayo on it most of the time .my car is leaking oil so i had 2 keep filling it up when i was on my way 2 camp the heater went off and the windscreen wiper water wasn't working so i thought one of the fuze's had gone but when i took the bonnet off there was oil all over the place.i could,nt get a cap straight away so i found a waterbootle cap witch fitted great but on the way home i pulled over and the cap had gone so i had 2 travel back 2 wales i just about got home 4 the last 25 miles i had 2 pull the choke out . anyway i got a new cap but this one has a little hole in it is that right.

[steveobennet]

i was always told there are a few reasons to fit rocker cover breathers. first is if you have a high reving engine, to help all the gases created escape faster. also if you fit a timing belt kit it removes the breather on the timing chain cover, so its good practice to put one on the rocker cover.

[Clubby1275GT]

thanks for the replies guys, but we kinda drifted off topis there, im not talking about rocker caps, im talking about the breather than usually goes (on the ones ive seen) at the back right of the rocker cover, its normally a small tube about 1 inch long that sticks out.

Just wondered about the pro's and con's of these and what engines they came standard on and does anyone have them on there car?

[fatmini]

ive only seen them on early 998cc engines

Edited by fatmini, 04 April 2007 - 09:05 AM.

[Jammy]

Basically, if you don't have a breather on your rocker cover you should have a breathable rocker cover cap. These are service parts and should be changed every 6 months.

You don't need a breather (or breather take off) on your rocker cover unless you have a highly modified engine. The standard breather points should be capable of removing the crankcase pressure, but you should ensure that they stay unblocked.

[Clubby1275GT]

thanks jammy, bang on just what i wanted to hear

thanks guys, im now much wiser in the ways of rocker breathers