Breather blowing - blowby or something else?

A

ajstok

New Member
Joined
15 Apr 2006
Messages
4
Visit site
Hi folks, we were out this week. Both AD41As (which have been started over the winter with no problems) were OK then noticed a loss of power in the starboard engine. 'Found that the breather was blowing quite a lot of black smoke...Next day thought we would see what was going on having considered overnight the probability that this was a cracked ring / blowby etc.
Started her up, no significant noise from any of the cylinders even listening through screwdriver etc on block. A reasonable amount of black smoke evident from breather at start up i.e. not even warm. Cracked off each injector - only one made a significant dfference to revs. Did some compression tests (tester not brilliant) but got readings of 300/200/300/250/300/300. No water in oil. Questions. 1) If No2 is down, is it down enough to produce such a lot of smoke / blowby / is this likely to be a ring gone? 2) Black smoke from breather at start up - could this be exhaust and therefore a head gasket issue?
As we are reluctant to take the engine out just yet any ideas on other causes / things to check would be much appreciated. Cheers.
 
ajstok said:
Hi folks, we were out this week. Both AD41As (which have been started over the winter with no problems) were OK then noticed a loss of power in the starboard engine. 'Found that the breather was blowing quite a lot of black smoke...Next day thought we would see what was going on having considered overnight the probability that this was a cracked ring / blowby etc.
Started her up, no significant noise from any of the cylinders even listening through screwdriver etc on block. A reasonable amount of black smoke evident from breather at start up i.e. not even warm. Cracked off each injector - only one made a significant dfference to revs. Did some compression tests (tester not brilliant) but got readings of 300/200/300/250/300/300. No water in oil. Questions. 1) If No2 is down, is it down enough to produce such a lot of smoke / blowby / is this likely to be a ring gone? 2) Black smoke from breather at start up - could this be exhaust and therefore a head gasket issue?
As we are reluctant to take the engine out just yet any ideas on other causes / things to check would be much appreciated. Cheers.
Click to expand...

Black smoke is an indication of un burnt atomized fuel, so doubtful it's exhaust related.
The fact that the breather is blowing might be the intake for the crank case is blocked or its blow by in a cylinder, The one cylinder that did change the engine sound is the only good one, unless you did not fully crack the others.

I would re start and warm the engine then replete the injector crack test to locate the bad cylinder/s make sure the breather is not feeding into the intake when crack testing, or the unburnt fuel may compromise the results. If nothing shows further the crank case plumbing.

.
 
Last edited:
Sorry but a 30% variance in cylinder pressures is not a good omen, nor is excessive crankcase pressure and smoke from the breather.
Maybe something like stuck rings. Try pouring some redex into the cylinders, leave for 48 hours, spin the motor before reinstalling the injectors, you don't need an hydraulic lock and try starting her again.

Same result on running and on the post run compression test and I'm afraid its strip time.

Edit

Did the engine falter under load or fail to respond fully after a reduction of power?
 
Last edited:
ajstok said:
Hi folks, we were out this week. Both AD41As (which have been started over the winter with no problems) were OK then noticed a loss of power in the starboard engine. 'Found that the breather was blowing quite a lot of black smoke...Next day thought we would see what was going on having considered overnight the probability that this was a cracked ring / blowby etc.
Started her up, no significant noise from any of the cylinders even listening through screwdriver etc on block. A reasonable amount of black smoke evident from breather at start up i.e. not even warm. Cracked off each injector - only one made a significant dfference to revs. Did some compression tests (tester not brilliant) but got readings of 300/200/300/250/300/300. No water in oil. Questions. 1) If No2 is down, is it down enough to produce such a lot of smoke / blowby / is this likely to be a ring gone? 2) Black smoke from breather at start up - could this be exhaust and therefore a head gasket issue?
As we are reluctant to take the engine out just yet any ideas on other causes / things to check would be much appreciated. Cheers.
Click to expand...


The only good cylinder is the one where the revs drop....The others are all on holiday and this is probably due to poor injectors which may have done all sorts of other damage.

I would suggest first take all injectors to a workshop if the retest still shows only a rev drop on one cylinder and then see how she performs with good injectors before following the doom and gloom advice. One you start re lubricating the liners instead of washing them with diesel things might improve.

Could be worth checking the sump oil level to see if it has come up a bit and also take a sample and see if it smells of diesel. I d change the oil anyway if the injectors were all hosing as there could be a high percentage of diesel in the oil.

This is the recommended way of burning holes in Volvo pistons so lets hope you were not successful here.
 
If there is excess smoke from the breather after a run out and power loss then its a piston problem, though your figures are not that bad.

Just on with a tamd 41 a at the moment, the comp figures were a lot less than those of yours.

The piston ring wear figures were way in excess of the safe permitted figures in the manual, and im afraid if the ats the case its new pistons and liners.

I have in thepast just supplied liners and ring kits using the old pistons, but ther is so much blow by in these pistons, its blown by the second ring.

Try changing the breather filter and stip down the little valve and clean it, have another run to confirm its condition then pray as its a few k to put right!
 
You must log in or register to reply here.

Share this page

Top