Thread: TD5 blow-by remains

Originally Posted by spudboy

Phil - can you tell me a bit about how this works? Can you use it for testing for leaks as well?

Thanks
David

no probs, drain the system at the lowest possible point, to get as much coolant out as possible. then re connect system. in a clean bucket have on hand the ready mixed up coolant and make sure its a liter more than you require. connect an air line to the filler, the filler is then pushed into the expansion tank opening and a button on the filler is pressed allowing the compressed air to creat a venturi in the filler that vac's out the system, it will flatten your radiator hoses if you have got it right. also on the filler there is a vac gauge, when the system is completly sucked it will show on the gauge, at this stage you stop pressing the air supply button and watch the vac gauge, if it starts creaping back or it wont get to the green zone then you have a leak...somewhere....
once all the leaks are sealed and the vacuming is complete put the hose on the filler into your coolant and turn the tap in the unit. in about 20 sec your system will be filled to perfection...

its a bit to explain but after the first couppla tries you will wonder why you ever did it any other way.

cheers phil

Hi,

Quoting thorby: 'all engines creat blowbye as there is a certian amount of compression created by the pistions going down. if you completly sealed a motor so as no gasses could escape except through the exaust it would stall'

Wouldn't the crankcase compression caused by a couple of pistons moving downwards be counteracted by a couple moving up at the same time creating a vacuum? The displaced volume is the same.

DL

DL - I was wondering about the same thing ?

Phil - you don't have to try the vacuum filler a couple of times, just once and your hooked.

I left mine on vacuum for nearly 60 seconds in awe and absolutely no leaks on the cooling system. When the gauge reached zero I had to give it a bit more vacuum to get the system full.

The combustion tester also gave negative results on the water system, and I filled both chambers with indicator. Then, as it was a new toy, I decided to plug it into the oil filler cap and left it for 2 minutes. Zero discolouring. Then just to test I walked to the exhaust and in seconds the indicator turned green.

So my "blow by" is not combustion gasses ? AND if it is things moving up and down in there, where does it get the air from. The video wasn't intended to show sucking and blowing, but trust me it is only blowing. Mind you I've noticed almost no blow-by when the engine is really cold and lots at running temp.

they will make some pressure but thats what breathers and PCV valves are for. its different in the sump because its not a sealed area, well not like a head anyway....
i dont think 350rrc's quote is quite correct because if it were completely sealed it would be neutral?? i think, as it would need air intake to continue to pressurize.

to me your statement that theres minimal blowby when cold to alot more at temp still points me to piston/ring/bore clearance being to big..
the hotter things get the greater the clearence.

to get closer to an answer you need to do a cylinder leak down test and a compression test. these 2 will point you to a deffinate answer.
another thing, were the taper face rings installed the right way up??

looking at the manual there is a fair amount of differance between the EU2 and EU3 engine assembly ie pistons, rockers.

cheers phil

Disco white,

(reminds me of the Bee Gees) I wuz just asking a question really.

cheers, DL

Originally Posted by discowhite

they will make some pressure but thats what breathers and PCV valves are for. its different in the sump because its not a sealed area, well not like a head anyway....

Not sure what you mean here. The rocker cover / valve gear area of the head IS common to the crankcase thru things like oil returns. Unless you mean the combustion chamber/valve face area???

i dont think 350rrc's quote is quite correct because if it were completely sealed it would be neutral?? i think, as it would need air intake to continue to pressurize.

The "air intake" would be the blowby gas. If you sealed it, pressure would eventually blow a rocker gasket or similar if it didnt stall first.

Even with new rings and a hone, nothing has bedded in and there will be some initial breathing.
With regards to the honing, you need to measure first for size, cylinder out of round and piston to bore clearance. If any of these are at the limit or close to then even a hone can take this over the maximum tolerance which in turn will make things worse than they already are.
Not sure if these are liner or parent bore, but in reality you dont hone liners.
Plus, when honing you need to ensure you have a cross hatch of about 60 degrees.
Once honed, ring end gaps need to be checked at two positions in the bore, this also shows any out of round in the bore.

When you consider that diesels have a CR anywhere between 18-22:1, you will get blowby, how bad depends on your tolerances. Its not as simple as a petrol engine unfortunately and room for error is much tighter.

Cheers
Andrew.

it was in referance to the pressure generated by the underside of the piston. hence the bit about PCV. positive crankcase ventilation.

cheers phil

OK - I'm going to live with the blow-by... for now. Look common sense aside, after 2 tries at honing, measuring and new rings nothing has changed. It's not more or less.

This is caused by something else. What, I don't have the foggiest idea. I also replaced the injector seals last night with no difference. Conclusion - I'll wait to see what brakes.

Oh and with regard to my strange temp readings - the coolant sensor was a 120'C VDO and both ones I have seem to go weird at around 100'C. I purchased a 50-150'C VDO and problem solved.

I'm about to do an oil change. Can I move up to 20W60 Helix high milage or stick to my Rimula X at 15W40. I've done 615km's now, the cheap oil seems fine and new still, but I'm now pedantic about cleanliness and contamination. Summer over here so no cold mornings for a while.

Thanks