sudden increase in oil pressure, then i brokeded teh turbo

**love ke70** · 12-07-2007, 08:10 PM

hey guys, havnt bothered posting this up until now as i have been avoiding the subject of blowing up the 1g ke70 again.
but i just thought i would throw this out there to see what people think, so here goes.

right, to start with, ever since ive had the car, theres been a slapping shim, i rebuilt the motor, reseated the valves etc and reset the valve clearances expecting it to go away.
nope, didnt fix it.
so one day i redid the shims, nothing out more than a thou or so, but anyway, it was still like it. and it sounded like one of them was REALLY slapping, even though they were all in spec.
so a few months later i sent it into the mechanics (reputable) and they pulled it apart, and measured up, decided, yes, the clearances are right but the lobes on the cams are worn, so thats causing the slap.
made sense, so i swapped to a good set of second hand cams, nope same noise, emanating from the same place, i reckon its always been to the back of inlet side, but no professional was willing to comment on that matter.

so anyway, with these new cams fitted, i noticed when cold the oil pressure would get up around 70 or 80 psi by 3000, most ill rev it too cold. and when hot, and cruising highway it would have oil pressure around 55psi.
before i swapped cams it would sit dead still on 60 when cold after about 2000rpm, and would sit between 40 and 45 when hot on highway cruise.

now all that i changed was the cams.
can anyone think of a reason for this? seemed strange to me, and made the car leak even more oil than normal. YES, i was going to get around to fixing the leaks!

so i drove it anyway, coz i cbf pulling it apart to fix something i didnt know the cause of, so anyway, drove down the coast, went out for dinner, drove back to missus place, left there when i woke up

and about 2km from home, coming round a corner, feeding in the throttle and its coming onto boost i here this tink tink and the boost is gooonneee.
i thought i had blown a intercooler hose off, ive done it enough times before, and it felt and sounded just like that.
so i babied it home, and realised it was idling fine, which it never does when i drop a hose, so i had a look, all pipes in tact.
went to bed to look at it in the morning.

in the morning, i had a look, yep, all connected, and definately no boost, so off with the dump pipe, and as i had predicted, the rear wheel in the turbo was...ahem....kinda....not there

yup, another shitty rb20 turbo bites the dust

so, the turbo i just put down as component failure, and the car is going to get de-registed and a new head built and a new chassis and everything fixed all over again, hopefully ill get it right this time round.

just wondering if anyone had any thoughts on the oil pressure, turbo, or head/shim slapping noises. or anything else they wanted to talk about in relation to my shit box it would be appreciated.

cheers, andrew

**oldcorollas** · 12-07-2007, 08:43 PM

slapping noises, blocked oil supply to that lifter

change in oil pressure with cams, the cam journals may hav ebeen slightly bigger, decreasing the clearance and the rate the oil leaks out.. ie, increasing the restriction.

basically, if you are going to use the engine again.. get the oil passages in the head and block completely cleaned out as good as you possibly can and set up clearances correctly..

as for turbo, it probably just broke

unless it got starved of oil because of the blockages?

**jeffro ra28** · 12-07-2007, 09:16 PM

pretty sure stu has hit the nail on the head. What else can happen is the relief valve in the oil pump sticking, causing your high pressure. I have had a slapping sound occur in the oil pump relieif valve on a turbo diesel td42 engine aswell. Not sure if this would be relavant to a 1g oil pump tho.

**thechuckster** · 13-07-2007, 12:13 PM

andrew: the oil feed line to the RB20 turbo should have a restrictor. Check the inside of the banjo fitting. If that's blocked then the turbine bearing will rapidly die. If you didn't have a restrictor then you should have had oil leaking past both zorst and intake-side seals (with lots of accompanying white smoke)

Does the compressor wheel rotate easily (if so then i'ts not oil feed that's the problem)?

These things only push about 7-8 psi on the original motors, so (like me) we're both runnning these cheap, disposable turbos up at the top of their efficiency range - end result is the wheel/shaft on the hot side failing and the turbine wheel being collected in the CAT/zorst.

**love ke70** · 13-07-2007, 03:39 PM

oldcorollas: that may be a possibility. i dont particularly like this head so i may get it inspected or i may piss it off and start a fresh. this head is gonna have the works, so im sure it will all get checked out properly. just a thought, if the oil supply was blocked, would after 5000km there be a pretty obvious indication. because its done over that post rebuild and nothing was excessivle worn...

jeffro : i wondered if it was the relief valve, but its a pretty weird time to do it. oil pump isnt even a thousand k's old and the car was only off the road for 3 days...

chuckster: bearings are still good. the rear wheel just disappeared, pretty sure ill find little peices of it in my muffler, or just before the hump for the diff

i was only running 9 pound, stock gate and everything i think the gas may have made it run a bit more boost due to the higher egt's...maybe
i think they are pretty unrelated problems. for what its worth, where the ceramic wheel joins into the steel shaft, its virtually clean in there, so its almost as if whatever holds the two together stopped holding

which of the two oil pressure ranges i had would be the more normal/desirable pressure?

and just another question, when i pull the head off, i was thinking about measuring piston-bore clearance. how is this done, ill check it against stock figures and make sure it wasnt piston slap, im pretty sure it wasnt though...

cheers

**thechuckster** · 13-07-2007, 03:51 PM

i think they join them with a weird friction weld or some wacko adhesive -

your cold oil pressure on revs is a bit high - otherwise they're healthy numbers. Did they shim up the oil pump relief valve? Might explain the high cold reading?

Do you still have the donut cooler/heater where the oil-filter attaches to the car?

re: piston/bore clearance - measure piston size and bore size at 2 points (at skirt/pin and 90 degrees around from there) and subtrack difference?

**love ke70** · 13-07-2007, 04:08 PM

nope, i didnt shim the oil pressure relief valve. im wondering if it has stuck, seeings as it used to peg its self at 60psi and not move pre cam change.
all will come out in the wash when i pull it down.

i was hoping to measure the bore clearance without taking the pistons out, coz im lazy.
was wondering if measuring the ring gap may work, just didnt know how to measure the ring gap, cant get feeler gauges in there

**jeffro ra28** · 13-07-2007, 05:27 PM

Andrew, there is no proper way to measure piston-bore without re moving pistons and measuring them also.
However, you can get a rough idea if you measure the bores with a bore gauge, and compare that against the specs for the pistons used in th engine. eg. .010", .020" oversize etc.
There should be some specs available for the stock pistons size. Even if they are oversize they should have specs listed for them somwhere.