if uve seen my other posts (and i appreciate all who have helped! tracyRR especially, why i come to this site for the actual reply and help) ive been fighting my rear mount turbo set up for almost the last 2 months with oil leaks from the turbo (2 diff turbos, im running out of time of having my car down and been broke lately tryin to get it going again, its a rear mount with MP T76, has a mocal high temp diff return oil pump, just recently put a check valve on my return line also RIGHT after the 90 degree on my turbo so it dosnt back feed oil anymore, my feed line is -4 AN and i put a restrictor in it that (if i was to guess) about a -2.5 maybe -2 AN hole size give or take, its flowing oil out of the pump and back into engine steady constant about 1/4inch thick stream, if i get in my car and drive it around it drives great, u can hear the turbo spool np, i can hit 4psi (what im set at atm) if i want with out a problem, havnt hit boost much cause its untuned atm (havnt been able to get tuned because of these problems) but blows oil out of the exhaust, no smoke or anything, it just oil soaks the bottom of my car if i was to guess with maybe a mile drive i might lose close to 1/4 quart of oil if i go out and drive (DP isnt hooked up atm). im at a loss and very close to sellin the whole kit just to get my car back on the road, i just hate to be this far and basically done minus this oil leak, the turbo is also brand new but i installed it before the restrictor and return check valve, saw i still had a leak after new turbo, parked car didnt drive looked around on here and such sounded like i should put a restrictor in so i did and for $12 through a one way check valve in the return right off the turbo so i could take the back flow problem out of the equation

now with all that being said, how long would a turbo take to clear oil out of the turbo if the restrictor is working and the turbo is oil soaked from before i would think it would burn it off with a few mins but, and if i leaked oil once through the turbo for any of the above reasons would this instantly kill my seals?

 

Is the T flange on the turbo level with the ground? Where is your drain going into the pan?

 

Im trying to figure out why checkvalve is after the turbo?

It should be right above the turbo on the supply line. Since its above the turbo.

Next, i couldnt follow your post very well, (please space it out some next time ) But are you able to see where the leak is coming from? Where is your feed line coming from? did you drill and tap the block off above the filter?

If so, have you made sure thats not leaking?

Im completley lost, i ran a -4an supply with no restictor and a -12 to the pump and a -10 from the pump to the motor, i NEVER dropped a drip of oil. Returned it to the valve cover back then.

 

A check valve on the return would only make things worse if the pump is running all the time. It's a restriction, even more so if it's behind the pump.

 

Exactly, if the checkvalve has a higher cracking pressure, then its feasible to think that oil could push past the turbo seals first during shutdown or sitting completely off.

OP, move the checkvalve above the turbo, as close as humanly possible to turbo inlet, and their is no need for a restrictor, -4 is about the standard, maybe a -3 the least.

 

I have to agree with both of them. The one-way checkvalve is designed to have a pressure push thru the springloaded valve, and gravity itself is not enough to push it, that's like pinching your return line.

 

ight was annoyed when i made the first post tbh so lol, sorry on the confusion

the feed line does have a one way check valve about 1 inch from the feed flange on the top of the turbo, it has a 1psi cracking pressure. it seems to be working fine, if i unbolt it nothing flows out but its obviously putting oil into the turbo

im not getting any leaks in lines or anything its all coming out of exhaust exit side of turbo, maybe compressor side too but hope not

the feed line is directly on top and is as straight up and down to the return being on the bottom as possible, i currently dont have a phone or camera or id take some pics : \

for the return line i originally didnt have a check valve in it thinking the pump would hold off the reverse flow after shutdown but i figured i could try since im still having problem with it,

as of today i narrowed it down a little more, started the car for the first time in a few weeks, finally got off and time, as soon as i fired it off it blew about 1/4 to a half of quart of cleanish oil out of the exhaust side onto the ground, after driving around and clearing up it hasn't dripped at all since then, i drove the car to work and have parked it and when i get off im see if it does the same thing on start up as it did at lunch

98Z28CobraKiller, when u say T flange u mean my T4 exhaust flange on my turbo bolts to the hot side of my exhaust flange or were the oil lines bolt too?

i did the oil restrictor and return line check valve at the same time would you guys recommend taking the return line check valve out and trying just the restrictor in the feed line if this problem persists then and see if that fixes it?

thanks all!

 

Yes, Get that check valve out of the return, the oil that comes out of their is not under pressure. It Drains out, thats why front mount guys and people with low turbos have to be careful to get angles right or use a pump.

That check valve on the return is more then likely your problem.

 

Yeah, I was refering to the T4 flange that the turbo bolts on to the hot/pressure side of the exhaust or more specifically, that the shaft in the turbo must be horizontal/level to the Earth just as the feed/drain axis should be perpendicular to the Earth.

Also, where does your drain enter your pan?

The check valve on the feed is fine. The one on the return, before the pump, is NFG. If you are going to have one, you want it right AFTER (outlet side of) the pump. Can you put the scavenge pump on a switch and run it for a sec after you shut the motor down? Basically suck the turbo dry before you walk away from it. Keep in mind that what comes out of the turbo is not as dense as smooth flowing oil. It is a frothy mess so you want free flowing, open volume of line between the turbo and the pump.

 

ive thought of this before, i wired it to my ignition so when key is on its on, thought about shutting it off then turning it back on with the engine off but pump on to do that for like 5 secs.

for the return i actually tapped the oil fill cap (yes not the cleanest way or best at all i know but did it so if i had to put engine back to N/A i can with out replacing a lot of stuff and i didnt have to go indepth in taking the pan off and all, kit started off as a cheap lets see if i can get the basics to work but) if yall feel this is the main reason i can get my pan tapped and fix this problem cause the return line does go along my subframe then up to the cap but

for the turbo angle the shaft is pretty horizontal and its all pretty well squared off for the feed/return being perpendicular and all.

if i had backed up oil in my turbo how long will it take to clear it all out if i fixed the problem? so i know how long to keep driving so if it is fixed i dont see left over and think its still doing it, my guess is a few mins of driving at operating temp but not sure

again this all helps so lol!

 

o and ill try removing the return line check valve when i get home but just specs on it its -10,1/2 one way valve with 0.1 cracking pressure, so i can see were this would be a restriction if ur just tryin to get the oil out of the turbo and away, i was just thinking more of it shutting off and the back flow but

 

IIRC, all the rear mount guys were putting check valves on both the feed and return lines, for the reason above (when you shut the car/pump off, you get drainback).

 

OP, have you verified if you are actually getting return back to the cap? Pull the cap while its running, and check to see if oil is flowing back.

And a return line checkvalve is not needed. Mine left the turbo and went almost straight up to the pump and i NEVER had drain back,

ALSO, we had a problem identical to a problem you are having on a friends GXP we rearmounted, turned out, the guy who wired the pump for power wired it backwards and it was pushing oil to the turbo.

Check both of these things then get back to us.

 

Pics of return as it leaves the turbo?

 

Have you checked our your pcv system? Too much Crankcase pressure can blow turbo seals. I wouldn't imagine that sort of pressure could outdo your pump pressure, but you never know. I replaced 2 turbos on the same truck last week for this issue. I'd put a new turbo on, fire it up and within the amount of time it took to build crankcase pressure, I'd start blowing oil out of the exhaust. this was with a -2 restrictor and completely unobstructed -10 return line. As far as knowing wheter it's fixed or not, can you easily remove your downpipe? just start it and let it idle with no downpipe, you should easily be able to tell if it's fixed or not.

 

https://ls1tech.com/forums/forced-in...turn-pump.html

this is when i FIRST finished it,dont have camera and phones down for a week or so so cant up load new pics but this is basically it, i have a diff turbo now diff hot side setup, same idea just a lot cleaner done and all but the oil lines are all the same basically, the return is a 90 degree though not a 45 and has the check valve installed right after the 90

and yeah i checked for the oil return back through cap, when i first did this i started it up and got a friend to watch the cap to make sure it came through, took a few secs but it comes out with out a problem

and new update as of this morn i drove it to work to see if it would act up etc, well it didnt leak any over night and on start up it didnt blow a ton out ether and didnt seem to leak any on the way up, when i take lunch im lookin over it all again, might be fixed for once

 

did you remove the checkvalve on the return?

 

no i havnt removed it yet as i would have to get more -10 line to fill in its space and was going to mess with it when i got off work today but i came out to my car to leave, rolled window down and regulator went out and broke it so wasnt in the mood after that, feels like im not made to drive this car anymore lol