RB25DET high oil psi causing much white smoke?

[DigitalBHP]

The background for this question is a long sad story from which we will emerge victorious. The shortish version is last summer we purchased a 1989 240SX with lots of goodies installed the highlight being the RB25DET with Precision Turbo SC60 engine swap plus appropriate driveline and suspension upgrades. The day we bought the car we drove it home 750 miles and it ran great and continued to run fine around its new hometown. Actually better than fine as it tossed off a 300 rwhp chassis dyno run on low boost. After only 5 days with the car our happiness was dashed when a drunk driver blew thru a stop sign and T-boned our driver's door. Thank God my son and his friends were not hurt but the 240SX saved them by taking the energy into her chassis leaving it well and truly bent. Less than a week of proud ownership and our new toy was totaled. Not willing to let the damn drunks/druggies win another round a clean 1990 240SX was located, the auction won and another 1500 mile round trip brought it home. Lacking the heavy lift equipment for engine, driveline, and suspension swaps a local shop was hired to pull the four banger out of the 1990 and swap the parts from the totaled 1989 into the 1990. My son and I took on the task of swapping and debugging the modified wiring harness + Apexi FC ECU along with all the miscellaneous bits. The engine and electronics are accomplished which brings us to first startups and today’s question.

With the last wiring harness issue sorted (you really do need 12vdc on that 7th contact of the injector harness) the RB25DET started for the first time in the 1990 chassis. Noted a little white smoke out the exhaust but dismissed this as the engine had been sitting for a few weeks. Oil pressure was as high as 100 psi which I judged to be another wiring glitch so the engine was shut down and connections to oil pressure sender reworked. With the sender's ground and signal wires sporting new crimped and soldered lugs another test run showed the oil pressure still high. My son recalled seeing temporary periods of high oil pressure before the wreck and my 911 has always had high oil pressure until it warms up so I decided we would do a tentative once around the block test drive. However while warming up the engine for the test drive and checking for leaks we noted the engine was still smoking, this turned into a LOT of white smoke out the exhaust pipe. Abort the test drive before it begins and shut off the engine immediately.

So the BIG concern is that high oil pressure is driving oil past the hot side turbo shaft seal into the exhaust. Obviously we hope the seal has survived its ordeal. The dilemma is how to determine if this theory is correct and the smoke is in fact a result of high oil pressure overcoming the turbo's shaft seal or if our smoke screen as some completely different source?

What is the expected nominal oil pressure range for a RB25DET? What are the possible sources for high oil pressure? In hindsight it occurs to me when checking the oil before our initial start ups the oil level was a bit high, about 1/16” above to top mark on the dipstick. Could too high an oil level be the culprit, perhaps blocking the oil return drain from the turbo?

Thanks for sharing your expertise and helping us get our RB25DET S13 back on the road.

[Darius]

Glad to hear your son and his friends are okay. 100 psi with cold oil is normal. It usually takes some time to warm the oil up even after the coolant reaches operating temp. It should drop as the oil warms because it becomes less viscous. 20 psi is normal at idle on warm oil.

I'm not sure about the white smoke. If it hasn't been run for a while, there can be condensation in the exhaust pipe. Let it idle for 10 minutes, then take it out for a 10 minute drive while watching the water temp.

[gmac708]

Usually, white smoke is water, blue smoke is oil, black is raw fuel.

If it is water system, It would be easy to pressure test your coolant system to see if you have head gasket leaking. Could also be a cracked head Also white exhaust will have a "sweet smell". Kind of acrid if that makes sense. This would be the anti-freeze mix burning.

A good question to start with about the high oil pressure would be where is the pressure transmitter tapped into the system? Stock or remote adapter? What filter? What viscosity/type oil?
My RB26 is about 70 PSI start when cold and about 15-20 hot at idle. Pressure at remote filter return location. Royal purple 5W-30 synthetic. Oil filter is K&N.

It might just need to get a few miles on it to clean up any sticky rings or something like that. It did sit around for a little bit. Maybe a good road trip would clear any problems or indicate water or oil consumption. Just keep an eye on those service levels.

Gord

[Darius]

Like I said, your oil pressure is fine.

Use this and get back to us:

http://www.blockchek.com/

[boostedh23a1]

Is the pcv hooked up? Oil catch can? Vented to atmosphere?

As for the oil, i had a N1 oil pump on my rb26 and it saw about 90 at idle and 105 over 3k... The N1 shattered so i got a tomei one and it sees 100 at idle cold, then down to 50ish idle warm and 115 over 3k.

[supermario680]

I would look at the PCV set up, mine was smoking white significantly until i fixed the PCV system.

[Darius]

+1 I had an oily breather filter that prevented the crank case from venting and it smoked white smoke like crazy.

[DigitalBHP]

Time for an update. First off thanks to everyone for the advice, without your inputs we would truly be RB25DET noobs lost in the woods.

We tried another test start to narrow down the oil or coolant question and hoping “might just need to get a few miles on it to clean up any sticky rings or something like that”. Yeah, no such luck. Again lots more smoke increasing in volume as the engine heats. Made enough smoke this time to be certain its oil. Smells just like my 1974 911 after it’s been run and the oil leaks from that bolted together decades old air cooled engine have weeped out on the hot parts. Speaking of weeping my son and I were almost to that stage thinking it has to be a blown turbo. But men don’t cry (at least over broken cars) so instead just depression and racking the brain over how does a turbo get blown in an inactive car. Did the mechanics who swapped the motor for us drop a bolt in it!?!!! A possibility but then you guys come to the rescue with the suggestions to check the PCV system. With comments like “mine was smoking white significantly until i fixed the PCV system” and “I had an oily breather filter that prevented the crank case from venting and it smoked white smoke like crazy” this is a lead I have to chase to the ground.

Education begins with Factory Service Manual. Turns out you guys are clueless the RB25 has no PCV system. Oh, wait. What’s this “Blowby hose” and “Blowby control valve”. Cool, “Blowby control valve” is WAY more macho than Positive Crankcase Ventilation valve! Given the aftermarket bits on our car including GReddy intake manifold it is no surprise what I find under the hood does not look like the diagrams in the FSM. Humor me while I describe our setup and my plans and speak up if anything sounds obviously wrong. The Blowby hose connecting the two cam covers is in place. On the exhaust side cover Blowby hose fitting there is also a small filter not seen in the FSM but often seen in built engines here on NicoClub and elsewhere. It looks like a tiny paper air filter like one would see on a weed eater engine. Thanks to a T-fitting it shares the port on the exhaust side cam cover with the Blowby hose. On the intake side cam cover the Blowby hose is the only connection to that port. A different port on the intake cam cover has what the FSM identifies as the “Blowby control valve” stuck in it from which a hose loops down thru the intake manifold runners and back up to the side of the GReddy intake manifold. Looks like a PCV system to me. My plan is all this comes apart looking for blockages. I also want to check if routing the PCV valve to intake hose down thru the intake runner looks better but left a low spot where a gunk plug has developed. I am also considering if we can clean the PCV and breather filter or need new parts. Obviously new is preferred but I am guessing we will need to order these from a RB specialist and that precludes trying it this weekend.

Any and all suggestions on how you cleaned and debugged your PCV systems are welcomed.

[ItzGenX]

PCV valve can be checked by taking off the hose and sticking a paper clip in to see if the check ball and spring still work. If removed, you should be able to blow air through it going towards the intake but not the other way. The little 'filter' looking thing is usually a line hooked up on the stock intake piping just in front of the turbo (to help pull vacuum on the crankcase during times when the engine isn't pulling vacuum in the intake manifold using Bernoulli's principle). If that's not it, pull the charge pipe before the intercooler for an oil pool check. No go?; check the plugs for burned oil film, if none, check the turbine wheel. The key here is to check if there is just 1-2 plugs that are oily versus all 6. All 6 would indicate oil seepage from somewhere upstream, and no oil film would indicate the problem lies downstream. If it is just 1 or 2 plugs filmed with oil, then you can conclude it is either sometimes valve seals, cracked head, or blown head gasket. If it is the turbine of the turbo, simply pulling off the downpipe and looking in at the wheel should be able tell you if that's the culprit in extreme cases. Usually you'll see a 'wet' looking carbon film on the wheel if it has been puking oil out the back side. This is just off the top of my head right now, and I may be missing something. At the moment, it is the order of how I would approach it.

[Darius]

Here is a thread describing the dozens of ways the PCV system can be set up on the RB engines. I realize you don't have a catch can, but you'll get the picture after looking at the diagrams in this thread:

how-to-set-up-your-pcv-catch-can-breath ... atch%20can

[jetdriver]

Although you may see the filter on some "built" rb motors, that does not make it right in every application. If you are using a MAF and the pcv line to the intake manifold, then you need to replace the small filter with a hose Teed into the turbo inlet plumbing downstream from the MAF. This will match with what you are seeing in the FSM. The filter will be a source of non metered air through the crankcase to the intake manifold, leaning your tune anytime you are not in boost.

[DigitalBHP]

Another weekend in the books so here is the update on what was learned. Weather cooperated which is important because until the pulled 4-banger moves onto a new home the SX won't fit in the garage. We have been blessed with a mild Fall and early Winter so with a couple of layers of clothes we keep at it. Thanks again to all who have brought forward the ideas to check.

Lots of reading and thinking about PCV systems. Looking at the “blowby system” with the new knowledge Jetdriver is right about the weed eater filter being a source of bypass air downstream of the MAF sensor. When we bought this project I recognized we had cleanup work (before the wreck) so add that to the list. How happy we will be to get back to the state of just some cleanup chores! Presumably the Apexi FC tune somewhat accounts for the leak but that is not the way you want to do things so add that to the To-Do list.

Inspired by ItzGenX to be a bit more methodical I set aside the incessant look for “the culprit” wrote up a checklist and set about it. All PCV hoses and that pesky weed eater filter were clear and free flowing. A possible vacuum leak where the hose connects to the intake manifold was corrected with some RTV and a tighter hose clamp. The PCV valve seemed like it was stuck closed when I first blew on it. After cleaning the diaphragm and spring moved freely. We also got a replacement PCV valve.

As an aside when blowing on both the cleaned and new PCVs in the manifold to engine direction closing the check valve the sealing did not seem all that great. If they leak from my half century old lung power how do they hold back a turbo's spun up boost at full chat? Do later generation RB motors and high boost hot rodded builds use something more substantial? Not an issue for the present on our engine with our problem manifesting at idle and that weed eater filter absolutely preventing pressurization of the crankcase.

Back to Saturday's checklist debugging. Pulled all six plugs. No wet singles or pairs signaling head problems. All six looked identical with flat black burned carbon deposits. Not wet or burned tar like deposits but soot as if painted with flat black paint.

Still hoping for the best (call it denial if you will) I took the possible stuck PCV valve and evidence of soot black plugs that we did have a PCV problem so with everything cleaned and reassembled did another test run. Still much-o white oil smoke. Ran a few minutes to see if oil left in the exhaust system needed to burn off. No such luck.

Of course now its too hot to check the hot side of the turbo. With gloves on I removed the intake tube off the turbo inlet. About a pint of nice clean engine oil started draining out on the driveway. My first two thoughts were “get the kitty litter, we got oil to cleanup” and “now we know where the soot on the plugs is coming from”. Hope for a quick inexpensive fix drained away with the oil on the driveway.

So thus concluded Saturday, time to go to my great friend Leo's 80th birthday party. Of course as a fellow car enthusiast he asked “how's the car” and upon hearing the news had to repeat his story of the old mechanic who told him “turbochargers are like oil filters, every so ofter you have to change them”. Thanks buddy, salt in a fresh wound hurts but I hear it helps prevent infection.

So now the question is what killed the seals on this Precision Turbo SC60? It did 800 miles and a dyno pull and trips to school in the week we owned it before that drunk had to take out another 240SX. After the wreck it ran ok when we started it up in the disabled car #1. In those post wreck runs there was a little smoke attributed to infrequent running. A little smoke, nothing like the air show amounts we are producing after the engine swap into car #2. The shop I paid to do the engine, drivetrain, and suspension swap from cars #1 to #2 did disassemble the exhaust manifold and turbo assembly so they could lower the engine out the bottom using their lifts. We have noticed they managed to break off 2 of the 12 exhaust manifold studs (another addition to the To-Do list) so I am questioning if they botched something in the oiling system? Reading Gord's '2009 240Z' build thread he mentions oil restriction orifices so on Sunday I removed the turbo oil line and found no sign of any. The SC60's oil feeds from the block via Earl's aluminum fittings first thru a T-fitting for a oil temperature gauge sender then via stainless steel hose to a 90 degree elbow on top of the turbocharger. With no sign of a flow control orifice is it possible we had one that was misplaced and not reinstalled during the swap allowing too much volume of oil to overwhelm the seals?

Obviously the next step is getting the turbocharger out of there for a full evaluation. Advice welcomed as always. Our goal is a strong daily driver, NOT a 600 rwhp monster.

[ItzGenX]

Sometimes (not all the time), turbo manufacturers place a small conservative orifice in the CHRA feed hole where the threads are. It is more common on later ball bearing variants and usually a hair on the large side if present. I usually install inline screen filters with built in orifice restrictor (FP) for ball bearing turbos. For journal bearing or oil cooled units, I usually do not bother too much with the restrictor and use a AN -3 line to naturally control oil flow rates. If an aftermarket high flow oil pump is used, I always rock a restrictor regardless of turbo type, 2.5-3mm journal or 0.8-1.2mm ball bearing.

[DigitalBHP]

Time for an update, with the puzzle revealed.

In the two weeks since my last post we were slowed down by my catching cold and son’s senior formal on the first weekend but on the second we made good progress and the turbo and exhaust manifold are off the car. To get the turbo out we had to disconnect the downpipe junction about halfway back under the car. More oil on the exhaust side, enough to get the oil change catch pan out to catch it as it drained out of the pipe. With the exhaust side disassembled time for further diagnoses.

Note above I wrote: “The shop I paid to do the engine, drivetrain, and suspension swap from cars #1 to #2 did disassemble the exhaust manifold and turbo assembly so they could lower the engine out the bottom using their lifts. We have noticed they managed to break off 2 of the 12 exhaust manifold studs (another addition to the To-Do list) so I am questioning if they botched something in the oiling system?”

So, with the turbo and exhaust manifold out of the way I can see the turbo’s oil drain pipe is full and not draining into the oil pan. On this Precision Turbo model the drain pipe connects using a two bolt flange, I can see the mechanics used a little red high temp RTV to get a good seal, wonder if they let it clog the drain? With oil catch pan ready for the tube full of oil I loosened the hose clamp and pulled off the ~4” long section of drain piping rushing to plug the end with my finger. Funny, only a couple of drops of oil came out when I turned it upside down over the catch pan. With that thimble of oil out of the way I can now see the red material around the flange is not RTV but the top of the service plug left in the drain! How’s that for a box full of Murphy’s Law wrapped up in irony?!?!! Being good professional mechanics the guys at the shop plug the open oil drain to keep our oil pan clean, then get in a hurry during reassembly and miss pulling the service plug leaving the oil line blocked. The plastic lip of the service plug made a good gasket so when we test fired the engine and oil at up to 100 psi was pumped into the turbo there was nowhere for it to get out of the turbo except past the turbo shaft seals into both the hot exhaust and cool intake sides.

Sunday ended with mixed feelings, pleased to have finally located the problem. Pained (in the wallet!) as I could not imagine the oil seals in the turbo had survived and expected to be sending the unit off for a rebuild.

On Monday I called Precision Turbo and explained the torture the turbo had been subjected to. I was thrilled when they said it should be ok and there is no need to assume the seals need to be replaced. Note that this no rebuild needed opinion came after I reported the impeller turns freely with no sign of crunchy bearings or contact between blades and housing. They explained the seals in a turbo are not rubber or O-rings but rather metal like piston rings. Given the temperatures and RPMs in a turbo supercharger that makes sense.

So with the mystery apparently solved we are collecting parts for the reassembly and the next big test. The exhaust manifold stud kit is here and gaskets on the way so it shouldn’t be too long before I can report a final result. Thanks again to the RB owners and wrenchers who have helped us track this down.

[Darius]

Good news!

If the turbo is damaged from not having any oil flow through it, I'd make the shop pay for the replacement parts/repairs.

[ItzGenX]

Wow what a bunch of blind folded shop monkeys! It's good to hear you found the problem though. I can vouch for the turbo 'seals' though. I have rebuilt so many journal bearing turbos, and I never understood why people call them seals when they seem more like rings. They remind me of miniature piston rings. Some even look like those Total Seal piston rings. Oil weeping through them when the oil has nowhere to go is fine. As long as the oil didn't cake up in there and fry a bearing, things should all be fine. It's things like this that make me rather learn how to build and do things myself instead of letting someone I don't even know touch it.

[Darius]

It's things like this that make me rather learn how to build and do things myself instead of letting someone I don't even know touch it.

This is exactly the way I feel about all mechanics. I don't let them touch my cars, not even for oil changes. When I was 16, I had my oil changed twice where they didn't refill it with oil. I drove home 2 miles and wondered why the engine overheated. Saw the oil cap laying upside down on the valve cover each time.

However, the exhaust studs breaking off is not the mechanic's fault. That is a known fault on RB motors. They are always broken or break when you try to take the manifold off. I lucked out and was able to use a vice-grip to twist mine out. Other had to resort to more drastic measures.

Keep us posted on the rest of your build.