DETurbine Posted January 24, 2005 Share Posted January 24, 2005 Well it is finally time to see what is wrong with my motor (RB25DET). Ending of last summer I was tunning my car with my new Nismo FPR and while in the process of doing some test pulls blew my motor. I gave it a pull and noticed an dramatic power loss followed by smoke pouring out my exhaust. I then took it back to my friends house (a few blocks away) and opened the hook to see oil sprayed on the side of my strut tower (shot out from my HKS BOV). We then did a compression check on it and it was as followed....first 5 were about 110psi and cylinder #6 was only 25psi. We looked into the cylinders through the spark plug wholes and noticed quite a bit of oil in the cylinders, especially #6. I took the intake piping and intercooler off and it was drenched in oil. A few days later we start it again and start to notice that it is making a sputtering/ knocking kind of noise (not sure if it was really knocking, to me it sounded like more of a compression sputtering noise). I am not sure what the problem is and wanted your guys opinion on what it could be. I am going to do a leak-down on it at the end of this week to narrow it down and hopefully find out what the problem is for sure. Just wanted to see what you guys thought before I did that. When it blew I noticed a dramatic power loss and it seemed like blueish/white smoke. I did not notice if the water temp was climbing or not, since his place was only two blocks away. Before this had happened I have always noticed oil coming out of the turbo, so I am sure that is where the oil came from and probably totally gave out when I turned up the boost to 14psi on that test run. I took my top section of the intake manifold off a few months back and noticed that there were puddles of oil down the gallies. I am really hoping that it could be the head gasket, but something is telling me since the compression test was an even 110 (almost all the way through) except #6 (25psi) that it is probably the rings or ring lands...or can a head gasket have that same compression test result?. Let me know what you guys are thinking if you could. Thanks, Zach Quote Link to comment Share on other sites More sharing options...
savageskaterkid Posted January 24, 2005 Share Posted January 24, 2005 Im pretty sure that u can blow a headgasket, and possibly only have it blown next to one cylinder, i think its happened quite a few times to ppl on this site b4. Whitish-colored smoke comming from your exaust usually means burning coolant, doenst it? meaning ur HG probly blew up. tell us how it ends up. Quote Link to comment Share on other sites More sharing options...
dmyntti Posted January 24, 2005 Share Posted January 24, 2005 White smoke would be coolant but the bluish smoke indicates oil. I sounds to me like you have a bad piston either blown through or broken ring lands. You need to pull the head to determine this for sure but it sounds like a rebuild is in order. Don't run it until you know for sure because a broken piston can scrape a cylinder and destroy the motor. Quote Link to comment Share on other sites More sharing options...
DETurbine Posted January 24, 2005 Author Share Posted January 24, 2005 The turbo went out for sure, so there was oil getting burned up, but not sure if it was all oil or coolant and oil as well. I know compresion can be lost on just one cylinder from a head gasket, but the compression was low on all of them. Average compression for the RB25DET should be 174psi, but the first five cylinders were at 110 and cylinder number 6 was at 25psi, I just didn't know if it was likely to loose an equal amount of compression on all the rest of the five cylinders if a head gasket were to go out. I am also thinking it is the ring or ring lands, just thought maybe it could possibly be a head gasket instead. Thanks for your guys input. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted January 24, 2005 Share Posted January 24, 2005 how did you do the compression test? pull all of the plugs and keep the throttle wide open while cranking? Quote Link to comment Share on other sites More sharing options...
cheftrd Posted January 25, 2005 Share Posted January 25, 2005 You have broken or burned pistons. 25's are fragile and won't tolerate much detonation. 90% of the time with RB's, #6 is the first to go. Are you still running the stock turbo and piping? If so, the oil coming out of the BOV could be from the crankcase vent into the turbo inlet. If it's on the right side of the engine compartment, it could also be from the dip-stick being blown out. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted January 25, 2005 Share Posted January 25, 2005 Chef - Did not realize 25s were that fragile...I always thought they were very stout and could take the lashings.... Yasin Quote Link to comment Share on other sites More sharing options...
DETurbine Posted January 25, 2005 Author Share Posted January 25, 2005 You have broken or burned pistons. 25's are fragile and won't tolerate much detonation. 90% of the time with RB's, #6 is the first to go. Are you still running the stock turbo and piping? If so, the oil coming out of the BOV could be from the crankcase vent into the turbo inlet. If it's on the right side of the engine compartment, it could also be from the dip-stick being blown out. I am still running the stock turbo and all the stock piping, including the stock SMIC. Where does the crankcase vent to the turbo inlet and how would that have happened?.....would there be any other damage to the block if that was the case? Quote Link to comment Share on other sites More sharing options...
tyson Posted January 26, 2005 Share Posted January 26, 2005 I would really just pull the head and start from there, mess with the other stuff later. You have lost compression, either way the head has got to come off...Within seconds of having your head off you should find out whats wrong. Speculating sucks, its either going to be cheap or expensive, and there is really only one way to find out. Quote Link to comment Share on other sites More sharing options...
cheftrd Posted January 26, 2005 Share Posted January 26, 2005 I am still running the stock turbo and all the stock piping, including the stock SMIC. Where does the crankcase vent to the turbo inlet and how would that have happened?.....would there be any other damage to the block if that was the case? If you look at the stock air inlet to the turbo, there is a hose that goes to the cam cover (unless it's been modified). When a piston lets go, the crankcase gets pressurized and blows oil out and into the turbo compressor inlet. Yasin, It's not that they won't make good power in the hands of a good tuner, they just have no tolerance for knock at elevated boost levels; same goes for the stock 26. If you are running up the boost to around 1.5, 1 bad pull with a hard knock can kill it. The ring lands give up quick. Only shooting 25psi of compression says that #6 is probably suffered a severly burned piston, probably on the intake side. Quote Link to comment Share on other sites More sharing options...
DETurbine Posted January 26, 2005 Author Share Posted January 26, 2005 Thanks for the reply guys. I am sure it is a piston that gave out (#6), but I have a feeling that I cracked the rest of the ring lands on all the other five. Same thing happend to my friends RB26. I just hope that a build up of pressure did not get down into my crank case and cause damage to anything else. I went over there last night to check out a few things and checked the dipstick and there was no oil that was shot out of it, so hopefully that is a good enough sign to show that there was not that much pressure in the case. Normally even when pressure it build up in there, it does no damage to the rods. I am going to get my rods machined and checked and also turn the crank as well. Really hoping that I will have to do nothing to the head. Just really sucks not knowing what damage it really did and am not going to know for at least another 3-4 days. Oh well have waited this long, so a few more days is not going to hurt. Going to take me another 30min to pull the motor out (just the two mounts and tranny mounts left) then probably an hour to hour and a half to get my tranny off, motor on a stand and head and oil pan off as well, then will be able to see what went on. I will keep you guys updated, Zach Quote Link to comment Share on other sites More sharing options...
mjfawke Posted January 26, 2005 Share Posted January 26, 2005 Chef - Did not realize 25s were that fragile...I always thought they were very stout and could take the lashings.... Yasin Yes - strong motor, but the pistons will not tolerate any detonation. Quote Link to comment Share on other sites More sharing options...
Guest StreetVelocityGTR Posted January 28, 2005 Share Posted January 28, 2005 So what can be done if you do detonate what can you do will upgraded pistons take it or sould you take every precaution to prevent detonation Quote Link to comment Share on other sites More sharing options...
cheftrd Posted January 28, 2005 Share Posted January 28, 2005 So what can be done if you do detonate what can you do will upgraded pistons take it or sould you take every precaution to prevent detonation You should always take every precaution to avoid detonation. Forged pistons are good insurance in a 500hp RB. IF you have prolonged knock and burn a piston, it won't make a difference. However, forged pistons won't break ring lands like the stock cast pistons will. Quote Link to comment Share on other sites More sharing options...
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