Engine Rebuild

Troubleshooting

After noticing that boost began to not hold well to redline (set to 14-15 psig, and falling to 10-11 psig by redline, whereas previously it had held ~16 psig to redline) despite having 13g's and 550 injectors, I began to do some troubleshooting. I checked for any obvious boost leaks, but found none. I attempted an intake pressure test, however I could not get any pressure to build, but I also did not notice any external leaks (I was using a very small air compressor though). I opened the oil cap (there was oil leaking around it) and found that there was positive pressure on the crankcase. I checked the PCV and it was ok (can blow through it going away from the crankcase, and could not blow through it toward the crankcase). I then blocked off the crankcase ventilation (both of them) to ensure that it was not the cause of the positive crankcase pressure, but I still could not build pressure in the intake, and there was still positive crankcase pressure.

At this point, after doing some research on 3SI, I determined that there were three potential causes: 1) valve stem seals leaking, 2) excessive blowby from pistons and/or piston rings and 3) oil seals on a turbo leaking. I then started the car, and there was no smoke immediately, which indicates that it is probably NOT valve stem seals, so number #1 possibility from above is eliminated (at least as a primary cause).

After a couple of minutes, it started to smoke a moderate amount (white/gray with only a hint of very very light blue. no smell of oil, coolant, or anything else abnormal). There was no change in the color of the smoke with revving, only an increase in the amount. I opened the oil filler cap while the engine was running, and very minimal air coming out. I checked the intake hoses after the turbos, and there was no oil in them, so therefore there is no turbo oil seal leak on the intake side of the turbos. Therefore #3 possibility from above is eliminated because if it is not leaking to intake side, then pressure is not going from intake side to the crankcase. However, oil could be leaking to the exhaust side only and causing exhaust to smoke, but it doesn't explain crankcase pressure.

So, that leaves #2 as the only logical explanation, however I wanted to verify it. I had noticed a slight consumption of oil (oil is not going to the intake side, so it has to be into combustion chamber, or exhaust side of turbo), and a slight gas smell from oil (this suggests that the oil loss is into combustion chamber). However, it had been a while since an oil change. I removed all six spark plugs, and they looked normal: white powdery on end, and electrode is gray to black powdery (no oil).

I did an oil change and there was a slight gas smell, and it was slightly thinner than normal and dark brown to black color. (Again, it was past due for an oil change). After the oil change, the exhaust still smoked, with the same characteristics as previously mentioned.

After the oil change, the intake pressure test was repeated (with crankcase vents blocked), and pressure still was on the crankcase.

Finally, I resorted to purchasing a compresion tester as it was going to be the only definitive way to determine if there was a problem with the pistons and/or pistons rings. The results were as follows:

Compression test results
Cylinder	Cold (psig)	Hot (psig)	w/oil (psig)
1	154	160	-
2	-	145	165
3	-	140	155
4	-	160	-
5	-	160	-
6	-	160	-

The factory service manual specifications are a standard of 156 psig with a lower limit of 115 psig, however there is also a note that says that there should be a difference of no more than 14 psi between the highest and lowest cylinder. So, all of my cylinders are well above the lower limit, but there is a difference of 20 psi between the highest and lowest cylinders, which is greater than the limit of 14 psi.

I tested one cylinder cold just to see what kind of difference there would be between a cold engine and a warm engine (factory service manual states to test the compression with the engine warm. ) Also, it suggests adding a few drops of oil to any cylinder which has low compression and then repeat the compression test. If the compression is raised, it suggests that the the piston rings are worn (or the cylinder walls). That was the case with cylinders two and three, where the compression was raised to within 5 psi of the other cylinders once oil had been added.

I would guess that many people have engines with a difference such as this and continue to run it without a catastrophic failure and it would run "just fine", however I did notice a decline in performance, so I decided to rebuild the engine (at 112,460 miles). (Disassembly pictures)

Reassembly

For the rebuild, I used Ross 93mm forged pistons with Total Seal piston rings. I used Clevite 77 Trimetal main and rod bearings (stock size). The engine was balanced and the bottom end was assembled by JM Racing in Lafayette, Indiana. The heads were rebuilt by Capitol Motors in Corydon, Indiana. Third generation lifters were also installed. In order to accomodate the larger diameter pistons, I used head gaskets from a 6G74 Montero engine. They are the same metal style as the stock gasket but not as thick, so I used two gaskets per side to make it approximately the same thickness as the stock gasket.

While the engine was removed, I took the opportunity to install JPDC poly motor mounts. Also, I had a spare EGT probe, and so I had the rear manifold tapped and added an EGT probe to it. I will make use of it later, when I get another EGT gauge. A Darkside Racing Lightweight Pulley was also installed during the reassembly. I also did the throttle body coolant bypass mod. I also replaced the fuel supply line with the Ek2 Development Fuel Supply Line and the fuel rail end loop with the Ek2 Development Fuel Rail End Loop. I also replaced almost every gasket throughout the engine during the rebuild, and performed the 120k tuneup (new water pump, timing belt, tensioner, accessory belts, thermostat, oil pump, etc). I'm certain that the new gaskets won't hurt, because many of the old gaskets were very brittle. I also decided to change the transmission fluid to Pennzoil Synchromesh based on the positive results of many users on 3SI.org.

During reassembly, I encountered a few issues. When the coolant system was filled, there was a leak near the timing belt area (thankfully I had used pure water to test for leaks so it didn't make as bad of a mess). What I found was that when I reinstalled the coolant blockoff plates on the driver side of the block, I failed to remove all of the old gasket material and I did not use sealant, and so it leaked. Also, I used the fuel pump relay feature on the pocketlogger to avoid cranking the engine, and found that I had a fuel leak on the outlet of the fuel filter where the Ek2 Development fuel supply line connected. After fuel lines have been broken, I would definitely recommend that the battery is placed outside of the vehicle and jumper cables are used to test the integrity of the lines. After inspection of the fuel line, I discovered that the banjo bolt fitting did not line up properly with the notches on the top of the fuel filter (it is a Wix fuel filter from NAPA). The large size of the fitting caused the line to be pushed crooked, and not seat onto the top of the fuel filter. To correct this, a couple of the tabs on the top of the fuel filter were broken off with pliers, and the edges were hammered flat. I am not aware of anyone else who has had this problem, but I could not find a way for the line to fit without leaking otherwise. (I tried several different positions and angles, and it leaked multiple times). It appears that the stock fuel filter does not have the same notches, and therefore would not be a problem with an OEM fuel filter. After the initial restart, one of the accessory belts was slightly crooked, and we found that the Darkside Racing lightweight crank pulley was not mounted flush; it was wobbling. When it was removed, we found that the alignment hole had been knicked (apparently during the initial installation), and that the pin was not appropriately lined up with the index hole on the pulley. It was carefully reinstalled paying particular attention to ensure that the pin was lined up with the index hole and that the pulley was completely pushed onto the crankshaft before tightening the center bolt. (I believed that I had tightened the center bolt before the pin was fully inserted into the index hole, causing it to not line up correctly.)

Other than those couple of minor issues, the reassembly went well. After buliding oil pressure, the crankshaft and camshaft sensors were plugged in, and the car fired up almost immediately. So far (low boost), it seems to be driving well.