Discouraging Rebuild

[oldmansupra]

So here are my problems:

- bubbling noise from the back of the engine audible from inside the car.
- white/gray smoke coming from exhaust
- poor compression (however only 6 and 3 are low and bump back up after oil is added)

Now I know these are symptoms of the BHG, however it all doesn't add up. No gunk by the oil cap, and my car doesn't overheat. Also no cooling gushes out of the overflow tank. Also my motor was rebuilt with forged pistons, eagle rods, MHG and ARP studs. It's really frustrating to have these problems as I was pretty confident that my head gasket wouldn't blow after this.

Some things point to a BHG, but others points to blown rings. (oil in the intake manifold, poor compression on 6 and 3). Tomorrow I'm going to re-compression test the engine and see what's it currently at.

A possibility for the bubbling noise is that I recently had a coolant leak. I fixed the leak but my system could just have some bubbles in it. I'm going to drain it all and refill it to see if the noise goes away. Next step after that I guess would be to get the combustion test kit and see what color the fluid turns.

 

[honeydew]

Blown rings would be blue smoke. Oil blow by. Coolant may have bubbles in it if you can hear gurgling, flush and fill it.. White smoke means coolant in cylinders. 7M ? 5M?

How long have you been driving the new-ish engine? Do you drive it long enough to over-heat? Slow seep? Was the head and block milled perfectly for a MHG?

 

[JonnyZ(Socal)]

Ok when you say poor compression does that mean in all cylinders or in 6 and 3 only... If it's only 6 and 3 if they go back close to spec when you put oil then you have bad rings or they may have not seated properly due to not being broken in! And I believe that after a rebuild yo have to re-torque the head bolts after about 500 miles or so... Idk if this is the same for a MHG as I don't know if it compresses any more.

 

[Sparky33]

an easy test that sometimes works is also if you get a coolant pressure tester and start the engine with the tester on, check to see if there is more pressure than normal.

 

[stolensupra]

The bubbling noise can sometimes be caused by air bubbles in the coolant, more specifically traveling through the heater core. This can be alleviated by parking on a steep hill with the engine running (but not hot) because you'll want to take off the radiator cap to let the air out. There's tons of more specific info on this on the forums.

 

[jdub]

Air in the coolant system can cause the sound, but on a correctly routed and properly functioning system, you should never have to "burp" it. It will get rid of the air on its own. There is no need to drain and refill. If you want to assist the process, just cut the jiggle valve off the T-stat.

Just get a NAPA block tester and check for exhaust gas in the coolant.

There are several BHG modes - you do not have to have coolant in the oil with a BHG. A small leak will not cause coolant to overflow the bottle.

Low compression on one or more cylinders with white smoke point to a HG that did not seal. Most common causes:
- Block was not resurfaced
- Block/head was not resurfaced the the proper RA spec for the MHG used
- Improper torque and/or tightening sequence for the bolts/studs

It is possible the rings were not installed properly and are the cause of the low compression. Need detail on # miles, break-in method, and specifics on the block machine work (clearances, etc).

 

[oldmansupra]

So I compression tested my engine and the results were better then previously:
1. 138 psi
2. 140 psi
3. 140 psi
4. 145 psi
5. 135 psi
6. 140 psi

Also after letting it idle for longer the exhaust is definitely blue. It feels steamy when I put my hand up to it but that's subjective. Currently the AFM is hacked up (big hole in the electronics and not reading properly with my digital multimeter). I ordered in a MAF-T pro to replace it which should be in by the end of October or sometime in November. I'm now thinking the smoke is due to incorrect A/F ratios. After installing a new CPS I bought a timing light but haven't timed the ignition because the idle won't drop below 1500.

After removing the intake manifold and fuel rail I had coolant and fuel leaks on that side of the engine. I've fixed those but that's why I'm thinking air got into the system. After I get it plated I'm going to take it to the steep hill near my house and burp the coolant system.

A few of the spark plugs had a little bit of oil on them, also if I look down into the holes I can see oil. There was also oil in my intake manifold. My PCV system poured out oil when I removed it as well. The oil change place I last took it to filled it up past the full mark on my dipstick, could that cause excessive blow-by to my PCV, intake chamber and spark plugs? I'm thinking installing an oil catch can might help get rid of some of that oil.

Letting it idle for a bit this past week must have helped. The engine was a 88 JDM engine and I've installed a new engine harness, ECU and CPS. Now the rebuild was done by a shop, and the previous owner couldn't tell me very specific information that would been good to know. For the engine rebuild this is all he could tell me: Eagle pistons, Manley rods, ARP fasteners (torqued the correct amount), Port and Polish, 5 angle valve job, the intake has been match ported, metal headgasket. I really wish I had more information about the bore of the pistons, the thickness of the metal head gasket and how much was removed, and possibly what roughness average it was machined to. Also I have little information about how it was broken in, I imagine not great as it was his track car and had bigger injectors, a piggyback system, mk4 fuel pump, bigger fuel pressure regulator, among other things. When I bought it, it was freshly rebuilt with was I was told was 15, 000 kms on it. I drove it about 3, 000 kms since then.

The compression is steady across the board but I'm wondering if the low readings are due to the pistons, and ratio of the block removed compared to the thickness of the head gasket. I'm thinking of getting a leak down tester to further diagnose the engine. Still new to the 7m so I'm learning as I go.