Replaced head gasket and still have low compression. - Toyota Nation Forum : Toyota Car and Truck Forums

atikovi · 10-31-2006, 04:25 PM

This 86 Camry I bought was blowing out white smoke when warmed up and I found low compression in the center cylinders so I assumed it was just a bad head gasket. I bought a head gasket set, got the head off, did some minor clean-up, lapped the valves, new stem seals etc. and put it back on the engine. After tightening the head down I did a leak down test and found the same excessive leak down on the two center cylinders. Holy crap! Luckily I didn’t assemble everything back together so in 5 minutes I got the head back off. Took it to a machine shop which checked the head and said the valves were tight and there was no warpage and that the problem is probably in the rings. I’m trying a crude test by setting the pistons at the same level and filling the bore with transmission fluid and seeing if those 2 cylinders have a greater drop in the level of fluid than the others after 12 to 24 hours. In the mean time I’ll contemplate replacing the rings. Anyone know if you can just drop the oil pan and unbolt the rods from the crank to shove the piston up out of the engine, or will the engine have to come out of the car?

white90dx · 10-31-2006, 05:22 PM

You can do it all in the car... its one hell of a way to build a motor, but it is possible. Good luck! (and now you know to check the rings

)

-Charlie

fredk · 10-31-2006, 06:43 PM

ive done it many times, get a helper up top and scuff up the cylinders with some fine sandpaper and use a good ring compressor and new bearings

atikovi · 10-31-2006, 06:49 PM

Good to know I don't have to pull the engine. Should I get standard size or oversize rings? The car has 125K miles. Should I do all 4 cylinders or is it enough to do just the 2 bad ones? Why replace the bearings if they didn't make any noise?

atikovi · 10-31-2006, 07:03 PM

8 hours into leakdown test:

The 2 center problem cylinders already clearly show more leakage than the good outer cylinders. At the start, transmission fluid was all the way to the top of the cylinders at the rear. (Remember engine is tilted backwards)

Anyone know what that brass colored band is at the top of the cylinders?

IvanHoe · 10-31-2006, 07:12 PM

Nice pic and good way to test them! If I were you, I would replace all of the piston rings and NOT just the 2 bad ones!

white90dx · 11-01-2006, 12:50 PM

Quote:

Originally Posted by atikovi

Anyone know what that brass colored band is at the top of the cylinders?

That's just where the rings don't scrape the cylinder walls clean.

What's funny, in my experience, most of the time when a motor has low compression it is a ring problem (performance motors, mostly). You will generally have some other sign if it is the head gasket (coolant in oil, oil in coolant, boiling/dissapearing coolant, etc)

-Charlie

IvanHoe · 11-01-2006, 01:06 PM

Quote:

Originally Posted by white90dx

What's funny, in my experience, most of the time when a motor has low compression it is a ring problem (performance motors, mostly). You will generally have some other sign if it is the head gasket (coolant in oil, oil in coolant, boiling/dissapearing coolant, etc)

-Charlie

+1

***toyomoho*** · 11-01-2006, 06:57 PM

If the bearings are OK, they can reused. Check for wear and keep track of the exact location they came out of. The other option is a rod bearing set, very low cost if you shop around.

Suggest you buy or rent some kind of drill powered cylinder hone or glaze breaker. You want a nice crosshatch finish on the cylinder. Flush out the cylinders when you are through but plug the crank oil holes first.

For ring size, you will need to measure the inside bore of the cylinder. A service manual should state when standard or oversize rings are required. There may be oversize rings available that fit a standard size piston. Talk to the machine shop that did the head, they should know about this.

Since you will have all the tools and engine apart. Doing the other two cylinders is not that much more work. Buy a complete engine set of rings.

atikovi · 11-01-2006, 07:16 PM

I bought both a set of standard size rings and bearings and some Plastigage to check the clearance. Car only has 125k miles so it shouldn't have enough wear to go oversize. I do have a cylinder hone. What should the ring end gap be?

Toysrme · 11-01-2006, 07:24 PM

Rings.

fredk · 11-01-2006, 09:23 PM

stagger the ring gaps, scuff up the walls a little, put new rod bearings in it and be done with it, change the mains if you want

***toyomoho*** · 11-02-2006, 06:36 PM

Ring gap for a 2S-E is below:
Top compression 0.0110 - 0.0197
Bot compression 0.0079 - 0.0177
Oil control 0.0079 - 0.0311

Piston clearance 0.0006-0.0014

Connecting rod bearing clearance 0.0009 – 0.0022

atikovi · 11-02-2006, 07:46 PM

Thanks for the specs. I found the center two pistons had chunks of the ring lands broken out. Bought 2 new pistons and got them back in but when I torqued down the #3 rod I can't turn the crank with a wrench anymore, it's too tight. Plastigauge shows it to have .0015" clearance. I'll have to take that piston and rod out tomorrow and take a closer look but any idea what would cause that?

fredk · 11-02-2006, 07:53 PM

will it turn with the other 3 rods hooked up?