Compression Issues

[Vicente Madrid]

Look at tuneup stuff first - did your timing slip - that sort of thing. It's unlikely the head or engine suddenly developed major internal problems without warning. Post your actual compression numbers here, before you pull the trigger on a rebuild.

I couldn't find the numbers from before so I just finished a second test now. It read,
90, 80, 0, 0, 80, 90. Much worse than a few months ago. I'm not sure if the 0 are accurate it made a different sound for those cylinders, but it may have be been air seeping through somewhere.

I'm not too sure how to check if the timing slipped. I did a little bit of research, the engine starts up really easy. Normally with what seems like less than one rotation.

Should I still check the valves or just stay looking into a rebuild. (I'd imagine these readings to be pretty bad)

 

[Vicente Madrid]

I also did a wet compression test and got, 120, 120, 10, 10, 150, 100.

 

[SteveH]

Pull the valve cover and check your valve clearances (especially on the low reading cylinders). Remember to set the engine to TDC, then rotate crank, according to the usual procedure (described in the Haynes and factory manuals). The more you know (before you go to a mechanic), the better.

 

[2mbb]

two adjacent cylinders with low compression can indicate a head gasket failure. That could also be why it sounds different. This is a failure that will happen suddenly, too.

 

[Vicente Madrid]

Pull the valve cover and check your valve clearances (especially on the low reading cylinders). Remember to set the engine to TDC, then rotate crank, according to the usual procedure (described in the Haynes and factory manuals). The more you know (before you go to a mechanic), the better.

I checked the clearances and had quite a bit off. Really, the two reading 0 weren't off by much at all though. I did a compression test on those same two and still got 0.

But, I have noticed a a significant difference in the power of the engine, so I'm definitely happy I did this. Thank you!

two adjacent cylinders with low compression can indicate a head gasket failure. That could also be why it sounds different. This is a failure that will happen suddenly, too.

I read about that in the Haynes, I was unsure if this was the cause of the issue since I don't seem to have any water in my oil.

If I were to take off the head would I be able to tell if the gasket went out prior? And, is there any way of telling at that point whether the head needs to be rebuilt?

I greatly appreciate everyone's input and knowledge. You all deserve this.

 

[FJ62NY]

Compression is pretty easy and you can rent the tool from your local auto parts store like OReilly or Autozone. Get someone to help you turn over the engine and then write the numbers down yourself. If you want that is...
If you are not seeing smoke, idles fine, starts easy and has decent power then the first shop may be taking you for a ride.
The gas smell could also be coming from the rear. Take the back panel off where the filler neck is and see if you see any gas sloshing around in there. Also when you take the gas cap off do you hear/feel a large WHOOOOSH?

Is it normal that when I go to fill gas and take the gas cap off theres that whoosh? Is that a bad sign for something? TIA

 

[gregnash]

Is it normal that when I go to fill gas and take the gas cap off theres that whoosh? Is that a bad sign for something? TIA

Not a bad sign of anything catastrophic happening, it just means that your gas tank is pressurized. If the "whoosh" happens for an extended period of time after taking the cap off, like several seconds, that means your system is not purging the pressure in the tank which can lead to issues. This normally has to do with the charcoal canister and/or the gas cap not working properly. ONLY GET AN OEM gas cap as it has a small relief valve built into the cap that lets some pressure out... Look up the charcoal canister hose swap to see if that solves the whoosh.

 

[2mbb]

I read about that in the Haynes, I was unsure if this was the cause of the issue since I don't seem to have any water in my oil.

The head gasket technically can fail between two adjacent cylinders or between one cylinder and the water jacket. Only the latter will cause water to end up in the oil. You can seen in this picture from the FSM how close the cylinders are and how thin the gasket is between cylinders 3 and 4. You can probably check by taking out both spark plugs and blow compressed air into one cylinder. If it comes out the other, that's an indication that gasket between the cylinders is blown (this is similar to a cylinder leakdown test).

 

[Vicente Madrid]

The head gasket technically can fail between two adjacent cylinders or between one cylinder and the water jacket. Only the latter will cause water to end up in the oil. You can seen in this picture from the FSM how close the cylinders are and how thin the gasket is between cylinders 3 and 4.

View attachment 1456452

That makes sense. I went ahead and took the cylinder head off, I figured I'd need to rather it was the gasket or not. It most definitely was, it was completely missing between those two cylinders.

I'm going to, check for cracks, for warping, and the cylinder seating. Hopefully the gasket is all that went wrong.

Thank you for the knowledge!

 

[SteveH]

it was completely missing between those two cylinders.

gotta like something as obvious as that!

 

[morganism]

that sounds like a stuck open EGR, if you stil have one on a de-smogged...

 

[Vicente Madrid]

I think that may be adding to it. As I've started this job I've noticed a lot of lines that should have been plugged or directed to something, but weren't.

I tested the valve compression and had a little bit of inconsistency, I'm having the valves lapped and the seats checked. As I wait for this to be done I'm going to go through the de-smog guidelines and see if there's anything else they forgot to do.

P.S. - I'm sure everyone knows, be very mindful of the mechanics you take your cruiser too.

 

[FirstFJ60]

I think that may be adding to it. As I've started this job I've noticed a lot of lines that should have been plugged or directed to something, but weren't.

I tested the valve compression and had a little bit of inconsistency, I'm having the valves lapped and the seats checked. As I wait for this to be done I'm going to go through the de-smog guidelines and see if there's anything else they forgot to do.

P.S. - I'm sure everyone knows, be very mindful of the mechanics you take your cruiser too.

Any updates on your thread?