Need advice regarding low compression/white smoke (1 Viewer)

[ginmtb]

I posted this on my build thread but figured I should post a new thread to get more feedback from the experts. I recently did a road trip for the Cross Country Expedition (500 miles) and overall my cruiser performed well 15MPG!!! I noticed going down a long, steep decline (2 miles at 15%-20% grade, 2nd gear 25MPH max) it was pumping out some good white smoke. Once I got to the flat road all was fine.

So I decided to do a compression test to see if that could help with the diagnosis of the white smoke (and to get a baseline of where my engine was - btw, '74, 1.5F, ~139K miles). I checked my oil and it wasn't milky (perhaps a little overfilled) and I also checked the anti-freeze and that seemed fine too - full in the radiator and at the same level in the overflow tank. Here are the results of my compression test (car was warmed up FYI):

Dry test #1
132-135-137-129-105-150

Dry test #2
140-137-140-135-117-151

I decided to only wet test #5 since all the other numbers seemed pretty good. The result was 106, close to the initial low reading. What should I do next? Been trying to do some research here but man there is almost too much info. Signs don't seem to point to a blown head gasket. Exhaust valve gone bad? Valve out of adjustment? My valves were adjusted just over 2 years ago at Georg's @orangefj45 shop - perhaps I need to check/adjust them again? Not sure what the service interval is - have probably only put on 2K miles since then, maybe a little more. Also, my spark plugs have a little fouling, as in dark carbon, but no sludge.

Appreciate the help!

 

[Jetlander]

Sounds like a head gasket.

 

[ginmtb]

Sounds like a head gasket.

Hmm... It doesn't seem like it based on the symptoms but I've been wrong before. I do have a tester so perhaps I should use that and see what happens.

Eight Signs of a Blown Head Gasket

The signs of a blown head gasket can be subtle. Here are eight of the most common indications that your head gasket has failed:

1. An external oil or coolant leak at the seam between the engine block and cylinder head is a sign that you have a head gasket failure or a cracked block. On disassembly, check for cracks and cylinder head warping. - DON'T SEE THIS
2. Cylinder misfire is another sign of head gasket failure, especially if the breach is between two cylinders on the same head. Cylinder compression and leakdown tests can localize the leak for scrutiny on disassembly. - I'M NOT HAVING MISFIRES, AND USUALLY IF THE HEAD GASKET FAILS BETWEEN TWO CYLINDERS DON'T TWO OF THEM HAVE LOW COMPRESSION? HAVEN'T DONE A LEAK DOWN TEST.
3. Misfire on startup, if accompanied by a puff of white exhaust, could indicate a leak from the cooling system into the cylinder. - DON'T SEE THIS
4. Overheating is one of the less-obvious signs of a blown head gasket. Depending on the severity of the leak, you may see bubbles in the overflow tank, indicating that the cylinder is leaking into the cooling system. - NO OVERHEATING, DON'T SEE BUBBLES
5. Blue exhaust smoke could also indicate head gasket failure, but so could worn rings, valve stem seals or a faulty PCV system. - DON'T SEE THIS
6. Discolored fluids are more subtle signs of a blown head gasket. - DON'T SEE THIS
7. Coolant-contaminated oil takes on a frothy consistency; it’s like finding a latte under your oil cap or in the valve covers. - DON'T SEE THIS
8. Oil-contaminated coolant forms a mayonnaise-like film, which you might find on the radiator cap or in the overflow reservoir. - DON'T SEE THIS

 

[Solace in Solitude]

If you haven't seen this THREAD... good info, beginning at post #4... Also, good spark plug diagnosis HERE

You had the throttle wide open for the compression tests... Right?

I'm no expert, I just like to dress up and pretend... But, before removing the head, I would adjust the #5 valves and retest dry compression, with throttle wide open. Then a couple squirts of oil in #5 and retest wet compression, with throttle wide open.

 

[ginmtb]

If you haven't seen this THREAD... good info, beginning at post #4... Also, good spark plug diagnosis HERE

You had the throttle wide open for the compression tests... Right?

I'm no expert, I just like to dress up and pretend... But, before removing the head, I would adjust the #5 valves and retest dry compression, with throttle wide open. Then a couple squirts of oil in #5 and retest wet compression, with throttle wide open.

Thanks Danny! Yes, throttle wide open (assuming that means gas pedal all the way down - which I didn't do on test #1 hence my retest).

I need to get a set of feeler gauges... And try to decipher all the valve adjustment info too. I recall reading a thread by @Pin_Head which said to keep things simple and do a GO/NO GO test of the valves while running. If NO GO, too tight and needs adjustment. If GO then check to ensure gap isn't too big by going up in size 0.002. This is it - First valve adjustment on my 78 FJ40 ...

Good info on the spark plugs. I had intended to search for that so thank you! This sounds like my condition:

Appearance & Symptoms: Dry fouling (top) appears as sooty, black build-up. Wet fouling (bottom) has a wet, sometimes oily appearance. Both conditions can create poor starting and misfiring.

Dry fouling, or carbon fouling, is often caused by an overly rich condition, and the problem may lie with your air cleaner (clogged) or carburetor. Other possible causes could be low compression, vacuum leak, overly retarded timing, or improper spark plug heat range.

 

[Solace in Solitude]

Yes, pedal to the metal while testing.

@FJ40Jim told me to run a ‘hot’ plug and suggested “Denso W14EXR-U”.

For feeler gauges, I use ‘Lisle 68150 Go-No-Go Feeler Gauge’. The top 1/2” or so (of each blade) is the labeled size (go). The next portion of each blade is the next size up (no-go). If the “go” tip fits correctly, good. If the “no-go” fits, no good.

The FSM says to test/adjust valves, with engine hot, throttle open and engine running.

I’ve read a lot of comments... everyone has their own ideas, regarding valve adjustment and the need to adjust the lash of moving valves.

I don’t know the best method... I check the lash, with the engine running. Then shut it down and adjust those found to be out of tolerance... I’m simply not able to properly adjust moving valves and have found myself almost hypnotized at times.

Check again, engine running, after adjustment.

 

[ginmtb]

Ok ordered the spark plugs. I’ll try and get to the valve in the next day or two. We’ll see... mechanical stuff still scares me some. Wish I could watch someone do it once before I try it.

 

[Solace in Solitude]

There’s a nice discussion HERE...

There is info and several videos available HERE. They all offer insights, but are (obviously) not professional quality videos.

I’m vertically challenged, it’s hard to reach the rockers, with both hands, without face planting in them.

But, if you can easily reach the rockers and have certain ninja skills, you will find it easy to check the valve lash, while the engine is running.

Make sure the engine is at operating temperature and write down your results.

Then shut her down and adjust those out of tolerance.

Start her back up, get her hot and check again.

 

[cruiserkev]

Cracked head may be an unfortunate possibility. I had a hairline Crack above my #5 cylinder back in the 90s that took months to diagnose correctly. I would get a little white smoke on startup but had no other performance issues. Combustion pressure was entering the cooling system and eventually burped out into my coolant overflow tank several minutes after shutting off the engine. I had to use a special tool that attached to my radiator and analyzed my coolant to figure this out. Hope this is not the case with your engine, I had to replace the head on mine. Good luck!

 

[ginmtb]

Cracked head may be an unfortunate possibility. I had a hairline Crack above my #5 cylinder back in the 90s that took months to diagnose correctly. I would get a little white smoke on startup but had no other performance issues. Combustion pressure was entering the cooling system and eventually burped out into my coolant overflow tank several minutes after shutting off the engine. I had to use a special tool that attached to my radiator and analyzed my coolant to figure this out. Hope this is not the case with your engine, I had to replace the head on mine. Good luck!

I hate to like this reply but understand that it could be a lot of things - hopefully this isn’t it. Fingers crossed. Will do the valve adjustment and hope that solves my issue. I just got a valve adjustment lessson from a co-worker who is a big time car guy (has a shop at his house and does a ton of work for paying customers) and feel like I understand the process better now. Thanks for sharing your experience sorry that was yours.

 

[C6H12O6]

I'm not thinking head gasket quite yet, either. The lack of a change dry vs. wet on the compression definitely supports your looking at the head, but I'm thinking valvetrain for the root of your problem. I would get a decent feeler gauge set and check valve clearances. Not much mechanical scariness simply to check clearances. Just don't drop the feeler gauge into the head, and you really can't hurt much. If you find something out of whack, adjust and recheck the compression. One of the valves on #5 is probably set a little tight and isn't closing all the way. The only weird thing is that the valve lash usually gets sloppier over time, not tighter. Hmm...

If everything checks out, you need to run a leakdown test. This will pretty much tell you where the compression is escaping. It would be great to have help, but it's not too bad if you have all the tools. This is usually pretty conclusive. Where things get tricky is when everything checks out and you're still losing compression in the head somewhere. Could be a cracked head, but check the easy stuff first. Like the old saying goes, when you hear hoofbeats, think of horses not zebras. The only thing that makes me worry, is that valves usually <edit: see last sentence of above paragraph.>

 

[ginmtb]

I'm not thinking head gasket quite yet, either. The lack of a change dry vs. wet on the compression definitely supports your looking at the head, but I'm thinking valvetrain for the root of your problem. I would get a decent feeler gauge set and check valve clearances. Not much mechanical scariness simply to check clearances. Just don't drop the feeler gauge into the head, and you really can't hurt much. If you find something out of whack, adjust and recheck the compression. One of the valves on #5 is probably set a little tight and isn't closing all the way. The only weird thing is that the valve lash usually gets sloppier over time, not tighter. Hmm...

If everything checks out, you need to run a leakdown test. This will pretty much tell you where the compression is escaping. It would be great to have help, but it's not too bad if you have all the tools. This is usually pretty conclusive. Where things get tricky is when everything checks out and you're still losing compression in the head somewhere. Could be a cracked head, but check the easy stuff first. Like the old saying goes, when you hear hoofbeats, think of horses not zebras. The only thing that makes me worry, is that valves usually

Valves usually? Don’t leave me hangin’!!!

 

[C6H12O6]

Oops. I moved it to the paragraph above.

They usually get looser on the valve lash, leading to tighter valves, not the other way. I would think if Georg adjusted them, they were probably correct. It would be weird for them to tighten up over time and leave the valves open. Lash could be fine and something is causing a valve to stick open, I suppose. Would probably be doing it all the time, though. See what I mean? Weird.

 

[ginmtb]

Oops. I moved it to the paragraph above.

They usually get looser on the valve lash, leading to tighter valves, not the other way. I would think if Georg adjusted them, they were probably correct. It would be weird for them to tighten up over time and leave the valves open. Lash could be fine and something is causing a valve to stick open, I suppose. Would probably be doing it all the time, though. See what I mean? Weird.

Yes that makes perfect sense thanks! Would be weird to become tighter...

 

[Mace]

You absolutely can see the valves tighten over time creating a situation where the valve never closes fully.

Stretched valves can do this as can hammering the exhaust valve into the seat.

I'd check with the motor warm and not running. But even a cold check will get you in the ballpark..

 

[Malleus]

Have you tried UV dye? This will show a crack. A Blackstone oil analysis will tell you if you have coolant in your oil. Both are significantly cheaper than a new head.

 

[ginmtb]

You absolutely can see the valves tighten over time creating a situation where the valve never closes fully.

Stretched valves can do this as can hammering the exhaust valve into the seat.

I'd check with the motor warm and not running. But even a cold check will get you in the ballpark..

Good to know thank you! Lots to learn still... I’m no mechanic!

 

[ginmtb]

Have you tried UV dye? This will show a crack. A Blackstone oil analysis will tell you if you have coolant in your oil. Both are significantly cheaper than a new head.

I have the kit if the valve adjustment doesn’t fix the problem I’ll go that route and test. Thanks!

 

[C6H12O6]

Stretched valves can do this as can hammering the exhaust valve into the seat.

Gotta love 'MUD. Didn't think about stretched valves. Usually more of an issue on high-revving, high-HP engines, but I suppose it's possible. Especially if that #5 exhaust valve had been not seating properly before it was adjusted properly by Georg. Tough life for those exhaust valves.

 

[mrboatman]

You could also try compressed air in each cylinder with the both valves closed. That will tell you if the valves are not seating or how much blow by you have
JP