1984 2F cylinder #3 compression loss (1 Viewer)

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I have a 1984 fj60 with a 2F motor. I personally desmogged 6 months ago but had intermittent vacuum loss over the last few months, so I decided to pull my HAC 2 days ago. Vacuum lines and Plugs are in alignment with JimC diagrams. Following this my vacuum stayed at about 17, really no different than before but the intermittent loss of vacuum stopped.

Then last night while I was driving to work, I lost significant power and the motor started running really rough. I checked my vacuum and I had quick switching from 15-17. I limped her home this morning and started troubleshooting.

I started pulling spark plug wires and identified cylinder 3 as the culprit (no change in my idle when pulled). I then replaced the plug since I could see spark. No change with new plug. After all that, I got a compression gauge and found no compression in cylinder #3. I spoke with my local guy that I trust completely (Boozer’s Cruisers) and he is planning to do a cylinder leak down on Monday. I’m hoping that since its complete loss of pressure I’m dealing with an exhaust valve that’s stuck open.

I’d like to get an idea of what I’m looking at with regards to range or price for that kind of repair. I assume that while he’s that deep in the motor we will be replacing the head gasket and might as well do all the valves? What else could it be and cost? Any chance I blew the piston ring, and how much more would that be? Thanks in advance for any help.
 

MoaByte

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Sorry to hear that. I got low compression on #4 with the came vacuum readings. However mine runs pretty well.
 

MoaByte

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I hope for your sake it's a top end issue. If it's a ring you are on track for an overhaul.
 

OSS

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Statistically the problem likely is "just" a warped #3 exhaust valve caused by the valve overheating. Very common and pretty much expected for a high mileage 2F. I'd go so far to say that at 2F that hasn't burnt valves before 200,000 miles is a rarity.

Don't go down the "what if I'm F;:*ed mental rabbit hole. It's probably just a leaking valve. The cylinder head will have to come off for sure, then the problem (whatever it is) will be easy to identify
 
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Statistically the problem likely is "just" a warped #3 exhaust valve caused by the valve overheating. Very common and pretty much expected for a high mileage 2F. I'd go so far to say that at 2F that hasn't burnt valves before 200,000 miles is a rarity.

Don't go down the "what if I'm F;:*ed mental rabbit hole. It's probably just a leaking valve. The cylinder head will have to come off for sure, then the problem (whatever it is) will be easy to identify

Thanks OSS. I appreciate the sage advice. For once I hate the weekend because it means I’ve got to perseverate on this until Monday. I’ll try to keep my mind out of dark places.
 

MoaByte

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Yes thanks @OSS. The prospect of pulling the head instead of a ring job is something to smile about. I feared the worst even though I'm at 116,000 miles. That valve likely would be fine if I had followed the recommended valve lash adjustment schedule.
 

DFXR

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I know we’re still just speculating about the valve. But I just swapped out my head for a rebuilt one (head gasket blown btw 3 and 4) in my driveway. It’s not that bad of a job, even for an idiot like me with basic tools. If you’re desmogged, some of the most tedious work - removing and keeping track of the emissions stuff, and then getting it all back in order - is already done.

Doing it yourself, you could probably keep it around $1k with the machine work, various gaskets and new hardware for the manifold. I spent a few hundred more but I bought a “ready-to-go” head from the machine shop in an attempt to save down time.
 
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I know we’re still just speculating about the valve. But I just swapped out my head for a rebuilt one (head gasket blown btw 3 and 4) in my driveway. It’s not that bad of a job, even for an idiot like me with basic tools. If you’re desmogged, some of the most tedious work - removing and keeping track of the emissions stuff, and then getting it all back in order - is already done.

Doing it yourself, you could probably keep it around $1k with the machine work, various gaskets and new hardware for the manifold. I spent a few hundred more but I bought a “ready-to-go” head from the machine shop in an attempt to save down time.
My mechanic says it is definitely a burned valve. They’re going to pull the head tomorrow and get it over to a machine shop. I assume standard practice with this kind of thing would be to replace all the valves? Anything else other than having the head milled?
 

NeverGiveUpYota

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My mechanic says it is definitely a burned valve. They’re going to pull the head tomorrow and get it over to a machine shop. I assume standard practice with this kind of thing would be to replace all the valves? Anything else other than having the head milled?
Valve seals while they are there, possibly cut new seats. Those would be worthwhile minimums. Don’t get new springs. They are pretty stout and should be fine. Roll the push rods on glass just for your own piece of mine abd make sure they are flat. You can just replace one if not. I had to. Buy the Toyota head gasket. Possibly new headbolts too.
@TRAIL TAILOR sells new OE Japanese valves, or used to. They are beautiful and less than Toyota.
 
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As follow-up, I had a blown head gasket but valves all look good. Apparently the rupture was between #3 and #4, and if I had kept checking compression after #3 I would have found virtually no compression in #4 as well. The good news is my mechanic (Boozer's Cruisers in Birmingham) says the cylinders look clean and doesn't see any other major issues. No need for a full rebuild anytime soon. The head is at his mill guy now. Here's some pics for any interested. Should be back up and running by the end of the week or early next week.

IMG_6034.JPG


IMG_6035.JPG


IMG_6036.JPG


IMG_6037.JPG
 

Seth S

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Ask them to replace the oil galley plug in the cylinder head while they are working on it...if it hasn’t been done yet.

 
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