Compression Test Results - What can they tell me? (2 Viewers)

[thecapedcapper]

After owning the truck for a bit over a year I finally compression tested my 332k mile 40th aniv. today. As as I know the headgasket is original and the engine has never been opened, although it was very well taken care of by the previous owner who put the majority of the miles on it. That being said I was pretty happy when almost every cylinder was between 170 and 180 with a dry compression test. #3 Peaked at 150 which isn't terrible but relative to the others isn't great.

Does this mean a headgasket should be in my future? Or that I should at least be very cautious? The coolant isn't murky at all and there's no telltale smoke or smell so I think I'm ok for at least the time being.

Additionally it does use a bit of oil and the (previous owner installed) catch can did fill up after about 2-3k although it is fairly small. This tell me that unsurprisingly my valve stem seals are probably going, but given I don't generally daily the truck that's not the end of the world.

I'm thinking within the next year I should pull the head, have it checked and rebuilt (or buy a rebuilt head) and replace the headgasket and all the other seals while I'm at it. I've been shopping full engine rebuilds but with most being 170-180 I'm thinking that might be unnecessary? I really appreciate any thoughts from those that have been through this before. Thanks

 

[ppc]

You should have done a leak-down test to determine where the leak is on #3. It could be head gasket, leaking valves, bad rings, cracked head or a scored cylinder wall to name a few.

 

[robnicko]

with that mileage and being original id be pulling the head on it - valve stem seals would well be past their use by date in my opinion and the prime suspects for oil consumption

for #3 try putting some oil in the plug hole and see if it increases the reading - this would indicate rings however based on what you have described so far would be surprised if the case - sounds more like time to pull the head and refresh the top end using the original head if all is fine with it

do you know when the valve clearances were last checked?

 

[thecapedcapper]

with that mileage and being original id be pulling the head on it - valve stem seals would well be past their use by date in my opinion and the prime suspects for oil consumption

for #3 try putting some oil in the plug hole and see if it increases the reading - this would indicate rings however based on what you have described so far would be surprised if the case - sounds more like time to pull the head and refresh the top end

do you know when the valve clearances were last checked?

Great question about the valve clearance, probably never. Or at least it's been a long long time. It's good to hear other thought the same as mine. I should have checked #3 wet while I had the chance but didn't think about it. If nothing else I'll have to do that.

You should have done a leak-down test to determine where the leak is on #3. It could be head gasket, leaking valves, bad rings, cracked head or a scored cylinder wall to name a few.

Yeah.. I probably should have done that while I was at it but was thinking one thing as a time. I'll need to do it another day to see for sure

 

[Squeegee]

From one over thinker to another, I vote to leave it alone and go enjoy your life. She has over 300k, it’s hard to ask for more. When she starts letting the magic smoke out, then worry about a headgasket/ rebuild. If it’s not making coolant disappear or drinking massive amounts of oil, it’s probably just fine. So party on

 

[leonard_nemoy]

Don't fix if it ain't broke. Keep driving that bit**

 

[JoeW]

As others stated here, a compression test by itself doesn't offer much more than which cylinder to look at, but won't really give you much of an idea what's wrong unless you add oil and the number goes up. Leakdown would let you know WHERE that 30 psi is going. But like others have said, at that mileage, just rock it until it starts giving reason to dig further.

 

[SpenserAK]

Visual food for thought re: leakdown.

Compression test is on my list to get around to. I'm sure I will have the same reaction and questions if I find any cylinders to be off, but she runs and drives great currently.

 

[thecapedcapper]

Me, my wallet, and my precious free time all like what you guys are saying. I need an inspection so I'll have my shop do a leakdown test on that cylinder while it's there I think, and regardless maybe look into a head rebuild or rebuilt head.

 

[thecapedcapper]

After having the truck sit for a few days I was backing it out of the driveway earlier and there was a fair bit of white smoke.. and a bit of smell of coolant. Let it sit for a while and pulled the radiator cap, and from what I can see it's barely wet... so looks like the headgasket job got moved up. I'm thinking I should either get my head rebuilt or buy an already rebuilt one.