2F Compression Check Result Questions (1 Viewer)

[bsang]

I have an 84 60 with a 2F at 150k miles. I bought it 4 years ago and have since put almost 20k miles.

I leak ALOT of oil and have to top off 5-6 quarts every 6-12 months or 3-5k miles. Because of the leaks, I'm never been sure if I was also burning oil.

I also go through ALOT of coolant, 1-2 gallons each time I top off oil. No coolant leaks

I figured maybe the head gasket was shot causing the coolant to go into the oil, so I did a compression test.

I am now doing an overhaul on the leaks, and planned on pulling the head to replace the gasket, however not sure what to think with these results:

1-2 revs / 3-4 revs / 8-9 revs

1 = 100 / 160 / 180
2 = 100 / 150 / 170
3 = 95 / 155 / 170
4 = 95 / 150 / 170
5 = 90 / 145 / 165
6 = 100 / 170 / 185

I was not expecting such clean results. I was just waiting for one or two of the cylinders to be exceptionally low.

Is this safe to say head gasket is good? Where is my coolant going?

 

[Seth S]

When you pull your dipstick is your oil black or clear? Or is it like chocolate milk?

If you were losing that much oil or coolant to a head gasket you would see clouds of blue or white smoke coming out the tail pipe.

Your compression numbers don’t show a head gasket but head gasket scan fail and result in just fluid leaks without loss of compression. If your oil looks like oil and no sign of the coolant and oil mixing then you could have lots of gasket and seal leaks for the oil. Maybe you have a bad rear heater line and it’s dumping coolant where you don’t see it.

 

[bsang]

Thanks for the quick reply.

The oil is pretty brown, and never notice a cloudy-ness to it. And nothing really noticeable from the tailpipe.

I am sending the oil to Blackstone for analysis, so I'll have to wait for the final results.

Truck will be up for a bit as I'm covering a lot of deferred maintenance- carb, trans, hubs, PS, A/C and more. May just pull the head "while I'm in there"

 

[bsang]

I can note that my coolant (mostly noticeable in the overflow tank) turns light milky brown.

 

[BGarcia88FJ62]

I can note that my coolant (mostly noticeable in the overflow tank) turns light milky brown.

Milky Coolant isn't a good sign and should be further investigated. Pressure test the cooling system?

 

[ceylonfj40nut]

If it does not look like a headgasket issue, check the integrity of your oil cooler as well. That is another part that has an oil water interface.

 

[Seth S]

If your oil is brown and your coolant is brown then the two are mixing together. The cheap answer is your head gasket failed and coolant is mixing with oil but your compression isn’t effected. The expensive answer is you have a cracked head.

 

[OSS]

The purpose of a compression check is to determine whether the head needs to come off to rebuild it. Since you've decided to pull the head, there's no point in trying to guess what the problem is any further.
Close inspection and replacement of the head components and careful examination of the integrity of the casting (no cracks) is the next step. The answers to the "whys and whats " will come during that time.

There's a possibility that the low compression isn't due only to leaking valves - the piston rings and cylinder bores could be worn too.
If you've got the time and money set aside to tackle a complete engine overhaul (which is a big job and very expensive) then perform a leak down test to see if the rings are leaking.
If not, cross your fingers, pull the head & rebuild it, and reinstall it and hope that fixed the problem sufficiently enough to let the cruiser run for a few more years.

 

[SteveH]

I also go through ALOT of coolant, 1-2 gallons each time I top off oil. No coolant leaks

You might buy a cooling system pressure tester and pump up the system (not beyond 16 psi or so) both cold and hot and look for obvious leaks. You can purchase (and then own) a cooling system pressure tester for less than the cost of a shop doing this once.

If there are never any pools of coolant under the truck, I would be puzzled as to where that much coolant is going! Buy a new radiator cap, as sometimes coolant can leak out around the cap and evaporate while driving and not show up as a pool. Do you smell coolant while driving?

 

[Rusto]

Adding that much oil and that much coolant makes me think that they are mixing and burning out the exhaust, but I would expect to see white smoke and/or a sweet smell out of the exhaust. Have you tried a wet compression test? If dry compression numbers are lower than wet compression numbers your rings are letting compression leak out of the chamber.

 

[bsang]

Thanks for all the replies.

Regarding coolant, there is never a sign of coolant on the ground. Also, if it leaked from the cap or overflow, even if it evaporated, there would still be residue and evidence of that. My thought was that it was mixing with oil and leaving through the tailpipe. I never notice white/blue smoke out the black, but my 1 yr old exhaust with 5k miles on it does NOT look 1 year old anymore around the tailpipe.

I ended up draining all my engine, trans, TC oils last night, so won't be able to test compression or leak down anymore.

Coolant pressure test requires a running engine right?

Oil cooler - What am I looking for? Repainted it and put new gaskets/seals on it about 2 years ago. Still looks good. .

Is there a way to know the condition of the piston rings and cylinders without another compression test or leak down? I read that if the compression builds quickly on the gauge during a compression test that rings and gasket should be strong.

I'm leaning towards pulling the head, but want to know that the cylinders/rings are good before putting it all back together just to experience the same thing due to bad rings, etc.

I suppose I could refill fluids, but don't want to throw away money if i don't have to.

 

[Seth S]

Thanks for all the replies.

Regarding coolant, there is never a sign of coolant on the ground. Also, if it leaked from the cap or overflow, even if it evaporated, there would still be residue and evidence of that. My thought was that it was mixing with oil and leaving through the tailpipe. I never notice white/blue smoke out the black, but my 1 yr old exhaust with 5k miles on it does NOT look 1 year old anymore around the tailpipe.

I ended up draining all my engine, trans, TC oils last night, so won't be able to test compression or leak down anymore.

Coolant pressure test requires a running engine right?

Oil cooler - What am I looking for? Repainted it and put new gaskets/seals on it about 2 years ago. Still looks good. .

Is there a way to know the condition of the piston rings and cylinders without another compression test or leak down? I read that if the compression builds quickly on the gauge during a compression test that rings and gasket should be strong.

I'm leaning towards pulling the head, but want to know that the cylinders/rings are good before putting it all back together just to experience the same thing due to bad rings, etc.

I suppose I could refill fluids, but don't want to throw away money if i don't have to.

you can pressure test the coolant system without the engine running....it just has to be full of coolant

 

[bsang]

Good to know. I'll do that!

 

[bsang]

Got some updates:

Pulled the head. Pistons and cylinders were clean, but coolant passage ways were all milky brown. Head gasket was not blown, but looks old. The head bolts were quite inconsistent, with most of the left sides (cold side) looking good, and the right sides (hot side) looked gunked up.

Valve cover is super clean.

I did do a coolant system pressure test prior to pulling the head and found a couple small leaks, but don't think it explains the coolants loss.

What are your guys thoughts?

I also got the results from Blackstone on the oil analysis. Overall a good report. Low Iron, high on sodium which could be coolant, but they suspect an oil additive is more likely. Silicon shows possible dirt getting in, but had a new air and oil filter. 3% fuel is high- thoughts here?

 

[pithicus]

Hopefully it's in the oil cooler or the head gasket and not a crack in the oil gallery in the head. I had a 3f that had had a crack in the gallery and it used to do similar things to yours. Sorry don't want to spook you. Definitely pressure test the oil cooler.

 

[partytime]

while its off take your head to a shop and get it magnafluxed to check for cracks