calderp

I just got this sweet truck from a friend of mine:













'75 Hilux with a 20R. It runs great except it's going through a ton of oil, 1/2-3/4 qt per tank of gas driving around town since I got it, which is maybe 5 tanks. I'm trying to figure out where all that oil is going.

My friend had it for maybe 6 years, bout a year and a half ago he did the bottom end -bearings, crankshaft, rings, seals. It sat for a few months before I got it and he said it was burning some oil when he drove it but not as much. When he did the bottom end he saw oil inside the intake opening on valve no 4 but he was in a hurry to get back on the road so he didn't replace the seal. Also, there's a tapping noise coming from one of the valves. He says it's been like that a long time. So it's leaking at least some oil through one (or more) of the valve seals.

It's not smoking much, a bit at startup maybe but I'm surprised cause I would think if it's burning that much oil it would be smoking more. I'm not seeing any oil on the ground either.

The PCV valve grommet is the wrong size and it's just sort of jammed in there:



When I pulled it today there was oil in the valve and the grommet but it hasn't been coming out onto the head. The valve rattles when I shake it.
SO probably some oil going through there.
One of the valves is tapping too.

I just did a leakdown and compression test. Compression was 195 on 1,2,3 and 180 on #4. Turned over maybe 8 times with all the spark plugs out to get up to compression. I thought that was good, but I guess high is not always good. Should be 160.

The leakdown, with all plugs out, at 120psi shop pressure at my friend's shop. He just bought the tester so we were new to it.
#1 - 17% - hissing at dipstick
#2 - 8% - slight dipstick hiss
#3 - 7% - slight dipstick
#4 - 25% - hissing at dipstick and carb. Tested this one twice.
On the hose which goes into the fitting which screws into the spark plug sockets was hard to tighten. The hose was floppy and there's no space to get pliers in, especially on #4 which read the worst. The pressure would hit 90psi or so then you could hear it pop up an edge of the o-ring and blow out the spark plug hole a little too. I don't know how much that throws off the percentages, but say it's 5% or less then what does 20-25% on one cylinder tell me? Doesn't sound too bad?

A guy at a motor shop wanted to start taking everything apart and measuring it, of course.

I'm getting a new PCV valve and grommet, then I was planning to pull the head and see what it looks like from there. Might pay the shop to look it over and then hope that all I have to do is lap a couple valves and other small stuff. Seem like the logical next step? Does the compression and leakdown test tell me how important is it to do this soon vs. later? If I replace the PCV, give it some of that seal-softening stuff and just keep feeding it oil for a while am I shooting myself in the foot?

Also, can anyone tell me how to get a good seal on the hose for a leakdown tester? It can't be that hard, right?

ConSeann3ry

If it is hissing at the carb that means your intake valve is leaking. I have never had problems with the hose, make sure your o-ring is good and it shouldn't leak. I just put the base with a socket then just finger tight with the other part. What oil are you running in it? Try a little thicker, or some lucas oil treatment. Might thicken it up enough to slow down your oil consumption.

83

I agree that if you're losing that much oil, it should be pouring out the tailpipe in plumes. My head is starting to burn some oil, and I get big plumes of smoke sometimes. I don't go through more than a quart between oil changes.

I would also try cleaning the engine off a bit (if it's covered with oil) and see if you can find a leak. That much oil ought to be noticeable...whether it's being burnt or dripped.

83

Some hoses are messed up on that thing, too...but I don't know quite enough about vacuum to know if, even though they're in the "wrong" place, if it's still an ok place.

Typically the PCV would go to the fitting that your breather towards the front of valve cover is going to. The breather on the front would connect to the carb, or just have a filter on it. I can't quite tell where the PCV is going, but seems to wrap around and connect to the intake under the front of the carb. I think, so long as it's getting vacuum from the intake, it's ok. But I'm not positive.

There's a lot of rigged stuff on that truck, which is fine, as long as it's rigged "right". But I'd be wary. There's some funky electrical stuff going on, too.

gillesdetrail

iTrader: (1)

On the compression numbers, the actual number can be misleading, the variation between numbers is also important. I've had a lot of fluctuations between different testers on the actual numbers. And generally, oil consumption coming from bad valve seals or guides would be more apparent at start-up, because the hot oil slowly drips in the combustion chamber when the engine is turned off, then it is burnt at start-up and causes fumes for a short while. It would have to be one lose head for it to cause all your consumption.

I'm thinking if he was in a hury on the rebuild maybe he cut some corners on the ring gap, piston to wall clearance and machining (hand hone maybe?) And like 83 said, the previous owner seemed like a ''that will do'' type of guy

ConSeann3ry

Yeah, that bottom end is suspect, did it get machined? new pistons, etc. Or did he just re-ring it and throw some new bearings in? Probably didn't get it honed right and the rings didn't seat, or maybe he did but if it's old pistons there's only so much you can do. 120 psi is also a lot for a leak down test. I think I used 15 psi last I did one. Wonder what the gauge would say at that.

You try adjusting the valves to see if that fixes your valve leak on 4?

skypilot

iTrader: (1)

These trucks are so tough, I bet its just leaking out. I would not bother doing just the head, it tired.

jimbyjimb

iTrader: (1)

What does being tough have to do with a potentially crappy bottom-end rebuild?

Oil cannot magically disappear. If it's not leaking it's burning. There are many things that can cause oil burning, but as has been mentioned, I suspect it was poor assembly of the bottom end. That is an insane amount of oil burn and I would think it would smoke like crazy. If it's leaking that much, you'd notice.

Check your spark plugs for black soot or deposits. Confirm the oil is burning, go from there.

I have a feeling your friend doesn't have a whole lot of experience rebuilding engines, which is fine. Everybody has to learn sometime.

Could just be the head as well. These engines pump a lot of oil upstairs and bad valve seals can leak a lot. Could be a combo of rings and valves too. I'd find out how much experience your friend has on rebuilding engines because improperly installed rings can leak a lot of oil into a combustion chamber without hurting the compression. That is a lot of oil, lol.

calderp

Oh hell ya, that's some very useful advice. I wasn't getting many replies at first so I haven't checked this in a while. Here's where I'm at:
As far as I can tell the engine wasn't leaking oil, as in I wasn't seeing any drips when I parked and I figure even if it's only leaking at pressure with the kind of oil I'm going through some of it would have to end up on the ground.
Anyway, I pulled the head. I'm getting it hot tanked and checked at an engine shop, then I'm going to replace the valve seals.

Looks like ya'll were right about the bottom end. I see light scuffing on the cylinder walls and with the pistons just below the wear lip I've got between 1/32" and 1/16" of play between the piston and the cylinder wall. I think the rings would account for some of this? But that seems like waay too much? I've never opened up an engine before so just going by feel. It also looks like the pistons might be switched around? The one in cylinder 1 (towards the front of the truck) is marked 4 and vice versa...

I'll post more with photos soon, going to go and try to pull the block today so I can go get it mic'ed. Hopefully I'll know more this afternoon.

Couple questions for now:

I already took the radiator out. I am going to be able to slide the engine forward enough to pull it without pulling the transmission or do they both have to come out?

All the pistons are marked with a "2". Does that mean that this is a 2nd set of oversize pistons (ie. engine has already been bored)? If so, can I bore it again if I have to, or am I going to be looking at a new block?***

Should I replace the valve springs? They're probably original, but I haven't seen any signs of valve float. They're cheap, $25 for a new set, not sure what the shop would charge to test em, but sometimes I'm inclined to keep the old ˟˟˟˟ until it breaks just cause I don't trust the parts that get manufactured now...

calderp

Oh and should I order an oil pan gasket? The ones on rockauto are cork. But I think I remember reading on here somewhere that maybe there's some on a roll type gasket material that's better than the cork?

jimbyjimb

iTrader: (1)

Is there much of a ridge at the top of the cylinder?


Sounds like you need to do a bottom end rebuild. Scoring on the walls is bad juju. trying to run it that way is pointless.


Yes, replace your valve springs.


I'm very sorry this has turned out this way for you. Consider yourself lucky though, many have it much worse. R's are very simple to assemble but cutting corners has a high price. It's not overly expensive to do it right.


The trans does not have to come out. Put a jack or stand under the bellhousing/trans body and unbolt it. Make sure you clear the input shaft from the flywheel and the R will just come right on out, piece of cake.


You'll get a new pan gasket with your rebuild kit.

83

Take off the hood, and you can lift the engine straight out. Doesn't hurt to have pulled the radiator, since then there's no chance of banging the engine into it.

Do the clutch while it's apart.

The oil pan gaskets for these trucks are cork. They don't seal well, but they are what they are, so...later model trucks (I think starting in the mid-late 80s) have a slightly different oil pan which doesn't have the little ridge on the mating surface that ours does.

So the later ones are actually meant to used FIPG (form in place gasket from Toyota) or RTV sealant. There are people (including myself) who used that gasket maker instead of cork. If you're very careful to put it on correctly (there's a method you can find in the FSM (factory service manual) which shows the right way to put the sealant), it shouldn't leak. Or at least, it should leak less than the cork gasket will.

For a while I was trying to find a later model oil pan for my truck so I could get rid of that ridge, but then I moved on to other things...

gillesdetrail

iTrader: (1)

I have a cork gasket that I sprayed with some kind of liquid spray gasket and it has been leak free for almost a year, mine is a 81 22r