DIY Engine rebuilding logistics!

Technical Discussions - Got a mechanical problem?

Moderator: bajabob

Post Reply
Scoobytruck Contributer
Posts: 46
Joined: Fri Aug 18, 2017 7:35 am
Location: South East PA

DIY Engine rebuilding logistics!

Post by SoobyToo58 »

I'll try and keep this short and to the point but that's not my forte.
I'm looking to possibly buying a used engine to rebuild myself for my Baja Sport!
Finances are a major concern and I have no problem getting down and dirty of I have to.

My mechanical experience!
I've never completely rebuilt an engine before but in my younger days (late 1970s) I've done some partial major tear down and rebuild work on American engines like GM small blocks and such. Rebuilding heads with valve trains and cams and such. I've also done semi major engine work on my own vehicles here and there through the years and everything I've attempted has always turned out well.
With my Baja I've replaced leaking valve cover gaskets, an oil pan and the timing belt along with all the pulleys and tensioners and the water pump that went along with it. I've also done other knuckle busting odds and ends. My only screw up was over torquing and breaking off a valve cover bolt in the head when doing the valve cover gaskets. Part of the bolt was left in the head and not removed. The rest of the bolts went on well and the valve cover gaskets haven't leaked in the 2 years since it was done despite the broken bolt being left in the head.
The bolt I broke off was the first one I tried reinstalling so I figure it was my inexperience working on an aluminum block engine along with having lost a feel for a torque wrench and/or an incorrectly spec'ed bolt.

Currently the engine has a slow oil leak which I can't quite pinpoint despite trying many times to locate the source. It's coming from somewhere on the lower rear portion of the engine on the right side but that's as close as I can get to finding it.
It also seems to me that the engine oil turns dark and dirty quicker than I expect it should but I'm not sure if that's my imagination and that's normal or if it has to do with the oil leak.
I bought the vehicle in 2017 and it came with all the repair records in detail. The previous owner was very fastidious with that.
The head gaskets were replaced not all that long before I bought the vehicle but I can't tell if the right side head gasket is the source of the leak or not. There is no coolant leakage outside or inside the engine!
Despite the engine running well (it has 126,000 miles on it) I'm concerned about that oil leak for the long term and wondering what might happen over time with it.
I'm toying with the idea of getting a used engine and rebuilding it in my spare time to have it available immediately if and when I run into a major problem with the current engine.

What I need!
To start off, I'd like some input from any of you guys who might have something to say regarding what might be going on with my current engine.

1) What are some of the more likely possibilities about what the oil leak is all about? Should I be very concerned or not so much?
2) Should I be more immediately concerned, more concerned in the long term or not concerned at all about the leak?
3) Is it a sign that the engine is on its way out or just a messy annoyance?

Having worked on my own in the past on older American V-8 engines, sometimes a slow persistant oil leak was more of a nuisnace than a mechanical concern and was something that you could live with as long as you didn't piss off your father too much with oil stains on his driveway or in his garage! Also, in some ways, those older engines could put up with more youthful abuse and neglect than modern, smaller Japanese engines... or at least it seams that way to me.
That tells you kind of what my mind set is with the oil leak. I'm not sure what my concerns should be and I want to get a handle on it. I hate being unsure with all this nonsense and not having a better feel for what's going on.

So... let's just stick with that to begin with before I get into possible engine rebuilding and all that!
Scoobytruck Master
Posts: 198
Joined: Sun Apr 15, 2018 4:38 pm

Re: DIY Engine rebuilding logistics!

Post by ZUBAJA »

First: when you get a chance, have your engine running and take the oil fill cap off. Observe and see if you have blow-by (vapors / "smoke") comin out of the oil fill.
Next: check your PCV valve (unless you are one of the rare ones who have replaced it). It's on the passenger side near the intake manifold. A plugged PCV and blow-by are a common cause of oil leaks. These are the optimistic possibilities
Right rear leak on the engine could be what they call the "Oil separator" (???). This is kind of a crescent shaped cover on the back side of the block (behind the flywheel - not easy to get to). I don't know what year they "upgraded'' them, but the early ones (my 1998) had a plastic cover. The replacement was metal. The cover (IIRC) was for access to the right rear piston wrist pin (more about that later)
Of course, there's always the possibility of a rear main seal leaking (always replace the rear main and oil separator cover together)
"Rebuild" (overhaul, re-ring, or whatever you want to call it): You'll want a source for QUALITY parts (avoid the ebay bargain stuff). For head gaskets, I used the special ones from the place in Oregon (never can remember the name of that place, want to say it was blue diamond or something like that. Pricey, but REAL good stuff. I believe I used them for the '98 DOHC, and I used Subaru OEM for the SOHC in the 2006 Forester.
You'll want an engine stand (cheap from H/F is fine)
I always like to used a piece of cardboard and draw a rough outline of whatever I'm working on (say bellhousing or timing cover) and I poke a small hole and place each bolt removed in the respective place on my template.
There seems to be a lot of banter back and forth about if the head bolts are reusable or not. After reading several threads where folks were reusing head bolts on COMPETETION engines, I tried it and had no problem. I do advise getting a tap and cleaning the threads in the block before reassembly.
You remove the heads, then there are access places to remove the piston pins (you may, or may not have to clean any ridge wear from the cylinders - I didn't other than carbon buildup). After removing the access plugs (BIG Allen screw plug), you remove th ewrist pin retainer clips (IIRC snap ring?) and you will have to fabricate or get the special puller to pull the wrist pins. They are full floating wrist pins and there may also be some crankcase funk making it a little difficult to pull them out. After removing each respective pin, you rotate the crank to push the piston to the top of it's cylinder. I don't remember exactly what I used, but you have to have some kind of spacer to replicate the wrist pin being in there.
On my 2006, I found all the rings to be within specs for end gap even after 200K miles. I checked them, cleaned all carbon from the rings and grooves,
Ran a dingleberry hone through each cylinder and was good to go (the teardown was because of a cracked head). I didn't bother with the bottom end. There are plenty of videos and tutorials out there. This kind of gives you an idea of what you are looking at. Dennis
P.S. My Baja is right at 210K and it runs fine. Have a '02 Forester that is pushing 240K and our "low mileage" with only 120K
Post Reply