Diaries of the Noob Mechanic: Fuzzydunlop's '85 MR2

[manimal]

Sucks that the engine is going fuz.


Once in a while I used to drive our 2002 avalon and think, wow if you dropped one of these v6s into a 2000 lb car it would go like stink!

 

[JCH13]

I'd vote supercharged engine, or get higher compression pistons for the engine you already have.

I'll be rebuilding a BP8 engine over the winter, so you won't be alone!

 

[slag]

You might be getting ahead of yourself. Both cylinders 3 and 4 were low, with 3 being the lowest. I'd take the head off first and do a visual inspection. Might be a bad gasket or cracked head or something like that. Stranger things have happened.

 

[JCH13]

You might be getting ahead of yourself. Both cylinders 3 and 4 were low, with 3 being the lowest. I'd take the head off first and do a visual inspection. Might be a bad gasket or cracked head or something like that. Stranger things have happened.

I was under the impression that if compression improved significantly with the addition of oil (what I assume fuzzy did for the 'wet test') that it was the piston rings leaking. Am I missing something?

 

[slag]

I was under the impression that if compression improved significantly with the addition of oil (what I assume fuzzy did for the 'wet test') that it was the piston rings leaking. Am I missing something?

No, you aren't missing anything, but if it were me, before I went and bought a new engine, I'd take off the head and do a visual inspection.

 

[JCH13]

No, you aren't missing anything, but if it were me, before I went and bought a new engine, I'd take off the head and do a visual inspection.

Oh, definitely. It may just need a re-hone or re-bore and new rings but not a new engine.

 

[Aikouka]

Oh, definitely. It may just need a re-hone or re-bore and new rings but not a new engine.

It seemed like the fact that the engine isn't terribly powerful was making him not want to go through all the trouble of repairing it. I guess I can't blame him there... it may be cheaper to have the engine repaired, but it's a lot more fun to double your horsepower. ()

 

[JCH13]

It seemed like the fact that the engine isn't terribly powerful was making him not want to go through all the trouble of repairing it. I guess I can't blame him there... it may be cheaper to have the engine repaired, but it's a lot more fun to double your horsepower. ()

True story. Which is why I suggested going with the supercharged 4A-GZE MR2 engine, which won't be such a radical engine swap, but will be capable of 200+HP instead of 112HP. Heck, rebuilding his current engine with forged 8:1 compression pistons and adding a SC would be the same thing, no swap needed. Not sure about engine management though...

 

[FuzzyDunlop]

No, you aren't missing anything, but if it were me, before I went and bought a new engine, I'd take off the head and do a visual inspection.

Ok, and how difficult is that? Would I need to be buying a new gasket and other items if I start digging around in there? what all would I need? I haven't been that deep into an engine before. would have to drain coolantt too probably, Wich is a pain in the ass.

 

[FuzzyDunlop]

ok, so I did a backyard leak test.
Took the spark plug hole insert from the compression tester and hooked it up to my air compressor hose.

Then I put cylinder #3 at Top Dead Center.

Screwed in the hose

and let air press in
Immediately I heard air coming out the exhaust.

but I also lifted the dipstick and heard a difference in sound and also felt a small amount of air coming out of the case. Some guys on youtube say it is normal to have a little bit of air coming out of the case.

So at this point, keeping my fingers crossed that its just a bent or burnt exhaust valve. not rings. Cuz valves are easier to change, right? ...right?

 

[RocksteadyDotNet]

LOL @ picture of the exhaust pipe to 'show' the air coming out.

I doubt it's a valve. As you correctly summised, if dropping some oil in brings the comp back up, it's gonna be the rings.

 

[FuzzyDunlop]

LOL @ picture of the exhaust pipe to 'show' the air coming out.

I doubt it's a valve. As you correctly summised, if dropping some oil in brings the comp back up, it's gonna be the rings.

this is true.
There was a lot of air coming out the exhaust though... Im going to redo the test tomorrow to be double darned sure I was TDC.
But even then. as you say. My compression test says rings.

 

[RocksteadyDotNet]

this is true.
There was a lot of air coming out the exhaust though... Im going to redo the test tomorrow to be double darned sure I was TDC.
But even then. as you say. My compression test says rings.

Yeah, I could see from the photo.

:sneaky:

Doing the rings might not be that hard. You should be able to do it without removing the engine or the head.

Just remove the cross member and sump and drop out the crank. Getting the pinstons back in the bottom might be a bit tricky though.

I dunno though, it might be different on an MR2.

 

[JCH13]

It is possible that you need rings AND exhaust valves in cyl 3. Note that every cylinder showed noticeable improvement when oil was added, but that oil didn't bring 3 up to ~180psi like the others. In fact, cyl 4 showed MORE improvement than cyl 3 when oil was added.

Yes, you should feel air (a little bit) coming out of the crank, blow-by is to be expected.
You should not have felt air coming out of the exhaust. If you redo the test, check your intake to see if intake valves are leaking also.

 

[LTC8K6]

this is true.
There was a lot of air coming out the exhaust though... Im going to redo the test tomorrow to be double darned sure I was TDC.
But even then. as you say. My compression test says rings.

On the compression stroke...

 

[FuzzyDunlop]

On the compression stroke...

ya that would make more sense wouldnt it? Ill take the dizzy cap off and see where the Rotor is at. THat'll garantee me seeing exactly which stroke I am on.
I may not be able to do the test today thought. Long day at work ahead.

 

[slag]

On the compression stroke...

Exactly what I came to post. Make sure you are TDC on the compression stroke.

Bottom line, we can conjecture all we want, but until you pull the head and do a visual inspection, you won't know much. Take the hour or so to pull the head. If you are going to put it back together to run, you would need a headgasket. Otherwise, if you were going to work on it, you would need one anyway. If you were going to put another engine in, then no point in buying a headgasket....

 

[BUTCH1]

Ok, and how difficult is that? Would I need to be buying a new gasket and other items if I start digging around in there? what all would I need? I haven't been that deep into an engine before. would have to drain coolantt too probably, Wich is a pain in the ass.

No, the pain in the ass will come when trying to remove exhaust manifold bolts that have been there for 25 years..

 

[FuzzyDunlop]

Well today I learned that Japanese engineers must have very tiny hands!
Getting at some of the bolts on the intake manifold was like playing Snake on my T1-83.
Also getting the crank pully off was a chore and a half.

This is the progress I made towards getting at the headgasket.

I am one step away from pulling off the head but the geniuses over at Toyata circa 1984 decided to put a octagonal 10mm bolt inside the engine, instead of a regular hexagon. the only tool set I have is hexagonal. Would a dodecagonal (12 sided) socket fit over them?

Its tricky, but I hear the key is keeping everthing organized and labeled.

I forgot to order a new intake manifold gasket. Will have to do that on Monday. Oh well, lots of cleaning to do till it gets here.

Noob question of the day: do I HAVE to get the head machined before I put it back on... or can I just cross my fingers, clean it real good, plunk it on and pray?

EDIT: THIS IS FUN!

 

[LTC8K6]

Its tricky, but I hear the key is keeping everthing organized and labeled.

Kitty appears to have everything under control.

 

[FuzzyDunlop]

Kitty appears to have everything under control.

that cat is more like a dog than some dogs. Seriously. He does tricks, and he is content to just chill out with me while I work.

 

[JCH13]

Check the head for flatness, if it's within spec you'll be fine and won't need to deck it. All you need is a decent straightedge and a ruler. You will probably check it in a pattern like this:

Good luck!

 

[FuzzyDunlop]

I got my hands on a 12 point socket set. Turns out I made an error when looking at the head bolts, they are actually twelve pointed and not 8 as I had thought.

Lots of work today. The head is off

Here is the old gasket. It wasn’t in too bad of shape to tell the truth. No obvious points of concern. And that concerns me.

Here is a shot of inside cylinder #3 where I was getting bad compression. No signs of wear on the cylinder wall.

The only difference between cylinder 3 and the rest of the cylinders was that the carbon inside of it was DRY. The other three cylinders were all WET. What could that possibly mean? Heres a photo of cylinder #2 to compare.

The below photo is an example of the carbon build up on the valves. What is most interesting is that the carbon build up on cylinders #1 and #2 was more so than the build up on #3 and #4. Below is a shot of the worst, #2.

Could it be that cylinder 3 was being starved of oil somehow? All the oil feed lines look to be clean and in good shape. The coolant lines were rather clogged, and one of cylinder #3’s coolant passages was completely blocked.
Anybody have input on why C3 would have been dry?
Good news is that the head is flat. All surfaces showed no signs of warp. For now Im just working in getting everything clean, and finding a reason why C3 is dry.

 

[Howard]

What's wrong with the piston dome? It looks like it's shaped differently from the others.

 

[FuzzyDunlop]

What's wrong with the piston dome? It looks like it's shaped differently from the others.

Its the same shape as the others. I think it just looks a little different because the light isnt reflecting off of the piston because it dry.

Here is #4 for comparison as well.
And note that the two photos of cyinders above are with the piston at bottom dead center. the one below is at Top dead center.