Whats the best way to see if the motors healthy

[prokeep15]

I was wondering whats the best way to see if everything in my motors healthy and ready for doing some sprints down the track this season. Its been sitting for the past couple months and never had a rebuild, and when it went into hibernation the motor seemed sound, minus the tranny which is in the rebuild process. So I have a scan tool, compression tester, any good ways to going about and checking everythings ready to run? Also is it necessary to open the motor up to check everything out?

 

[onefastcar]

might be a good or bad idea opening the motor, how many miles and what does you're oil look like when changed, is this a car you just purchased or have had since 82-87 whatever year it might be i would use a little good judjement on you're part, unless you do not mind a rebuild. From what i have seen people thrash these cars pretty good with even 150k on them you just need to assess your situation and if a rebuild is a no bigee then go for it.

 

[Bonden]

Once you have it running again, a vacuum gauge will tell you all sorts of things about an engine's health.

HTH

 

[Hot Air]

My thoughts...others will have theirs.

First...check the compression to see if valves and rings are sealing.

Second...drop the oil pan and clean off the oil pickup screen. You'll be amazed at what you find there!

Third....replace timing chain and sprockets if motor has more than 50,000 miles.

Fourth...what is oil pressure?

Conrad

 

[prokeep15]

The car has 60k miles, oil always changed every 1k miles, I'm the third owner but I know both the pervious owner and original owner(both own GN's) and good friends with them. How do I go about doing a vaccum test i've always been interested in that? Also what should my compression test look like? Also my oil pressure has always been pretty consistent since i got the car at 35k, what should that look like also?

 

[85HOT-T]

I feel a pressure leak test is the best way. It give way more info than just a compression test. Though u have to have a leak guage which cost a little more than a comression guage, just a little, lol.

 

[Hot Air]

I would do the compression test first. Then do the leak-down if all is ok. Purchase a compression tester from the local parts truck such as Snap-On or ???. Won't be cheap but good tools are an investment. You will want one that will hold the reading. Check one cylinder at a time and reset the gauge back to zero. I pulled all the injector wires off the injectors (don't want raw fuel in cylinders) and pulled the spark plugs out (so motor could turn over easily). You are looking for compression that is consistent from one cylinder to another. Should be plus or minus 10-15% or so. Do the test and post your results. Everyone will tell you if it is ok.
Conrad

 

[Blown&Injected]

Agree with leak down test but I would relieve fuel pressure and just disconnect the orange wire at the connector just several inches down the positive cable from the battery - easier than pulling all the injector wires.

Engine should be warm when doing comperssion test.

 

[prokeep15]

So when doing compression no fuel and no plugs in?

 

[Blown&Injected]

Yep, and hold the throttle body wide open
if the compression is low a squirt of oil in the cylinder may increase the compression and that indicates rings.

 

[Louie L.]

Just my .02
A compression test can be decieving. A leak down test is the correct way to check for ring and valve seal.

 

[85HOT-T]

If u do a compression test, make it easy on urself and pull the fuse for the injectors, or disconect at the pump( you know the harness), start the engine, might start and will die in like a sec, you will have no fuel at all running into the injectors then. Fuel is very bad, it will wash all the oil off the cylender walls, and give u lower compression.

Yes leakdown is the best way though

 

[prokeep15]

How is a leakdown test done and what does it require, a step by step would be cool i'm sure my neighbor who works as a mechanic at the local pontiac dealership can/does get the tools.

 

[VadersV6]

I got 150psi on all the cylinders, yet the motor spits out ALOT of blowby. I fill up about 1/2 pint of oil every 5 days or so in my catch can. Before the catch can, the smoke coming out of the breathers was killing me. I'd get to work high as a kite, my eyes glazed over and I couldnt breathe. So yes, a compression test is a good first start, but will not be a good test of the condition of the oil rings. My car sat for 4 years, and Im sure they didnt spray penetrant in the cylinders before firing it back up. Hell, the spark plugs were all cracked, and had been cracked for so long that the inner core had rusted, and the rust had seeped out through the cracks. There was really no care taken when firing the thing back up. So the rings were probably damaged a little bit from rapidly breaking the bond the rings had with the cylinder walls. I would recommend pulling the plugs and spraying penetrant in all the cylinders, and try to have the pistons down in the hole far enough that the oil spray can reach the rings all the way around.
So once the motor is warmed up, pull the hose to the PCV and plug it so you have no vacuum leaks. If you have breathers, pull the one out on the drivers side and look to see how much blow-by you have.
Then do a basic tune up. Plugs, wires, etc. Then adjust IAC and TPS. Warm it up and take scanmaster readings and post them here.
Oh yeah...I get 18 inches of vacuum at idle, yet there still is alot of blow-by. When I first got it, I had 12 inches and it barely idled at all. That was an acuumulation of cracked injector o-rings, bad hoses, leaky EGR, etc. So even a vacuum test doesnt tell you everything.

 

[85HOT-T]

How is a leakdown test done and what does it require, a step by step would be cool i'm sure my neighbor who works as a mechanic at the local pontiac dealership can/does get the tools.

Well u need an aircompressor and a leakdown guage. It almost looks like something for a/c. Get the piston at bottom or top ( been a long time since I did one) center on the power stroke(so both valves are closed). Put the guage into the spark plug hole and set it to the recomended psi, probably around 80. One guage tells you what the psi that the pump is putting into the cylender and the other is the leakage percent.

Now when u do this take your radiator cap off, turbo off and up pipe off. This is so you can hear where the air is leaking. Out of the exhuast, Obviously exhaust valves, Intake, Intake valves, radiator head gaskets. Oh and pull your oil dipstick, so yo can hear if your rings are leaking. This is basicly it. This will tell you how much air you are loosing, and where it is going.

You will need a good sized air compressor so its not going on every 2 minuits so you can listen. You may have to listen carefully too.

I thik I have everything, if I am missing anything anyone just correct me, like I said it's been a while, and I'm sure there are people here who have done it more than I have too.

Hope this helps out.

 

[prokeep15]

alright the results are in and on the compression test i got 120 across the motor? little low?Or how'd I fare? Sound decent enough to go fast again?

 

[85HOT-T]

All the same? If they are the same you are in good shape.