zero compression in cyl 4????

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mike86supra

New Member
Nov 26, 2008
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Sup guys, I just ran a cylinder compression test on my 1990 7mgte and here are my results..

1- 170psi
2- 160psi
3- 160psi
4- 0psi
5- 200psi
6- 175psi

I'm guessing a valve in cylinder 4 is messed up. Most likely stuck open? Or I have no piston rings left. While the car was running, around the back end of the head, a little oil was leaking from where the exhaust gasket is. Forming a little puddle on the exhaust manifold. Correct me if I'm wrong. But the head definitely has to get pulled. And is 200psi in the cylinder next over, a little too much??

I thank you guys in advance for all your help!
 
suprarx7nut

suprarx7nut

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Nov 10, 2006
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mike86supra;1787903 said:
Sup guys, I just ran a cylinder compression test on my 1990 7mgte and here are my results..

1- 170psi
2- 160psi
3- 160psi
4- 0psi
5- 200psi
6- 175psi

I'm guessing a valve in cylinder 4 is messed up. Most likely stuck open? Or I have no piston rings left. While the car was running, around the back end of the head, a little oil was leaking from where the exhaust gasket is. Forming a little puddle on the exhaust manifold. Correct me if I'm wrong. But the head definitely has to get pulled. And is 200psi in the cylinder next over, a little too much??

I thank you guys in advance for all your help!
Click to expand...

0 would indicate a valve to me. I've never seen or heard of bad rings resulting in 0 compression. When I had a stuck valve, that's the only time I've ever seen 0.

Sent from my ADR6400L using Tapatalk
 
Supracentral

Supracentral

Active Member
Mar 30, 2005
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I've seen 0 with a cracked piston, something like this will do it (from recent post by a member):

p1787931_1.jpg


Melted piston will do it too (Friends 2JZ in his MKIV -- serious lean out at high boost on a long high speed highway run) :

will.meltdown.1.jpg


But generally you're going to know about both of those long before you whip out the compression tester...
 
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mike86supra

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Nov 26, 2008
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Thats crazy! Well I only got the car about a month ago, in not running condition. Got it running yesterday, noticed the oil leak, and the car was running very poorly. And yeah I was just throwing things out there lol.. now that I think of it, no way bad rings will give me exactly 0.

I'm going to tear the car down during the week to see the damage
 
suprarx7nut

suprarx7nut

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Nov 10, 2006
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mike86supra;1787948 said:
Thats crazy! Well I only got the car about a month ago, in not running condition. Got it running yesterday, noticed the oil leak, and the car was running very poorly. And yeah I was just throwing things out there lol.. now that I think of it, no way bad rings will give me exactly 0.

I'm going to tear the car down during the week to see the damage
Click to expand...

If you've got a valve issue, make sure the head isn't completely soft. My bad valve seat was the first sign my head was trashed. If you can get it hardness tested, do it.

Sent from my ADR6400L using Tapatalk
 
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mike86supra

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I'm only throwing this out there, but would it be possible to use a 7mge head on the gte block??? I have a seized GE head sitting in my garage. I thought about switching heads on my other 88 turbo engine, but its outside in the freezing cold. That's the only reason why I'm bringing this up. I'm taking off the head off the car with 0 compression in cyl 4. I think it would be more cost effective if I go that route. Should there be anything else that I need to look for when I inspect the head???
 
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mike86supra

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Nov 26, 2008
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WOW! That's crazy.. Snap On's prices are ridiculous. I have to buy a torque wrnech from them really soon, because my autozone one is shot haha. Like they say you get what you pay for.

Thanks for the links
 
Raven97990

Raven97990

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When I bought my set of torque wrenches it was when the tech wrench first came out. If I remember is was $1100 for a 1/4, 3/8 and 1/2. They then came out with one that measured angle in 3/8 and 1/2 so I got those for $1400. I have a snap on xxl box that was $14,000. I will admit I spend the money because I want it to say snapon. I wont own any other box.

But I also had my tools at work and bought a $20 tool set and pulled the head on my wife's supra, so you make the tool, the tool just can make it easier.

Sent from my X10i using Tapatalk
 
suprarx7nut

suprarx7nut

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Raven97990;1789746 said:
http://www.ebay.com/itm/Inspection-...Television_Test_Equipment&hash=item48436860a5

Jeremy had that for the shop before I got a $900 rig from Snap On

http://www.ebay.com/itm/Mini-USB-Wa...348?pt=LH_DefaultDomain_0&hash=item415f9b5fbc

Cheaper laptop driven item-

Good luck!
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WOw, that is crazy cheap! The borescope I use at work is just under $50,000 and looks similar to that first scope. A borescope could have saved me many, many hours and many $$$ on the motor that is in my Black car...
 
Supracentral

Supracentral

Active Member
Mar 30, 2005
10,542
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mike86supra;1789950 said:
Snap On's prices are ridiculous.
Click to expand...

When you're spinning wrenches for a living, or racing cars, and a cheap one breaks and it costs you $100+ in downtime, blowing a deadline on a customers car, or you lose a race because of it, you tend to reevaluate that... :D
 
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mike86supra

New Member
Nov 26, 2008
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Whoaa.. yeah might not be a bad idea to get me one of those. Well I almost have the head off the block anyways. Damn work is cutting into all the time that I'd like to spend working on my car. Anyways I found oil seeping thru the exhaust manifold, and some oil in the bottom half of the intake. I should definitely have the head off tomorrow, with some pictures for you guys
 
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mike86supra

New Member
Nov 26, 2008
127
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connecticut
Head is still in the car. It has some special ARP head studs. They could be standard, I've just never seen them before. What special tool do I need to remove them? And what size? It looks like a torx bolt, so I'd need a torx socket I'm guessing? I just don't want to buy anything and have it be the wrong thing. Thanks for your help so far
 
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mike86supra

New Member
Nov 26, 2008
127
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I'm shooting to take the head off while the motor it in the car. Oh and the studs have a little hex on top. Would I have to remove all the studs once i get the bolts off to get the head out?
 
mecevans

mecevans

Supramania Contributor
Jan 18, 2009
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mike86supra;1792990 said:
Head is still in the car. It has some special ARP head studs. They could be standard, I've just never seen them before. What special tool do I need to remove them? And what size? It looks like a torx bolt, so I'd need a torx socket I'm guessing? I just don't want to buy anything and have it be the wrong thing. Thanks for your help so far
Click to expand...


Its a 12-point 14 mm socket. Make sure you loosen them in the correct sequence and in multiple passes. Then remove the stud and washers.
 
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