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3.5L lost compression in cylinder


mandersen8
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Hi everyone,

 

 

I have posted this in many places but here so I thought maybe I would see what you all have to say about this topic.

 

I have done lots of research on this but want to know if anyone here has any suggestions here.

I have a 02 pathy 5speed manual 4x4. It's the 3.5L V6. 

Now I have low compression in cylinder 1 only. This usually mean the exhaust valve is wide open. I have been running valve cleaner throw it the last month some improvements but service engine light still blinks. So I have two option I know of.
1. Open the engine and have both head removed and replaced what the issue is.
Or 
2. Replace the engine. 

Here is my question.
Does anyone know if there is only options then what is above? Or a great place to get a good engine that has a good warranty? I have to make sure the engine came off a manual as the engine for the manaul do not have a power valve.

 

Please send me clarification question or suggestions.

Thanks,

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Run a leak down test you can actually see what is causing the problem.  

 

I would do headwork to these engines, but step 2ß after you remove the negative battery cable should be to pull the engine.

 

This is an excellent example of a leak down test with a smoke machine.  Before the smoke he couldn't determine the cause of the leak.

Edited by system_f
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So some ATF was thrown down the cylinder and white smoke came out when it was started. 

 

Why would you do headwork over just replacing the engine. Unfortunately I am not a good machinist but I can pull the heads lol. 

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ATF in a cylinder will make it smoke, yes, but that doesn't really tell you anything. The usual test is to check compression dry, then shoot a little oil down the bore, then check compression again, and if your compression gets way better, that suggests your rings are junk (the oil is helping them seal). If the compression's still trash, that points to your valves. A leak-down test pressurizes the cylinder with air (with the valves shut) and seeing where the air escapes. Using a smoke machine instead of just compressed air means you can see where the smoke's escaping instead of just listening for the leak.

 

What to do depends on how excited you are by the prospect of tearing down a VQ and how soon you need it back on the road. If it's urgent and you'd rather not screw around, chuck an engine at it. If you're intrigued and have some time on your hands, open it up. Either you'll find the problem and fix it for less than the replacement would've cost or you'll find that it's properly buggered and have an excuse to chuck an engine at it.

There's some good info here regarding which engines will swap into yours. Good luck!

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10 hours ago, Slartibartfast said:

ATF in a cylinder will make it smoke, yes, but that doesn't really tell you anything. The usual test is to check compression dry, then shoot a little oil down the bore, then check compression again, and if your compression gets way better, that suggests your rings are junk (the oil is helping them seal). If the compression's still trash, that points to your valves. A leak-down test pressurizes the cylinder with air (with the valves shut) and seeing where the air escapes. Using a smoke machine instead of just compressed air means you can see where the smoke's escaping instead of just listening for the leak.

 

What to do depends on how excited you are by the prospect of tearing down a VQ and how soon you need it back on the road. If it's urgent and you'd rather not screw around, chuck an engine at it. If you're intrigued and have some time on your hands, open it up. Either you'll find the problem and fix it for less than the replacement would've cost or you'll find that it's properly buggered and have an excuse to chuck an engine at it.

There's some good info here regarding which engines will swap into yours. Good luck!

Thank you for this. Yeah after throwing ATF the compression went up. If it the rings would it be better to just Chuck a engine in it? I'm just trying to fine the cheapest path. 

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Compression will go up a bit generally when you do the test, but if it goes up like crazy then yeah, not great news for the rings. You'd have to tear it down pretty far to do rings, plus possible machine work if it turns out the bore is chewed up. I don't know what a VQ goes for but replacement would be less screwing around for sure.

Make sure the motor you're putting in is better than what's coming out! When my dad looked for an engine for his '03, he couldn't find one locally with good compression numbers.

One last idea... I've heard of guys freeing up stuck rings by pouring seafoam or marvel mystery oil down the plug holes and letting it soak. If the rings in #1 are just stuck in their slots rather than actually damaged, and you can get them loose again, they may go back to sealing up properly. This assumes that the rings are stuck rather than worn out or damaged, but it's a cheap thing to try, especially if the engine's junk otherwise.

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7 hours ago, Slartibartfast said:

Compression will go up a bit generally when you do the test, but if it goes up like crazy then yeah, not great news for the rings. You'd have to tear it down pretty far to do rings, plus possible machine work if it turns out the bore is chewed up. I don't know what a VQ goes for but replacement would be less screwing around for sure.

Make sure the motor you're putting in is better than what's coming out! When my dad looked for an engine for his '03, he couldn't find one locally with good compression numbers.

One last idea... I've heard of guys freeing up stuck rings by pouring seafoam or marvel mystery oil down the plug holes and letting it soak. If the rings in #1 are just stuck in their slots rather than actually damaged, and you can get them loose again, they may go back to sealing up properly. This assumes that the rings are stuck rather than worn out or damaged, but it's a cheap thing to try, especially if the engine's junk otherwise.

I've been throwing seafoam in the gas. Will try putting it in #1. I found a engine here (https://used.remanns.com/quote-details.php)

Any oppion of this would be great. I think it looks good but it could be sh**. I have never used them before

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5 minutes ago, Slartibartfast said:

No idea, sorry. You might try looking up the business to see if other people have posted forum rants about it, and see what their warranty policy is. Also get compression #s if you can.

Will do that. At least I did a bit nothing bad as of now.

 

I got compression # it was 40psi at first, then after the ATF was thrown down the cylinder it jumped to 90psi.

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