So I had a recent spark plug blow out on cylinder 1 and i've read that its a pretty common issue amoungst cobalts. well its been two almost 3 months later and I was driving not pushing the car just cruising and the 'balt started bogging....I thought another blow out occured, but instead there is just a small pool of oil UNDER the spark plug...(not in the coil not on top of the spark plug but under it.)

I know that if the oil is above/covering the spark plug it is usually just a valve cover gasket and possibly the o rings for the spark plugs, but my issue makes me think that it may be a head gasket or related issue... or maybe a valve seal...?

Any thoughts or comments to help would be appreciated!!

Thanks

 

typically the only thing that will cause you to see oil on your plug is a piston ring, piston, or a possible valve seal. When the plug blew out did any of the electrode or metal pieces fall into the cylinder wall?. I have also fixed many of these by using a helicoil kit. If the person didnt clean the cylinder chamber out good from the shavings after the repair this could cause an issue too.

 

The electrode was not found after the repair....this sounds like it is going to be an expensive repair

 

well what you need to start with would be a compression test first, then a leak down test if a compression test looks good that will find your problem

 

I will try the compression test...can you explain a leak down test?

I had a buddy look at this and he was suggesting it might be a valve seal leak...

 

typically a leak down test will show better results when finding valve stem seal issues etc. With a leakdown test it pressurizes the cylinder and valves with air. If you hear air coming out the intake manifold, you know its an intake valve issue. out the exhaust mani, and exhaust valve. through the crank case weather it be the pcv valve, (vent in our case) a piston or ring issue. unfortunately if you dont know the proper way to do one you can get false readings. start with a comp test go from there

 

thanks man appreciate your fast and helpful response!

 

no problem man good luck.

 

so compression test results were:

Cylinder #1 - 120psi
Cylinder #2 - 210psi
Cylinder #3 - 180psi
Cylinder #4 - 180psi

Alldata states that the psi should be 100, which makes me conclude that there is carbon build up in every cylinder.

Leakdown test results were: air was coming out of the intake, which leads me to believe that the intake valve is done, bend, shot., I dropped the car off at my local and trusted mechanic. Now I wait for the dreaded call.

I just don't know how I could have a bad intake valve. The car has 130k miles on it. I hardly push it. (I use to run with it more often when I was younger and right after I had all the mods done. Now I just cruise.

The issue happened while I had cruise control on at 50mph. The car started going up hill and then the CEL started flashing and the oil started gathering.

Head work here I come...

 

same thing happened to me a few months ago...it ended up being the oil control rings..

 

I've never heard of an Oil Control Ring what is that?

 

Broken piston on #1.

 

Lowest ring on the piston. Top is called a flame control or simply compression ring #1, the middle is the compression ring or compression #2, the 3rd ring is a multi-part ring composed of two thin oil scraper rings and one spreader that goes between them to keep them in place. A cracked piston that breaks around the third ring land will result in a failure of the oil control ring and allow a ton of oil into the cyl. Main reason is damage to the cyl wall though, which allows compression past and oil past.

 

Ah...so I have heard of that then just didn't know that's what it was called. If it is letting a ton of oil into the cylinder then shouldn't the car be smoking? Unless that cylinder isn't firing in which case that should be very evident. If the car isn't smoking then could it be the valve seal letting oil past?

 

My car isn't smoking but you can smell it burning oil. I thought for awhile that it was the valve seals or at least hoped that's what it was lol...

ItalianJoe1...I can only pray its not a broken piston and i'm more then positive its not. The car runs fine and there is no banging or clanking.

Tjolley...sorry to hear your troubles..how much did all the work set you back $$ wise?

 

Its all good it grooved a cylinder so I bought the sleeve puller and dropped 4 new sleeves in and did all forged imternals...all I had to do was buy parts I did everything myself and the machine work also. I bought the fully coated forged pistons from over the top performance.. Zz performance rods. All new bearings head gasket new valves... I could add up the total in let you know... if you wanna pm me your phone number I could text you some pictures of my rebuild..

 

alldata is incorrect on cylinder pressure it should be 190 to 210 as for your leakdown if the piston wasent on tdc compression the test was a failure and as for a bent valve i doubt it valves can wear and leak its just the nature of the beast

the top ring does 90% of the work the second ring will pickup the remaining the 10% but it is more of an secondary oil scraper

 

read this

Piston Ring Tech - The Latest Developments In Cylinder Sealing - Hot Rod Magazine

 

Valve seals will not lower compression, as they are outside the chamber. They will cause oil burning, and usually a cloud on startup as the cyl will fill with oil that was sitting on the valve.

 

My car ran fine and made no strange noises with a broken piston, I drove it for 3 months like that, other than the compression being 140 on that cyl and the slight subaru sound to the exhaust and oil on the plug, car seemed normal.

I'd bet thats what you have here. Not an uncommon problem on these cars.

 

between my job and my fiance I barely have every other weekend to myself, which means I wouldn't be done with a rebuild (myself) for a few months haha... not to mention I don't have the uttmost confidence to pull the head off my cobalt.

i've already dropped my car off at a shop and i'm just waiting for the inevitable phone call now. I do appreciate your help though..

 

I had a feeling alldata was wrong being that all the cylinders had high readings..unless like I stated that they have carbon build up..when I did my leak down test the cylinder #1 piston was at TDC...I made sure of that

 

well I will keep this thread posted on the results...i had to make this thread as I couldn't find any other that was a similar senario...

Just like everyone else I want to share my experience and help others if I can

 

Normal compression on these cars is in the 190-200 range. So you definately have a low reading on #1. Usually a valve will show up worse than that, and these cars don't really burn valves, it's especially hard to do with sodium filled exhaust valves anyway.

 

yeah i figured all data was off with 100psi...thanks for the input