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Head with leaky valves advice needed #5007135 02/10/19 05:48 PM
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rshaw125 Offline OP
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A buddy of mine had persistent misfires on his Taurus. Compression test showed two weak cylinders. He pulled the head and laid it on it's side. Filled the ports with water after a few minutes a tiny dribble out of one valve. 1 of 6 intake valves. DOHC Ford. Then exhaust side . Two valves with little dribbles after a few minutes. Are these little dribbles enough to cause the misfire and low compression? The engine has around 150,000 miles. Is this just normal wear??


2012 Porsche Carrera S
2016 Ford Edge 2.0
2002 Taurus Vulcan SOLD
2006 Explorer SOLD
Re: Head with leaky valves advice needed [Re: rshaw125] #5007142 02/10/19 05:56 PM
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46Harry Offline
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Since the head is off and there is leakage from the valves, now would be a good time to get the head reconditioned especially since the engine has 150,000 miles on it.

Re: Head with leaky valves advice needed [Re: rshaw125] #5007153 02/10/19 06:02 PM
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KneeGrinder Offline
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Pouring water in the combustion chamber now? Yes it will show the leaking valve seats if they a fairly bad. Will cause lower compression, yes, but he really should have done a comp test before removal. compression is often lost thru rings or valves. At this point he is in no man's land till he has a valve job done and mounts heads back on motor. Yes, seems like fairly normal wear for a Taurus....

As for valves causing misfire? IDK, If its the intake, and they leak bad enough, yes. The ECU should show a code for misfire if its OBD2, and its the ignition system. Atleast it should...If its back firing thru an intake valve, probably is not going to log a code.

O'pps my bad, he did a comp test, sorry! Nice German car you have by the way! I approve...

Last edited by KneeGrinder; 02/10/19 06:05 PM.

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Re: Head with leaky valves advice needed [Re: rshaw125] #5007170 02/10/19 06:12 PM
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rshaw125 Offline OP
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Thanks for the replies. Yes a compression test revealed the weak cylinders. Wet and dry. Rings are tight. After codes for misfires. The leakages are just dribbles. i was expecting a flow of water. No obviously burned valves.


2012 Porsche Carrera S
2016 Ford Edge 2.0
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2006 Explorer SOLD
Re: Head with leaky valves advice needed [Re: rshaw125] #5007212 02/10/19 06:53 PM
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StevieC Offline
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There could be different reasons. Slightly bent valve, weak valve springs, worn seats.
Best to take the head in and have it rebuilt and put it back on.


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Re: Head with leaky valves advice needed [Re: StevieC] #5007259 02/10/19 07:22 PM
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mattd Offline
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What exactly were the compression test results? Valve leakage can certainly cause misfires


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Re: Head with leaky valves advice needed [Re: rshaw125] #5007275 02/10/19 07:32 PM
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rshaw125 Offline OP
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The two bad cylinders were 55 and 65 PSI. The good cylinders were 145 - 155.


2012 Porsche Carrera S
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2002 Taurus Vulcan SOLD
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Re: Head with leaky valves advice needed [Re: rshaw125] #5007300 02/10/19 07:54 PM
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DeafBrad Offline
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I don't claim to be a professional mechanic or anything. But what is a dribble with water should be significant when the air is under compression.


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Re: Head with leaky valves advice needed [Re: DeafBrad] #5007332 02/10/19 08:19 PM
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Chris142 Offline
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Originally Posted by DeafBrad
I don't claim to be a professional mechanic or anything. But what is a dribble with water should be significant when the air is under compression.

Yep. If liquid will pass air will really leak past.


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Re: Head with leaky valves advice needed [Re: rshaw125] #5007363 02/10/19 08:50 PM
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Linctex Offline
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Originally Posted by rshaw125
Are these little dribbles enough to cause the misfire and low compression?


Little dribbles after several minutes?

No - - Those will not affect the way the engine runs.

I have seen heads where liquid would almost run out as fast as it poured in - - STILL, no misfires!

But you could SURE hear the whistle in the exhaust when cranking it to start it!!!!!!


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Re: Head with leaky valves advice needed [Re: rshaw125] #5007366 02/10/19 08:51 PM
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Linctex Offline
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Originally Posted by rshaw125
The two bad cylinders were 55 and 65 PSI. The good cylinders were 145 - 155.


You should have done a "DRY" test followed by a "WET" test.

I honestly do not think the head is your problem, if you got "Just a tiny dribble" after several minutes.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Head with leaky valves advice needed [Re: rshaw125] #5007405 02/10/19 09:18 PM
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Trav Offline
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Sure, numbers like that can and do cause misfires, under 90 psi can cause it and the lower it goes the greater the odds. That kind of leakage is enough to cause the low compression.
Seeing as a wet and dry test was done I think you found the issue.

Edit: You should check the valve guides and cam lobe/lift also, worn guides can cause erratic seating in the running engine and worn lobes can cause low compression, a dial indicator is be the easiest way to tell on a cam in block engine.

Last edited by Trav; 02/10/19 09:28 PM.

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Re: Head with leaky valves advice needed [Re: DeafBrad] #5007451 02/10/19 10:14 PM
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KneeGrinder Offline
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Originally Posted by DeafBrad
I don't claim to be a professional mechanic or anything.

"But what is a dribble with water should be significant when the air is under compression."


Correct!


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Re: Head with leaky valves advice needed [Re: 46Harry] #5007613 02/11/19 07:24 AM
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demarpaint Offline
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Originally Posted by 46Harry
Since the head is off and there is leakage from the valves, now would be a good time to get the head reconditioned especially since the engine has 150,000 miles on it.

+1 And in all honesty if he plans on keeping the car he might as well do the other head, and check the cam.


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Re: Head with leaky valves advice needed [Re: rshaw125] #5007617 02/11/19 07:35 AM
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Donald Offline
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Originally Posted by rshaw125
Thanks for the replies. Yes a compression test revealed the weak cylinders. Wet and dry. Rings are tight. After codes for misfires. The leakages are just dribbles. i was expecting a flow of water. No obviously burned valves.


What was done to determine "rings were tight"?

What year Taurus?


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