By listening for escaping air at the throttle body, exhaust system and crankcase the cause of the pressure drop can usually be determined.

#1: If air is escaping from the crankcase breather, the oil dip stick tube or the oil drain opening in the oil pan it's the ring(s)

#2: If air is escaping from the exhaust system it's the exhaust valve which is not seating correctly

#3: If air is escaping at the throttle body it's the intake valve which isn't seating correctly.

#4: If air bubbles show up in the radiator or air is escaping from an adjacent spark plug hole then you have a leaking head gasket, a cracked block or cracked head.

Since we already know that bubbles are appearing in the radiator, we know that #4 applies. So it then becomes just a matter of pin-pointing which one of those three possibilities it is.


Here are a couple of tests to see if one of the valves is leaking:

Pressurize the suspect cylinder as before:

Remove the MAF and accordian, open the TB butterflies and just put your ear there. If the intake valve is leaking, you'll hear a hissing sound. Kind of a hollow hissing sound.

If you detect air there, then the intake valve is leaking, but don't forget you also have bubbles in the radiator. So to eliminate the intake gasket as a possible cause of THOSE bubbles in the radiator, you can fashion a metal plate to bolt across the suspect intake port using a solid gasket. Most auto parts stores sell make-it-yourself gasket material.

You'd need to remove the intake manifold, install the solid piece of gasket material and the metal plate (anything 1/4" thick or slightly thicker will do) inwhich you've drilled holes for mounting them to the head. Use sensor safe silicone sealant on both sides of the gasket material and bolt it down. What we're trying to do is seal off that intake port.

Now, when you pressurize the cylinder, if the bubbles are still in the radiator, you can bet it's not the intake gasket (because you've taken it out of the loop) so it has to be the head gasket, head or block.

Listening at the exhaust is a little harder, but the same principle applies; listen at the header tube for air passing into the header.

Air bubbles in the radiator is a sure sign of a head gasket leaking or a cracked block or head though.

BUT, I WOULDN'T STOP THERE. I'd check all the other areas just to be sure that you don't correct one source of the leak, put everything back together only to find that there is another leak somewhere. Try to detect and fix them all at one time.

Hope this helps.

Jake

 

jake you have been very helpful..update

removed intake,, constant pressure (100psi)applied to suspected cylinder #8, observation: bubbles are visable through the rear coolant passage of head that leads to intake..both valves closed
i have movie i will upload.. givie me 15 minutes to do this.

checked seal around intake ..THIS IS GOOD>>no failure there.
be back soon.

 

here is the mpeg,(movie of leaking cylinder) i added beer to make bubble appear better while under pressure
hopes it works leaking head #8

definatley leaking proceed from here?

 

Yep, the movie works.

Looks like you're on the right track to solving this.

Keep us posted on your progress.

Jake

 

update: head still on:

test each cylinder on on the pass side 2,4,6,8, weseen #8 leaking..i closer look,, all are leaking air into water passage.. ..that next is to pull heads CAREFULLY. phoned supplier suggestted that head gasket was defective...ummmm guess what... .. ok pulling head now...well may be i'll test other side first...and gues what ... tested # 3 becuz i know it at TDC.. i Can hear air bubble in the coolant passges..WHAT GIVES?????

 

jake......ummmmm...what up s ??

 

Remember, the testing you've done so far will identify a single problem area which will be the area of the greatest leakage. Let's just hope that there's only one area leaking.

Since you posted that you retorqued the head bolts, and if you're sure your torque wrench is accurate, I borrow another torque wrench and check the break-away torque of the head bolts.

I'd then pull the head and check both the head and the block for flatness and I'd also check the head gasket.

I'd also have the head pressure tested, or zygloed for cracks.

You can use a machinist straight edge and some feeler gauges to check them for flatness. Off the top of my head I won't try to post the maximum amount the surfaces can be out of being perfectly flat. I never try to commit to memory those kinds of specs.; I always look them up just to be sure. Same thing with the head bolt torque sequence.

BTW, I always use at least 6 incremental steps when torquing head bolts. 10, 25, 35, 50, 65 and 70/75, depending on what's called for.

From memory, there is a maximumn amount the surfaces can be out from being perfectly flat, but also a maximum amount within a certain distance, like 6". Again, those specs have to be researched.

I'd closely examine the head gasket to see exactly where the leakage occurred. I'd lay the head gasket on the block and see how the fire ring mates up with the bore OD. I'd do the same with the combustion chambers on the head.

The head gasket bore diameter may be too small causing the fire ring to extend into the cylinder bore or into the combustion chamber. If exposed to the heat of combustion the ring will eventually burn through resulting in leakage.

The ring should also show that it was compressed evenly around its circumference.

Hope this helps.

Jake

 

BINGO>>>>>>>>>>>READ THIS >>>>>

removed head pass side... would you believe this.. top row head bolts,gasket is out half hole out.. this is also the same on the center row of heads bolt to gasket holes. the gasket has S T R E C T E D into an oblong hole... I will take pic and upload..shortly
BTW: torgue wrench is new and calibrated .Also took bolts off with torgue wrench, they moved at 70ft lbs...

iassume that the other side is the same.. wheew i thought for sure heads...

 

Just to throw out 1 more thought...I read in a recent issue of Corvette Fever (within the last 6 months or so) about this same problem complete with pics. As I recall it delt with a bad head gasket causing the problem and some thing about a "flap" on the gasket .......or some such that would seal under low pressure but leak when the higher pressures were introduced into the cyl. The article pointed to # 8 cyl as the likely culprit. I'm not home so I can't look it up for you. Take a real good look at that gasket when you pull the head. The pics were really descriptive if you can locate the article.

 

I'm trying to figure out what could have caused that to happen.

Your block does have dowel pins in it, right?

Are you sure they are the correct head gaskets, not mis-packaged?

Can't wait to see the photos/video.

Jake

 

jake i called supplier The felpro1010 gaskets are the right fitment for this application. i believe i asked you about this a while back, THATS WHY i used them. These are the better gaskets! oh yes there are line-up up pins...and you will notice the up side of gaskets.. rember i used torgue wrench to remove bolts.. That was To MAKE sure i had torgue them down properly.. the bolts started to move at 70 ft lbs...

HAVE you seen Anything like it?

NOW for the pic... How a felpro 1010 gasket can expand under cylinder pressure...???

 

I would suggest getting new head bolts, going forward. good luck

 

oh please sent me that info...i could really use it now!...taking them back and ask them (supplier) to splain it.
thank you

 

Mike the head gasket thickness too.

I've taken Fel-Pro head gaskets off an engine that had been running for quite awhile and measured the fire ring thikcnesses. In one case that comes to mind, I found one gasket measured .0440 and the other one .0470.

We're talking .003 difference between the two of them, but ALSO .004 to .007 from what the package claimed, since they were supposed to be .040.

So if you get a certain compression reading one side of the engine of the engine and a different set of readings on the other side, check the gasket thickness too. It may not be due to uneven deck heights.

Jake

 

metal compress is . .0435....material is .052 at an egde where ther was no compression...
now if i could hold of that article... bang WE HAVE REFUND !!! .sad thing is for gaskets only....

 

What I was concerned about was mis-packaging. The package said 1010s, but, in fact, maybe something else was inside that were not 1010s.

I just saw a futureistic movie on SAT last night where a computer glitch changed a guy's name from Tuttle to Buttle (or was it the other way round?) All sorts of problems arose out of that; anyway, "shi* happens."

And that happens with a lot of companies. That's why, for example, before I leave the auto parts store, I open each and every spark plug box and physically examine each and every plug. When the claim is that the plugs are "pre-gapped at the factory" guess what I do?

Same with bearings (main and rod), etc. to make sure they are stamped as being the ones I want. Even then, I Plastigage the clearances just to make sure they weren't mis-stamped or the machine shop screwed up in their work.

Which brings to mind the Forum member who had the wrong size piston installed in his engine by a "formerly" well respected engine shop. I put up a really long (probably too long) post dealing, in part, with how important it is to examine each and every part you lay your hands on when building an engine. I don't assume that just because it's new and in an unopened package that it's right.

I've gotten wrong length lifters from Isky, on and on.

Last weekend I installed a new Melling oil pump in my 415, guess what I did? You've got it! Right out of the box, I tore that sucka apart, checked the gears, miked the end clearances, pulled the pressure spring to check the bore for burrs, etc.

I've found a Moroso Blue-Printed oil pump with a burr in the bore which would prevent the pressure spring from moving smoothly.

They way I look at it, it's the builder/installer's ultimate responsibility to make sure he's got what he wanted and that it doesn't have any defects. I'm my harshest critic.

Jake

 

Just looked at the photo. No, I've never had any do that on me before.

I saw also that it's stamped 1010 and I'm sure glad you posted that photo. I hope everyone gets a good look at it.

Fel-Pro is now off my list! I'll probably move to SCEs.

I'd like to see the article on the other similar failures too; I hope he finds it.

Since I know you're going to pull the other one too, I'd still check the surfaces for flatness; only takes a few minutes.

Finally, there's light at the end of the tunnel.

Keep us posted.

Jake

 

WELL....isnt that the way it goes. .i had the similiar problem with the heads. first they supposely rebiuld them. UH....well when i got them back they had radiused the top of the valves about a good 1/32"...this caused the rocker to fall off thier purch " so to speak" . not a good pratice.. they had to replace with 16 new valve...then i argued the fact that new seat were required.. they did this.... i didnt let it go ...i then measured the clearance on valvel giudes.. ther were out .002 " ..wobble .. guess what new guides new valves new seats. it goes on ,they felt it was not neccessary to machine surface..guess what, all this should have been done with the initial repair. but becuz they took short cuts they paid for virtaully complete rebuild of these heads , short of pressure testing..and i supplied new spring.. oh did i forget to mention that i have 2 yes 2 sets of upper head gaskets sets, from these guys.
the only thing is that trying to accomplish everything correctly, sometimes is not possible...

 

I just visited the Corvette Fever website and did a Search and also looked at all the Tech Articles they have posted there.

I didn't find the article on the head gasket problem though.

Jake

 

..all i can say is ...that i have learned and can chalk this to EXPERIENCE the next time .. i wonder if i can reuse these felpros for my big block chevy... .. hey CFI_EFI..whatcha think?