Crack Head, Looking for some advice....... Options

[John]

I am of the opinion that I have 2 cracked cylinder heads but am looking for advice....

I have a basically stock 2.0L engine (euro pistons & cylinders done 12 years ago or so), and have been noticing what sounds like an exhaust leak but only when the engine is hot (after driving at highway speeds for about an hour). After the car sits for an hour or so and is started back up, there is no more exhaust leak sound.

The exhaust leak seems to be coming from the drivers side so I am assuming that the driver side cylinder head may be cracked.

I have had the heat exchanger off numerous times and tried many times to seal it up better, but the last several times, I have not noticed any black leak marks on the copper gaskets. (So I am past thinking it is a leak between the head and the heat exchanger.)

One strange note: About 10 years ago, I had a similar occurance and I had a spare head so I had new valves and seats installed in it and I put that one on. I don't drive the car very often so I don't put that many miles on it over time.

Is it common for 2.0 cylinder heads (driver side) to develop cracks?
Can they be detected and repaired?
Who does a good job at finding and repairing them?

Do spark plugs sometimes leak when hot? (Come to think of it I haven't checked them in a while....)

Any and all advice/suggestions will be greatly appreciated.

[lapuwali]

2.0 heads are indeed known for cracking, typically between the exhaust valve seat and the plug. Such cracks normally don't propogate all the way to the atmosphere, however.

Have you checked all the way along your heat exchangers and the HE/muffler joint(s) for leaks? Small cracks can expand with heat. Warm it up and run your hand along near the pipes and joints. You should feel and hear the exhaust blowing out of any leak you can hear while driving.

[Brad Roberts]

Check the plugs first.

Yes. 2.0 heads have some serious issues with cracking in the exhaust port. I have not found a person yet who can weld the area where they crack. If we do find someone.. we have over 40 pairs of heads that I need to have repaired. From the sounds of it.. you have cracked heads. I wish I could quickly locate a pic for you showing where they crack. It would be very easy for exhaust to escape to atmosphere near some of the cooling fins on the head near the exhaust port.

Oh.. also.. check to see if they are 76 2.0 heads with the air injection ports plugged.


B

[McMark]

Compression leaks between the cylinder head and the cylinder are also a possibility.

[John]

Thanks for the replies and keep em comming....

lapuwali:

I can't typically hear the exhaust leak sound while driving, but more when I come to a stop and it is idling...
Also, I only know of joints in the exhaust at the head and at the muffler flange. I don't notice any leaks at the muffler flange, and with the cooling air blowing I can't determine if there is any "extra" air leaking from the head area.


Brad:

I will pull the plugs and put new ones in just to make sure it isn't something like that. And no, they are not 76 heads with air injection ports. The original head was a 74 and the current head is a 73.

I would like to see a pic of where they do crack so I can check mine. BTW, what would be the best way to clean up a head? Bead blasting??? Once clean I may be able to check for cracks....

Mark:

I will check the head nuts for tightness. If I recall correctly, I did install the aluminum head gaskets when I installed the head many many moons ago...

[Jake Raby]

90% of 2.0 heads have cracks....

They can ALL be repaired and the head can be made stronger by welding them up to 12mm.

Call 706 613 7454 and send those heads to Len, one of my head techs... He is the best I have seen on a 2.0 head rebuild-

[John]

Well, I decided to take another look at the first head that I swapped out because i THOUGHT it was cracked when it exhibited the same problem I am having now.... (exhaust leak sound only when hot)

This head was serviced less than 400 miles prior to me swapping it out (new valve seats, new valves, new springs).

I cleaned up the combustion chambersbut found no cracks or any evidence of cracks. Where should I be looking?

When I look closely at the exhaust ports it does look like there was some leakage (both ports toward the middle of the head) it also looks to me like the heat exchanger ear made contact with one exhaust stud boss.

I am attaching some pics below...

[John]

Pic 2

[John]

Pic 3

[John]

Pic 4

Notice the carbon at the exhaust ports (where the copper gaskets go).

Also notice on the right (#1 cyl) shows the contact made with the heat exchanger ear.

[John]

pic 5

[John]

Now I may be right back to square one, not knowing what is making the exhaust leak only when the engine gets hot.

Are the stainless heat exchangers more prone to leaking when hot? Are the stainless heat exchangers more likely to leak period?

I may be able to find an old stock set of pipes and rip the rusted exchanger boxes off of them to see if they leak like my current stainless ones. I know the originals were made of heavier wall tubing and the mild steel will probably creep less when hot.

Any suggestions as to what I should try next???? (IMG:style_emoticons/default/idea.gif)

[MarkV]

Cold, warm & hot compression test ???

[John]

Cold, warm & hot compression test ???

I have always suggested to others not to pull plugs out of a HOT aluminum head.

How do yo do it hot without galling threads?

[MarkV]

Good question, hadn't thought of that.

[John]

Well i put my compression tester on my engine tonight and got some numbers.

I first did it cold

All plugs out, throttle wide open:

#1 155PSI
#2 157 PSI
#3 152 PSI
#4 155 PSI

My gauge has marks every 5 PSI, so the ones in between are guesstimates.

Warm but no exhaust leak sound yet (After running about 10 minutes with finger tight plugs).

#1 160PSI
#2 162PSI
#3 160PSI
#4 160PSI

I think the numbers are all very very good. The engine probably only has 5000-6000 on it since I rebuilt it 12 years ago.

I'm still looking through my parts trying to locate a stock set of heat exchanger tubes (heat boxes are probably gone).

I may also try cutting the stainless ears off and lowering them about 1/4" to space them a little further away from the heads and checking for cracks while I'm at it.

[Brad Roberts]

The cracks in the 2.0 heads that we worry about are the ones buried in the exhaust ports. The TIG guy's tell me it is impossible to weld inside the exhaust port because they have no way to keep the gas inside the port with the tungsten hanging halfway into the port.

Your pics are taken from too far away. I need good close ups of the exhaust.

Just from what I see right now, it was just a copper gasket leak.

The SSI's that leak usually have a problem where somebody has welded the tabs back on in the wrong place (in the past). Find the HE that came off that head and inspect it. I'm betting the mounting ears are bent up.


B

[John]

Brad, which view? I can always take more pics....

Looking into the port from the copper gasket side, or looking into the port from the valve seat side?

Where do they typically crack? Near the copper gasket or near the seat?

I am also of the opinion that the ears on the heat exchangers are probably bent up (or are positioned too close to the end of the heat exchanger pipe) and or the tubes are cracked at the ear weld joints.

[Brad Roberts]

They crack going away from the seat in the exhaust port. I have also seen them crack in the short turn radius.

The fab guy next door to the shop build a special jig just so he could repair SSI's for us. I gave him a brand new one to jig off of. That is how bad I find them. People just OVER torque them and bend the ears. I cant count how many times I have found TWO copper gaskets on top of a SSI HE.


B

[RustyWa]

I've heard it's also a good idea to take a large file to the SS HE tubes. I used a black marker on the ends of the face of the tubes where they connect to the heads. Take the large file to BOTH tubes at the same time and slowly file them square to each other. When the black is all gone, they should be pretty square.

I did it to mine and it worked pretty good.