454 L29---Head Gasket Reliability

[RedBurb]

Scalped a fine running 7.4L 179K mile engine today in order to find and eliminate the source of coolant leaking into the oil. The old intake gaskets were indeed leaking as this forum frequently cites.

The intake manifold is now laying flat on the workbench awaiting tomorrow's cleaning and new intake gaskets.

What I haven't found here (yet) is information regarding the reliability of the L29's head gaskets. Does anyone have thoughts or experiences with the head gaskets? Specifically I'm wondering whether they are also prone to water leaks or are they rock solid? The head gaskets might be originals from '97.

I'd like to avoid sewing a scalp back on only to rip it off again. But needless beheadings offend more.

 

[someotherguy]

The Vortec small blocks are the engines notorious for intake gasket leaks. The big blocks -somewhat- known for it. I don't think I've seen hardly any reference at all to people having to do head gaskets on them.

Now, lifters, cam, distributor, injectors, FPR.. weak areas on high-mile examples. I had one that probably could have benefited from a valve job around 200K+ but it was a seriously neglected engine that came out of a truck that was worked nearly to death.

Richard

 

[454cid]

How much coolant in the oil? Big Blocks usually leak externally, not internally, at least not much, in my case. Most other people I've read about have the leak in the same spot I do....passenger side front where the intake head and block come together.

I've never had my heads off.... intake gaskets leak yes (likely since new) and it still leaks. I had the intake done once, and it was apparent a few weeks later that the mechanic didn't know what he was doing. I've got work off for two weeks and I may do it myself, but I've got lots of other stuff to consider too, so I may not get to the intake gaskets.

I used to regularly overheat my engine long ago when the original water pump went bad, and I didn't have time to fix it. It's fine.

I have almost 300K miles now. In short, don't pull the heads unless you're bored.

BTW, they're almost 75lbs each.

The stuff that GM says to put on the intake bolts isn't a black goopy stuff like "my" idiot mechanic used. The part number crosses over to Loctite according to what I've read online. I found the intake bolt closest to the leak to be less than hand tight just a couple of weeks after gasket replacement.

 

[RedBurb]

How much coolant in the oil? Big Blocks usually leak externally, not internally, at least not much, in my case. Most other people I've read about have the leak in the same spot I do....passenger side front where the intake head and block come together.

I've never had my heads off.... intake gaskets leak yes (likely since new) and it still leaks. I had the intake done once, and it was apparent a few weeks later that the mechanic didn't know what he was doing. I've got work off for two weeks and I may do it myself, but I've got lots of other stuff to consider too, so I may not get to the intake gaskets.

I used to regularly overheat my engine long ago when the original water pump went bad, and I didn't have time to fix it. It's fine.

I have almost 300K miles now. In short, don't pull the heads unless you're bored.

BTW, they're almost 75lbs each.

The stuff that GM says to put on the intake bolts isn't a black goopy stuff like "my" idiot mechanic used. The part number crosses over to Loctite according to what I've read online. I found the intake bolt closest to the leak to be less than hand tight just a couple of weeks after gasket replacement.

454cid ---I initially became aware of the coolant leak during a DIY oil change. My phone happened to ring after two or three turns into the loosening of the oil pan bolt. Instead of ignoring the call I stopped and answered (Squirrel!). The upshot being that during the interuption I became aware of many individual thin brownish liquid droplets dripping off the partially loosened bolt (whereas oil falls along thick sphagetti like strings). Long of the short this thin liquid was coolant that had settled at the bottom of the pan below the oil. Since the initial event I've changed the oil twice at 250 mile intervals to "size up the leak" and using the same partially loosened pan bolt technique have caught 1 to 2 Dixie cups of coolant droplets before the oil string appears. So this equates to approximately 4 - 6 oz of coolant in 250 miles (or about 10 -12 days)--no bueno.

I'm leaning towards not changing the head gaskets but instead testing the fates (not bored enough ;-). Will post results in a couple of weeks. Thanks for the tip on the Loctite --I've read "Blue" is the stuff.

 

[someotherguy]

If you suspect head gasket failure at all, you can try the chemical leak test. It's that blue bottle of stuff at the auto parts with the squeeze bulb/clear tube; you put the chemical in there and squeeze up some coolant from the radiator neck (engine warmed up and running) and the chemical will turn yellow if combustion gases are present in the cooling system. It's not a 100% fool-proof test; I have been misled by a bad batch of chemical that wouldn't turn color and the engine did indeed have a blown head gasket (old TBI 5.7) but in general it's pretty reliable.

Richard

 

[454cid]

454cid ---I initially became aware of the coolant leak during a DIY oil change. My phone happened to ring after two or three turns into the loosening of the oil pan bolt. Instead of ignoring the call I stopped and answered (Squirrel!). The upshot being that during the interuption I became aware of many individual thin brownish liquid droplets dripping off the partially loosened bolt (whereas oil falls along thick sphagetti like strings). Long of the short this thin liquid was coolant that had settled at the bottom of the pan below the oil. Since the initial event I've changed the oil twice at 250 mile intervals to "size up the leak" and using the same partially loosened pan bolt technique have caught 1 to 2 Dixie cups of coolant droplets before the oil string appears. So this equates to approximately 4 - 6 oz of coolant in 250 miles (or about 10 -12 days)--no bueno.

I'm leaning towards not changing the head gaskets but instead testing the fates (not bored enough ;-). Will post results in a couple of weeks. Thanks for the tip on the Loctite --I've read "Blue" is the stuff.

Very interesting way to measure the coolant. I'll have to see what happens next time I change my oil. I do have some coolant in my oil, as I always seem to have more moisture than what the PCV system can handle. The oil fill tube has rust inside it, and during cold months it collects snot. It's the highest point, and the moisture tends to condense there. My bigger concern at the moment, is gas in the oil. I'm finally going to have to do injectors.

Since you are getting a measurable amount of coolant in the oil in a short time, I think it would be wise to do some checking before making your decision. The chemical test Richard mentioned, sounds like a good place to start. A compression test may also be of benifit... if compression is down, it's not sealing somewhere. I'm not the most expereinced person with bad headgaskets, so I'd need some guidence myself with diagnosing them for sure. The one I did have years ago was super obvious...billowing white clouds behind vehicle and a chocolate milkshake for oil. That was an Isuzu made Chevy LUV.

 

[RedBurb]

With any luck I should complete the intake gasket replacement job within the next few hours. Did I really have to write that...!? lol

Took a ton of pics of the disassembly/reassembly process if anyone is interested.

The very last step will be to drain & replace oil and filter (remove the "settle" before firing-up the beast) and flush and replace coolant. I'll probably run it for a day or two and repeat (using cheap 5w30). The Dixie cup grap sample will indicate whether Richard's suggestion is necessary. Stay tuned...

 

[Schurkey]

The stuff that GM says to put on the intake bolts isn't a black goopy stuff like "my" idiot mechanic used. The part number crosses over to Loctite

"Loctite" makes hundreds of products.

Thanks for the tip on the Loctite --I've read "Blue" is the stuff.

Loctite makes several "Blue" products. The common blue threadlocker is 242. At any rate, a threadlocker isn't what you're looking for.

The Loctite product you'd use to seal intake bolts or headbolts that go into the water jacket is one of several "PST" (Pipe Sealant with Teflon) formulations. The easiest to source, and probably the OEM equivalent is "592".

xc_hide_links_from_guests_guests_error_hide_media

You must be registered for see images

 

[454cid]

"Loctite" makes hundreds of products.

Loctite makes several "Blue" products. The common blue threadlocker is 242. At any rate, a threadlocker isn't what you're looking for.

The Loctite product you'd use to seal intake bolts or headbolts that go into the water jacket is one of several "PST" (Pipe Sealant with Teflon) formulations. The easiest to source, and probably the OEM equivalent is "592".

xc_hide_links_from_guests_guests_error_hide_media

You must be registered for see images

Although, I can't find the specific GM part number right now, the manual states to use a threadlocker..... I just looked it up. The intake bolts don't go into the water jacket.

 

[PlayingWithTBI]

The intake bolts don't go into the water jacket.

IDK about the 454 but, on a SBC they do go into the oil valley. The center ones point right at the push rods (ask me how I know, LOL). I use high temp PTFE paste on them and head bolts.