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Second Generation Legend (1991-1995)

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Old 05-01-04, 05:18 PM   #1 (permalink)
 
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head gasket theory

so i was talking to a co-worker who is a skilled mechanic and former Jaguar emplyee and we were discussing why most head gaskets blow and his theory was because of the "stretchy" head bolts that acura and most car manufacturers use these days. he was saying that over time these bolts lose their strength and seal, allowing the gasket to leak. u can't re-tighten them when they are on or they will snap. and usually they arent re-useable. (correct me if i'm wrong).

So he was saying, what he has done with all of his cars that he has owned since the 60s is imeadiatly replace the head bolts with performance cold-forged bolts like ones made by ARP:

http://www.arp-bolts.com/pages/produ...headstuds.html

These bolts are super strong, re-useable and tighten super strong and will not lose their seal. he said that once u install these u will never have to worry about head gaskets blowing.

is this true?

also, i mentioned the copper head gaskets that didn't work and he was saying that in europe they use asbestos in their copper head gaskets and that seals properly, but its hard to use asbestos here because of north american laws.

what are your guys thoughts on these theories? I wish I would have repalced my head bolts before my head gasket blew (would have saved me tons of money!). well, of course u have to keep up on changing the coolant as well...but thats a different story
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Old 05-01-04, 06:09 PM   #2 (permalink)
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you can retighten them, and they are reusable. Mine right now are torqued at 61lbs, stock is 56. the key is to overtorque them when ur resuing them
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Old 05-01-04, 06:12 PM   #3 (permalink)
 
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yah but see your head gasket blew once and then u re-torqed. in order to precent the head gasket from blowing in the first place u would have had to keep re-torqing every how ever many thousand miles. and eventually they will snap after so much torquing.

if u had the strong bolts in the head in the first place, torqed once strong, then you wouldnt have had to replace your HG and then over-torque.

why do u think people have had the HG go twice or more ont hem over time?
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Old 05-01-04, 06:17 PM   #4 (permalink)
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u dont have to retorque them again and again, its only a one time thing. and u dont want to torque them over 64lbs, have it arnd 60 and you shuld be fine. BTW new head bolts are PRICY stick with stock, overtorque (after a HG job) and you should be fine. People whose heads have gone twice or so, have normally not had the job done right the first time. And you will find there are very very few people who have had it go twice on them.
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Old 05-02-04, 02:37 AM   #5 (permalink)
 
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It is good practice to replace critical engine fasteners on a rebuild or major repair, and the head bolts would certainly qualify as major fasteners. Overtorquing a bolt or stud can "neck" or stretch it, and it will no longer do the job it was designed to do. Going to 61 instead of 56 or whatever will probably do no harm.

Some mechanics believe it is good practice to re-torque head bolts or studs after the car has been warmed up and cooled down once or twice. Extra work, but perhaps good insurance, as some gaskets do shrink in use, and metal changes shape when heated and cooled.

Having said that, I still think the main causes of HG problems with our cars are:

1. Failure to change coolant regularly (leads to corrosion), and
2. Overheating, due to rad/hose failure, or air in the cooling system.
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Old 05-02-04, 02:45 AM   #6 (permalink)
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Here's my theory that I discussed with a long time Acura tech. There's a few reasons why the Legend engine blows head gaskets.

Theory #1. The Vibration effect - once you remove the heads, you'll notice that the cyilnder walls sit out in the open by themselves with the coolant jacket surrounding it. No structural support at the top of the cylinder walls. What we discussed was the fact that engines vibrate, and the vibration eventually eats away at the gasket allowing coolant to flow into the cylinder. Typically it does this more at the rear of the engine (#3 and #6 cylinders). Next time you're in your car, rev it up to about 1500-2000 RPM's and feel the vibration that I'm talking about. Think about that vibration happening for 100k-150k miles and how that affects this area of the engine.

Theory #2. Improperly torqued heads - We talked a little about overtorquing heads and he claims that he overtorques the C32a heads to 59-60 lb ft. The theory is that when the engines were built at the factory, the engineers of the C series engines underestimated the torque specs for the heads. The factory torque spec should have probably been 60-62 lb. ft.

Theory #3. Non-Honda coolant - Basically any non-Honda coolant can cause deterioration of the head gasket. See this post for more info: https://www.acura-legend.com/vbulleti...=honda+coolant
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Old 05-02-04, 04:04 AM   #7 (permalink)
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Old 05-02-04, 04:07 AM   #8 (permalink)
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do u think it would be a good idea to overtorque the heads before a BHG?
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Old 05-02-04, 04:45 AM   #9 (permalink)
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Quote:
Originally posted by misdeismo
do u think it would be a good idea to overtorque the heads before a BHG?
No, because not all C32A's have blown head gasket problems. I'm thinking that when the engines were being built in the assembly line, that some fool was using an uncalibrated Torque wrench. Another theory of mine.

I overheated the crap out my 92 sedan one day and to this day the guy that bought it doesn't have any head gasket problems. Making me think that not all the engines have this problem
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Old 05-02-04, 04:47 AM   #10 (permalink)
 
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Quote:
Originally posted by misdeismo
do u think it would be a good idea to overtorque the heads before a BHG?
Do you mean to re-torque the head bolts on an engine BEFORE there is any sign of a blown HG??

I think to do this, you'd have to drain all the coolant, then release the bolts, then re-torque them in the proper sequence.

I think I'd stay away from this, as I think it could lead to all sorts of problems.
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Old 05-02-04, 04:54 AM   #11 (permalink)
 
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Quote:

Theory #1. The Vibration effect - once you remove the heads, you'll notice that the cyilnder walls sit out in the open by themselves with the coolant jacket surrounding it. No structural support at the top of the cylinder walls. What we discussed was the fact that engines vibrate, and the vibration eventually eats away at the gasket allowing coolant to flow into the cylinder. Typically it does this more at the rear of the engine (#3 and #6 cylinders). Next time you're in your car, rev it up to about 1500-2000 RPM's and feel the vibration that I'm talking about. Think about that vibration happening for 100k-150k miles and how that affects this area of the engine.
After watching my buddy do the BHG job on the wifes Legend.... I firmly believe this is the #1 reason for the BHG problems on these car..... very wierd design. Those cylinder walls probably vibrate just like a tuning fork and slowly wear away the gasket, and from looking at how the gaskets looked when we removed them.... I really believe that is the cause.

I also agree with some heads not being torqued correctly from the factory.....

The one reason I cannot fully accept in the "Honda" coolant thing..... I have read all the links and stuff..... I am not saying no..... but I find it hard to believe.
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Old 05-02-04, 05:09 AM   #12 (permalink)
 
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so no one thinks that my idea of using non-stretch bolts liek the APR ones would help anything?
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Old 05-02-04, 05:41 AM   #13 (permalink)
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Quote:
Originally posted by 67GTONUT

The one reason I cannot fully accept in the "Honda" coolant thing..... I have read all the links and stuff..... I am not saying no..... but I find it hard to believe.
I really want to do a test, take a set of head gaskets and soak one in Honda coolant, and the other in Prestone, or Zerex. and see which one breaks down the fastest. Maybe do it over 60 days and take pictures of it every 10 days. I know that's probably not the proper way to test it, but I'm sure it would show something.

Quote:
Originally posted by Vancouver_Legend
so no one thinks that my idea of using non-stretch bolts liek the APR ones would help anything?
The bolts need to stretch to gain proper torque. If you used non-stretch bolts, chances are you could rip the threads out of the block. You would also have to figure out a new torque specification because putting 56 or more lb. ft. of torque on non-stretch bolts could squeeze the head gasket too tight, where the stretch bolts give just a little slack. There are pros and cons to it, I would call ARP and ask the pros.
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Old 05-02-04, 02:47 PM   #14 (permalink)
 
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Quote:
Originally posted by Mike Diaz
Here's my theory that I discussed with a long time Acura tech. There's a few reasons why the Legend engine blows head gaskets.

Theory #1. The Vibration effect - once you remove the heads, you'll notice that the cyilnder walls sit out in the open by themselves with the coolant jacket surrounding it. No structural support at the top of the cylinder walls. What we discussed was the fact that engines vibrate, and the vibration eventually eats away at the gasket allowing coolant to flow into the cylinder. Typically it does this more at the rear of the engine (#3 and #6 cylinders). Next time you're in your car, rev it up to about 1500-2000 RPM's and feel the vibration that I'm talking about. Think about that vibration happening for 100k-150k miles and how that affects this area of the engine.

s=&threadid=21171&highlight=honda+coolant[/url]
So, the cylinders are free to move at the top of the block (Deck). These are steel barrels, cast into the aluminum block I assume. Perhaps the Honda engineers figured that the heads would "grip" the tops of the cylinders (sort of an interference fit when the heads were torqued).

Interesting. Now what I'm curious about is whether other manufacturers use similar designs, and if so, whether they have problems with head sealing at the cylinders. Any more info on this?
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Old 05-02-04, 06:18 PM   #15 (permalink)
 
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Quote:
Originally posted by Vancouver_Legend
so no one thinks that my idea of using non-stretch bolts liek the APR ones would help anything?
i do, but i think a shim in the head when you do a gasket change would help more.
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