- 2,020
- 24
- Nov 10, 2002
-
Raleigh,
North_Carolina
The following information I originally posted as a tech article after having gone to a couple Daimler-Chrysler Training courses for work. Since posting this I've gotten a few PM's and other forms of feedback suggesting that this information, while very detailed and straight from an "authority" on the subject, may not be in the best interest of the 1. the audience reading it on Performance Forums and 2. just may not be in the best interest of ANY engine except the latest and greatest that never had sprayed MLS's in use since day one.
Before jumping on the "Doug's a dumbass" band wagon please note all the other articles I've posted and understand that I've never posted anything that I thought was wrong and to the best of my knowledge I've never had to make a retraction. This however, I feel is not tech article worthy YET AND putting it here will allow for a discussion on the subject rather than a read-only type thread.
The bottom line is I'm being trained to NOT spray headgaskets, of any engine design or era, under any circumstances. If I spray one and it comes back for any reason then the headgasket gets called back for warranty parts claim. If they find the headgasket to be sprayed then they reject our warranty claim and I don't get paid. However, there is the mentallity that many of us share which is this: I've been spraying MLS headgaskets ever since I started and I've never had a failure, why should I change now and risk it?
The article is as follows:
When the Multi-Layer Steel Headgaskets (MLS) first started being used on the Neons and 2gnt's it was also a common practice to spray down the headgasket with a gasket adhesive similar to Copper Coat. Mopar calls their stuff "Gasket Sealant" and every dealership stocked it. However, I recently got back from a Daimler-Chrysler training class in Cam-in-head engines where we discussed the new engine coming out in 07 year models as well as previous engines currently in use. One very suprising bit of information discussed was the use of this spray on MLS gaskets and why it's NOT good to do it.
To help explain things a bit I'll explain why many manufacturers switched to MLS headgaskets in the first place. If you're old enough then you probably remember the days of all cast iron blocks and know that the only reasons why they failed were over-heating, poor design or too much power. Well, things have changed considerable and alot of it has to do with emissions and the design of the average small engine and cramped engine bays.
First there's the emissions side of things. If you've popped the hood on a variety of cars that are ten years old or newer you'll see a growing trend. Less room in the engine bay and where is that ice cold exhaust component that NEVER burns you when you're working around it? The catalytic convertor... it's getting closer and closer to the exhaust manifold isn't it? Heck, some cars have the cat and the exhaust manifold integrated in to one assembly. The idea behind this is that a cat is not up to operating temperature until it reaches about 600 degrees. Cold starts and long idle times tend to be the leading cause of emission problems in the world today. Getting that cat up to proper operating temperature quicker is the only way to reduce those emissions put out at cold starts.
If you move the cat closer to the engine then you can only heat it up quicker. This is a growing trend among car manufacturers who struggle with older engine designs that still fit current market demands but not emission standards. As a result you get the cat closer, the engine bay hotter and alot of components that need to be able to tolerate that heat. Unfortunately, this has raised demands on engine cooling systems to protect the engine from overheating on the cat-side of the block while running cooler on the opposite side. The end result there is big expansion and contraction differences in the cylinder head and block from one side of the combustion chamber to the next.
Next is the composition of the engine itself. Older engines and engine designs used all cast iron. Heavy but dependable and alot more tolerable to heat changes. On all current DSMs and in every other market out there the manufacturers put an aluminum head on a cast iron block. Aluminum cools better, is lighter and still strong. The cast iron block still does all the grunt work of the engine and has to wistand most of the pressure. The headgasket though is frequently the weakest link because it has to transfer the heat from the block to the head as well as withstand the pressure of the combustion cycles. As a result we see more and more failures of these due to extended periods of running hot, excessive combustion chamber pressures and weak spots between various sealing points.
The biggest problems for the 2gnt and chrysler 4 cylinder owners from 95 and up was the temperature change difference between the aluminum head and cast iron block. Accelerated by a cat that was a foot away from the headgasket on the back side, the softer aluminum expanded quicker than the cast iron block and the headgasket was the component in the middle. Being of a composite material it simply rubbed itself to death and began leaking.
So after all this you're probably wondering what's the big deal about an MLS anyways? Well, it moves. WFT??? Why would I want a headgasket that moves? Because it is kind of like multiple headgaskets that still seal when stacked together. When you have two metals that don't expand and contract at the same time you need a gasket the can make the transition without compromising the sealing qualities it's there for in the first place. The layers allow this to happen.
So I've talked about Catalytic convertors heating up the engine bays, Engine metal choices and also the two most common designs of headgaskets. So what about this stupid spray stuff? Well, it's glue. It is pretty cool stuff when you first hear why it was used. Imperfections in the sealing surfaces were sealed up to a certain amount by any good gasket. But this spray stuff seals up another couple of thousandths of an inch which can make the difference between blowing out and not if you've got a slightly warped or pitted head. Ultimately, you want a clean and flat surface but that's not always the case in the shade-tree world of automotive repair.
BBBBBUUUUUUTTTTTT..... Here's the problem. IT'S GLUE!!!! What happens when you glue something? IT DON'T MOVE and that's exactly what we want an MLS headgasket to do. If the bottom side of the gasket is glued to the block and the top is glued to the head then you've only got one or two more surfaces that help that transittion of heat. If you glue it in place then you've just reduced the abilities of a pretty well designed headgasket. So please put down the rattle can and step away!!
Thanks for not falling asleep,
Doug
Before jumping on the "Doug's a dumbass" band wagon please note all the other articles I've posted and understand that I've never posted anything that I thought was wrong and to the best of my knowledge I've never had to make a retraction. This however, I feel is not tech article worthy YET AND putting it here will allow for a discussion on the subject rather than a read-only type thread.
The bottom line is I'm being trained to NOT spray headgaskets, of any engine design or era, under any circumstances. If I spray one and it comes back for any reason then the headgasket gets called back for warranty parts claim. If they find the headgasket to be sprayed then they reject our warranty claim and I don't get paid. However, there is the mentallity that many of us share which is this: I've been spraying MLS headgaskets ever since I started and I've never had a failure, why should I change now and risk it?
The article is as follows:
When the Multi-Layer Steel Headgaskets (MLS) first started being used on the Neons and 2gnt's it was also a common practice to spray down the headgasket with a gasket adhesive similar to Copper Coat. Mopar calls their stuff "Gasket Sealant" and every dealership stocked it. However, I recently got back from a Daimler-Chrysler training class in Cam-in-head engines where we discussed the new engine coming out in 07 year models as well as previous engines currently in use. One very suprising bit of information discussed was the use of this spray on MLS gaskets and why it's NOT good to do it.
To help explain things a bit I'll explain why many manufacturers switched to MLS headgaskets in the first place. If you're old enough then you probably remember the days of all cast iron blocks and know that the only reasons why they failed were over-heating, poor design or too much power. Well, things have changed considerable and alot of it has to do with emissions and the design of the average small engine and cramped engine bays.
First there's the emissions side of things. If you've popped the hood on a variety of cars that are ten years old or newer you'll see a growing trend. Less room in the engine bay and where is that ice cold exhaust component that NEVER burns you when you're working around it? The catalytic convertor... it's getting closer and closer to the exhaust manifold isn't it? Heck, some cars have the cat and the exhaust manifold integrated in to one assembly. The idea behind this is that a cat is not up to operating temperature until it reaches about 600 degrees. Cold starts and long idle times tend to be the leading cause of emission problems in the world today. Getting that cat up to proper operating temperature quicker is the only way to reduce those emissions put out at cold starts.
If you move the cat closer to the engine then you can only heat it up quicker. This is a growing trend among car manufacturers who struggle with older engine designs that still fit current market demands but not emission standards. As a result you get the cat closer, the engine bay hotter and alot of components that need to be able to tolerate that heat. Unfortunately, this has raised demands on engine cooling systems to protect the engine from overheating on the cat-side of the block while running cooler on the opposite side. The end result there is big expansion and contraction differences in the cylinder head and block from one side of the combustion chamber to the next.
Next is the composition of the engine itself. Older engines and engine designs used all cast iron. Heavy but dependable and alot more tolerable to heat changes. On all current DSMs and in every other market out there the manufacturers put an aluminum head on a cast iron block. Aluminum cools better, is lighter and still strong. The cast iron block still does all the grunt work of the engine and has to wistand most of the pressure. The headgasket though is frequently the weakest link because it has to transfer the heat from the block to the head as well as withstand the pressure of the combustion cycles. As a result we see more and more failures of these due to extended periods of running hot, excessive combustion chamber pressures and weak spots between various sealing points.
The biggest problems for the 2gnt and chrysler 4 cylinder owners from 95 and up was the temperature change difference between the aluminum head and cast iron block. Accelerated by a cat that was a foot away from the headgasket on the back side, the softer aluminum expanded quicker than the cast iron block and the headgasket was the component in the middle. Being of a composite material it simply rubbed itself to death and began leaking.
So after all this you're probably wondering what's the big deal about an MLS anyways? Well, it moves. WFT??? Why would I want a headgasket that moves? Because it is kind of like multiple headgaskets that still seal when stacked together. When you have two metals that don't expand and contract at the same time you need a gasket the can make the transition without compromising the sealing qualities it's there for in the first place. The layers allow this to happen.
So I've talked about Catalytic convertors heating up the engine bays, Engine metal choices and also the two most common designs of headgaskets. So what about this stupid spray stuff? Well, it's glue. It is pretty cool stuff when you first hear why it was used. Imperfections in the sealing surfaces were sealed up to a certain amount by any good gasket. But this spray stuff seals up another couple of thousandths of an inch which can make the difference between blowing out and not if you've got a slightly warped or pitted head. Ultimately, you want a clean and flat surface but that's not always the case in the shade-tree world of automotive repair.
BBBBBUUUUUUTTTTTT..... Here's the problem. IT'S GLUE!!!! What happens when you glue something? IT DON'T MOVE and that's exactly what we want an MLS headgasket to do. If the bottom side of the gasket is glued to the block and the top is glued to the head then you've only got one or two more surfaces that help that transittion of heat. If you glue it in place then you've just reduced the abilities of a pretty well designed headgasket. So please put down the rattle can and step away!!
Thanks for not falling asleep,
Doug
.
)
he recommends not spraying it at all.
