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Step-By-Step 420a Head Gasket Replacement Tutorial?

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RallyEclipse98

15+ Year Contributor
967
28
Jul 31, 2007
Dallas, Texas
Next month I will be replacing my head gasket on a good ol' 420a. Are there any good instructions out there for completing the process? The DSM factory service manual is okay but no could use more verbage/actual photos. Should I buy a haynes or chilton's? Not sure they would be any better.

Any advice?
 
Well, being I can't find any how-to's out there it must be about as simple as you say. Most people however act like it is about the most difficult repair you can do on a car.
 
I would take a headgasket job on a turbo dsm over a 420a ANY day. There is SO little room on the (420a) timing belt side of the motor. Manipulating the motor mount situation will be your friend. Download the factory service manuals and that will give you most of the info you need.

Oh, and here's a tip w/ the motor mounts. To get the passenger motor mount out after it's been unbolted from the block, unbolt the rear mount and use a jack to push the motor up and forward. You're welcome. (That wasn't my idea, by the way.)
 
It is a lot of time and work to get to the middle of the motor to replace the head gasket, so naturally a lot of people do not like that job. Make sure you clean the block good and have the head checked, you don't want to have to do it twice. There are some good threads on here about the proper way to clean your block, but a flat razor worked fine for me, using a felpro mls I got the thicker one they offer.

When I did mine on my RS I had the infamous head gasket leak from the driver side rear. If yours is the same make sure you get a new OEM bolt and cut it down a mm or two on that spot atleast. I did mine twice because of this.

Follow the FSM and you'll be golden, i
 
It is a lot of time and work to get to the middle of the motor to replace the head gasket, so naturally a lot of people do not like that job. Make sure you clean the block good and have the head checked, you don't want to have to do it twice. There are some good threads on here about the proper way to clean your block, but a flat razor worked fine for me, using a felpro mls I got the thicker one they offer.

When I did mine on my RS I had the infamous head gasket leak from the driver side rear. If yours is the same make sure you get a new OEM bolt and cut it down a mm or two on that spot atleast. I did mine twice because of this.

Follow the FSM and you'll be golden, i

My 420a was built in May of '99 and Chrysler (supposedly) fixed the bolt hole depth by then. This is the first head gasket to go on the car and it's at 175,000 so I believe they did fix the problem. Most 420a head gaskets seem to cause problems around 100k...
 
Thanks for the link, OZ. I am confident doing the timing job (especially after your link) but the head gasket still seems a bit murky. You will probably find me back here asking questions as I move along in the process.
 
Timing belt cover will be a PAIN, and everything else on the passenger side. Also make sure you keep track of all your bolts, you don't want to finish the job only to find you have more than you started with.
 
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