Just got a call from RRE, asking what all I knew as the causes and things to check for HG leaks on the 420A. I reported the general sequence of things as I undertstand it:

1) retorque head
2) replace headgasket (and other related gaskets)
3) check that the holes for the head bolts are deep enough. As I recall, there was one, pobably on the front right, that sometimes needs to be drilled down a smidge further (anyone know how much?) .

Is there anything else that can be said about this? I don't have the greatest memory in the world, so I'm coming to you guys to get more info.

BTW, I'll probably create a detailed FAQ out of this, as it is definitely a common issue. Send in any relevant info you may have.

juan

These cars come from the factory with a composite HG. The material isn't the greatest, and there has been talk of a rear driver's side corner bolt hole that wasn't drilled quite deep enough. I haven't been able to confirm or deny that, but when i do know is that once the headgasket is replaced with the revised part (the MLS HG from the dealer) the problem is usually solved. I don't remember ever hearing of an MLS gasket blowing, or leaking after it has been replaced.

Well, one way to solve the problem if there is a hole taht is not tapped far enough down, would be to use a set of ARP head studs. Then you can really torque the head down, and not worry about bottoming out a bolt.
-=B-=

You're supposed to use Mopar gasket spray for the MLS gaskets (p/n 04318035).

Also- there's at least 3 different head gaskets for the 420a. You want the latest MLS (4 layer) one. Pic:



Top: OEM original, graffoil type, impregnated silicone beads
Middle: Cheap OEM MLS gasket, 3 layer (rubber, aluminum, steel, aluminum, rubber). Comes in a gasket kit?
Bottom: Nice new gasket, 4 steel layers, no rubber. *Needs Mopar gasket spray*

TSB:
http://www.neons.org/neontsb/TSB/09/090598.htm

Hehe I'm assuming they are calling about Ian's car which is getting the hg replaced right now. I also think that with the MLS gasket, there shouldn't be much further issues. Hopefully not, since I have the MLS gasket now and didn't ask them to drill out that fourth hole or anything (never had a head gasket leak to begin with though).

Yeah, they are probably calling about my headgasket. I car is there right now.

I am not too impressed with their service. I brought my car in on Monday night and they don't expect the new HG parts to come-in until tomorrow (tuesday). Thats one full week for just the parts, not even any work. It is a huge inconvience for me and my mom cause i have to take her and pick her up from work everyday. I just hope i get it back on Wednesday, or i will be walking 13 miles to school.

... I have a copper mix headgasket and it requires the spray to properly seal, after that it seals. It has seen 18pounds and no leaks so it does the job. I'd like to point out though that it mostly effects early block 420a's found in the '95 and '96s. In '97 the block was updated, and though it may have little to do with the HG it seems to effect the later cars less

I had thought there was only a HG problem with earlier years of 420A's? On my 98, don't i have the improved HG? I know its prob not the MLS gasket, but isn't the one i have better than the 95-97's???

hmm i just came from rre today.. did not see ur car maybe i did not look in the right area.. dude if rre is calling juan for info that makes me wonder...

Michael 99gs
Mods:
Hrc Stage 2
S-FMU
315cc injectors
Crane HI-6DI2
Greddy Type S Bov
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Autometer Boost,
Egt,Tranny Temp Gauge & Cooler
Air/Fuel Light & Digital
Tokico Adjust Struts
Eibach Pro Kit Springs
Front & Rear Upper Bar
CarCraft Interior
Sound System= Bring it On

Hehe don't worry. They ported and milled my head, and reinstalled cam gears three times already without any problems. I think they are just wanting to make sure there are no other causes for the leak (besides having the old composite head gasket).

I've heard the reason that one bolt hole isn't deeper tha the rest ifs, that there is a coolant passage below it. So please if you do anythign shorten the head bolt a couple threads, drillign and retapping gould cause more problems that it would fix. Just in the danger of messing upi the existign threads to bad to hold alone.

Una salus victus.



Michael J. Kulaga
e-mail: Michael_97RS@2gntDSM.zzn.com aol IM: MJKulga
http://highlander.dsmpower.com/

All motor in the making.

Injen CAI, 55mm TB, P&P Intake Manifold, Hooker Header, GS-T Muffler, AFX UDP, S-AFC, 8.5mm Magnecor Wires, Crane Fireball HI-6DI2, SS Clutch Line, NRG Susp. Motor Mount Ins., FU/RU/RL STBs, TSW Blade 17x7.5, Bridgestone Potenza RE730, Front KVR Cross-Drilled Rotors & Carbon Fiber Pads

To Be Installed: P&P Milled Head, Rear Disc Brakes, Rear KVR Cross Drilled Rotors & Carbon Fiber Kevlar Pads, SS Brake Lines