How Hard to Remove Rear Head-3.8?

[Benesesso]

Found only 75 psi in cyl. no.2 in back. Other cyls. are ~120. No oil/water mixing--so far, and the engine doesn't burn oil. I'm hoping it's just a valve. For those who have pulled the rear cyl. head, how hard a job was it. Local dealer wants $1850 including valve job and new gaskets.

[iceman2]

Originally Posted by Benesesso

Found only 75 psi in cyl. no.2 in back. Other cyls. are ~120. No oil/water mixing--so far, and the engine doesn't burn oil. I'm hoping it's just a valve. For those who have pulled the rear cyl. head, how hard a job was it. Local dealer wants $1850 including valve job and new gaskets.

I just finished mine, very time consuming, cost me about $500, including new plugs, wires, and pressure checking and planing heads. Go to http://www.automotiveforums.com/vbul...d.php?t=321467 for how to tear down engine.

[LMP]

.....well....beside this 75 psi.....and given how difficult it is just to reach the spark plug or simply remove the plug wire, are you sure you had a tight fit?.....anyway, are there other symptoms that would force you to go to that lenght?....with the 60° 3.1/3.4, there is still some room to reach the rear head bolts....but I've no idea with the 90° 3.8..in fact, seems out of reach..........

[Benesesso]

Here's "The rest of the story". After 2 different dealers couldn't find anything wrong, other than the apparent 75 psi in #2 cyl., I thought more about the crummy performance. I knew the rear spark plugs had ~35k-40k miles, and I thought I had put in NGK platinums way back when I first bought the van, in 1999. It then had ~65k miles. However, the "usual" test for plugs is that if they fire OK at full throttle (worst case), they are A-OK. My van ran fine at WOT--it was part throttle that was crummy.

About 2 years ago I changed the easy-to-reach front plugs, and since I didn't know how bad the horrible Bosch platinums were then, that's what I installed. So, last Saturday I bought 6 new NGK iridiums, and started plug changing. The worst part by far was getting the plug wire off #2 cyl--pass. side rear. There is just no room to get any wrist leverage while holding the plug wire boot. Finally I heard it pop off, and the rest was somewhat easier. Turns out I had installed REGULAR NGK's, and even tho I had set the gaps ~.040" instead of the .060" specified, the gaps had opened up to ~.080", and the center electrodes were well rounded.

I trashed the Bosches and the old NGK's, gapped the Iridiums to .040", sprayed dry moly lube on the threads, and screwed them back in. The plug that came out of #2 (75 psi-?) was only slightly darker than the rest of them--very light tan vs. near white.

Fired it up and it now runs like new! I suspect the computer somehow keeps track of the voltages required to fire the plugs, and when it senses higher voltages it apparenly causes misfiring. The ignition coils are able to fire an .080" gap and crummy Bosches under heavy load, so I think the computer is somehow involved.

[LMP]

Thanks for the details..always interesting.
My experience with my other car (Kia Sportage): the car misfired badly: I took spark plugs off, and the gap was in fact quite large: resetted closer, then reinstalled everything: misfire is gone. Higher voltage needed to fire a wider gap , although the coil can generate it, can overwhelm ignition wires of tired coils insulation, hence spark is lost elsewhere.
Just lately, had to change Transport plug wires for same reason...I removed the exhaust shield to access the rear wires (from under) ...and I should have also lowered the subframe by unbolting the rear 2 bolts...just like I did last year to change the spark plugs: 1 1/2" extra clearance is welcome.