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Discussion Starter #1
I've owned a low mileage 1995 Lincoln Mark VIII LSC for a couple of years and it's developed an intake manifold leak that's causing me to fail CA smog.

Are there any gotchas I need to know about doing an intake gasket on this car?

I've also got codes for both O2 sensors but I don't know if those are failure points on this car or just bad codes. The exhaust manifolds may be leaky as well.

The car runs fine but it jumps a few hundred rpm at idle to compensate for the extra air in the system.

I like the car but I've had trouble getting people willing to work on it so...I guess I'm working on it since California's answer to pollution is crushing cars
 

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It’s very straight forward on the DOHCs since they are dry intakes, eg no coolant to spill. Your vacuum leak source could be from the IMRCs since the shaft for the butterflys seal with a series of O rings, and there are also top and bottom gaskets for them (manifold to IMRC, IMRC to cylinder head)


The O2 sensor codes could be reflecting the vacuum leak but if they’re original it would be a good idea to replace them with fresh ones anyway.
 

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It’s very straight forward on the DOHCs since they are dry intakes, eg no coolant to spill. Your vacuum leak source could be from the IMRCs since the shaft for the butterflys seal with a series of O rings, and there are also top and bottom gaskets for them (manifold to IMRC, IMRC to cylinder head)


The O2 sensor codes could be reflecting the vacuum leak but if they’re original it would be a good idea to replace them with fresh ones anyway.
AFAIK everything is original on this 120K car minus the suspension (replaced with conventional springs) so yes they're probably due. I can "see" the vacuum leak by spraying starter fluid near the passenger side intake and listening.
 

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It’s very straight forward on the DOHCs since they are dry intakes...Your vacuum leak source could be from the IMRCs since the shaft for the butterflys seal with a series of O rings, and there are also top and bottom gaskets for them (manifold to IMRC, IMRC to cylinder head....
What consumables do I need for the install, just regular RTV sealant to hold it in place when I bolt it back in? There are several semi-unobtainium seals on the "coolant crossover tube" alone (the wet part that needs to come out)
 

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IIRC, all the 'seals' on the crossover are O-rings.

Remove, and take to the parts store.

The IMRC bearings are sealed bearings, but they have a rubber seal; the ones from my 98 engine were gone, you may need to replace them.

I bought bearings from VXD; measure the ID, OD, and width, and look them up. You want Sealed bearings. :)
 

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Discussion Starter #7
IIRC, all the 'seals' on the crossover are O-rings.

Remove, and take to the parts store.

The IMRC bearings are sealed bearings, but they have a rubber seal; the ones from my 98 engine were gone, you may need to replace them.

I bought bearings from VXD; measure the ID, OD, and width, and look them up. You want Sealed bearings. <img src="http://forums.tccoa.com/images/smilies/vb2_smile.gif" border="0" alt="" title="Smile" class="inlineimg" />
Glad to hear that there is a non-oem solution, I had no specs so I found the one Ford dealer in 50 miles that had a pair. I am not seeing a leak at the throttle body now but if it happens I'll follow your advice.

Sadly this is a common theme in cars. People complain that they don't last, but the ones that do still don't because some dumb part hasn't been in stock since forever ago and won't be ever again.
 

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The IMRC's aren't part of the throttle body; they are between the intake and the head.

They open at ~3500 rpms, to change the runner length in the intake, for better performance at higher RPMs.

The TB butterfly bearings also have seals, and also go bad, but that's a different part.
 

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Oh? I was told differently, thanks for the 411
Don’t hate me, but it looks like I may be wrong. My DOHC’s coolant crossover has its mounting ears on top of the alternator, allowing for manifold removal without messing with it, but the older crossovers have ears further back and seem to mount on the manifold flanges sharing its mounting studs. Unless there’s room to slide the manifold back an inch or so to get out from under the crossover, the crossover would unfortunately need to come off.


Here’s a seller with a complete seal kit https://www.ebay.com/itm/1993-1998-Lincoln-Mark-VIII-Coolant-Cross-Over-Pipe-Seal-Kit-O-Rings-32V-4-6L-/223337993056?_trksid=p2385738.m4383.l4275.c10
 

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I need one of those too. :) That's cheap.
 

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Discussion Starter #12
Oh? I was told differently, thanks for the 411
Don’t hate me, but it looks like I may be wrong. My DOHC’s coolant crossover has its mounting ears on top of the alternator, allowing for manifold removal without messing with it, but the older crossovers have ears further back and seem to mount on the manifold flanges sharing its mounting studs. Unless there’s room to slide the manifold back an inch or so to get out from under the crossover, the crossover would unfortunately need to come off.


Here’s a seller with a complete seal kit https://www.ebay.com/itm/1993-1998-Lincoln-Mark-VIII-Coolant-Cross-Over-Pipe-Seal-Kit-O-Rings-32V-4-6L-/223337993056?_trksid=p2385738.m4383.l4275.c10
This kit is so complete it comes with an extra seal for no reason, nice. Ordered one since it comes with the top end seal Ford doesn't acknowledge exists but you definitely need to "burp" the car. The last time I did this I used a torch and vice grips.
 

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The "extra" seal goes in between the left and right pieces.

It's there. :)
 

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Discussion Starter #14
These cars come in two flavors, you must have the post-1996 one with the janky 'blend' door vs the early one with headlights you cannot replace
 

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I don't have a mark Viii, I have a mark motor that's going into a Cougar.

IDK what the hell you're talking about blend doors, that's inside the car.

The coolant crossover is 3 pieces, a left, right, and the removable cap piece.

In the later Marks, the cap piece is welded on. I have both styles.

An o-ring goes on the piece that goes in each head, one goes between the left and right sections, and one for the 'cap'.


As far as IMRC's, there are two styles; the vacuum operated type in the early cars with the intake at the back, and the electrical type with the side entry intake. I have both types sitting on the shelf in the garage.

I rebuilt the late model ones, before I decided they were too much hassle to use, and went with a Mach1 intake and C-type heads, with No IMRCs.

Actually, there could be 3 types; I've never seen a 96 engine. I was told they were a mix between the 2 and I wanted the 98 one.

I got the 93 heads and intake for free, and sent them to another Mod as a model to make longtubes with, lol.
 

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Discussion Starter #16
The "extra" seal goes in between the left and right pieces.

It's there. <img src="http://forums.tccoa.com/images/smilies/vb2_smile.gif" border="0" alt="" title="Smile" class="inlineimg" />
I'll get right on that EDM welding then
 

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I'm very familiar with that piece; for the third time, there's an o-ring in the section in the middle, where the flared end is to help it go in.

Note the long, larger section with the larger flared end, with the smaller piece slid into it?
Your screwdriver is at the other end, where it flares back down.

That's why it's included with the kit.

It pulls apart; if yours does not, it's rusted in place. That's not good.

It's designed so it can move, so that metal fatigue doesn't break it and make it leak when the aluminum expands when it gets hot. (The heads get slightly further apart when it heats up.)

I hate it that that so hard for you to understand; But we've been doing this a long time.
 

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Ah...this does indeed pull apart. The one that's currently attached to my car does not. Sorry I didn't understand at first, I've never had a car with such a thing.
 
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