Piston Slap: to Mark VIII the Mark VII Air Suspension

by Sajeev Mehta

Published: September 8th, 2014

TTAC Commentator furiouschads writes:

A Mark VII is in my sights. I like the Mark VIII air suspension control that lowers the car when it hits 60 mph. Will a Mark VIII suspension control box work in a Mark VII?

Sajeev answers:

WOW: you mean someone actually can afford to spend the $300-2000 in new/used/aftermarket/OEM replacement parts to make a functional Lincoln air suspension system on a fully depreciated hooptie? You mean someone else out there doesn’t pigeonhole these systems with the nightmares made by manufacturers in a more European locale?

So sure, why not lower a Mark VII air suspension at speed? I poked around the wiring diagrams for a 1988 Mark VII and 1993 Mark VIII and wasn’t totally horrified at what I saw. Matter of fact, I’d be tempted to integrate the 1982-83 Fox Continental variable ratio steering system into it, as the Mark VIII’s air suspension “control box” also controls its speed sensitive power steering.

But being a complete Fox Body geek isn’t a great idea —welcome to my hell!– and adding the Mark VIII’s lowering capabilities is already challenging.

piston slap to mark viii the mark vii air suspension

1988-1989 Mark VII LSC

It isn’t easy because the Mark VII air suspension is a different beast: boasting the same number of ride height sensors (two front, one back) but each sensor has an extra (4th) wire. The reason escapes me, as someone ran off with my Mark VII service manual. While it might be possible to convert to Mark VIII sensors, hopefully that isn’t necessary.

The “hard” part is actually the easiest: the lowering feature comes via communication to the VSS (vehicle speed sensor), readily available at the engine computer (in the kick panel, tough) or speedometer (easy).

If you get a Mark VII that isn’t hopelessly in need of attention, get a Mark VIII suspension computer and mock it up. After you get the shop manuals for both and do a good job with RTFM…son!

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

#AirSuspension #Bag #Computer #Conversion #Fn-10 #Fox #Highway #Lincoln #Lower #Mark7 #MarkVIII #Mn-12 #Retrofit #MarkVii #Processor #SpeedSensor #Mark8

Sajeev Mehta

More by Sajeev Mehta

Comments

Join the conversation

7 of 43 comments

Relton on Sep 08, 2014

As usual, there are lots of posters here who don't really know anything about air suspension. Most of the Ford horror stories are the result of people trying to fix a system they know nothing about. Often expensive parts are replaced when all that is needed is a retaining clip on the link from the axle to the sensor. A common problem on the rear axles of Town Cars and Continentals. Millions of Fords have air suspension that works so well the owners don't even know they have it. Every year, millions of perps ride to the slammer in Ford cop cars with rear air suspension. Millions of Ford SUVs are driving around with completely functional air suspensions. And, now, over half a million Ram trucks & Grand Cherokees have left the factory with air suspension. Really, if air suspensions are such a bad idea, why does every tractor trailer and transit bus have an air suspension? Busses since the 50s. Not to mention nearly every high end car, and lots of special off-road Jeeps. As far as grafting Mark VIII computer systems to a Mark VII, I suspect that it would be a major project. I think the VIII has a different set of protocols than a VII. I am sure that the later VIIIs are different than the first VIIIs. If you want to change the height manually, it is relatively easy, conceptually, t wire a resister either in series or in parallel with each sensor (here you have to read the manual. I can't remember whether the resistance increases or decreases with a height increase). Then wire a bypass switch around the resistors. When the resistors are bypassed, the system will maintain the standard ride height. Flip the switch and the ride height will change. If you just want to lower the car, you can simply adjust the length of the links to the sensors. Either way will retain the constant height and constant ride frequency of the air suspension. There used to be a company, All American Air, that made parts for Lincolns, and was run by a very competent guy. I haven't messed with Lincolns for a few years now, so my memories of specifics isn't what it used to be. I've said this before, but my experience with Fords is that their steel springs fail quite often, much more than their air suspensions fail. Google "Taurus front springs", for example. The MN-12 cars, in northern climates, also suffered broken springs. Parts places used to keep them in stock. Bottom line: keep the air.

Like Reply
- See 4 previous
- Jacob_coulter on Sep 08, 2014
  
  Uh, no, steel coils do not fail more often than air bag suspensions in passenger vehicles. Even if you want to cherry pick some rust belt part of the country where coils can eventually rust from heavy salt exposure, replacements are around $100 a spring vs $1,000 for a new air strut. And that's not even considering all the other equipment that air systems require like the compressor, tank, height sensors, etc. It's an apples to oranges comparison, but many heavy rigs use air suspensions because they can better adjust for the weight with such huge variance in loads. They can easily raise and lower themselves. Big rigs also use rely on air brakes, that doesn't mean they're superior to hydraulic braking systems on passenger cars.
  
  Like
- Compaq Deskpro on Sep 08, 2014
  
  Cop car Crown Vics definitely do not have air suspension. They have springs so stiff they have a raised butt stance when the trunk is empty. This is to compensate for hundreds of pounds of radios and gear. Air suspension would never cut it for this application. While the Taurus's springs are indeed junk, you never see coil spring equipped Vics with a sagging butt.
  
  Like
- Relton on Sep 08, 2014
  
  @Compaq Deskpro That's because Crown Vics usually have air springs in the rear. I worked on the cop car programs, and I know for a fact that 98% of the cop car Crown Vics have rear air springs. As do Town Cars & Grand Msrquis. Google Ford Spring recalls for a complete, and extensive, list of Ford steel spring failures. And, some recalls. Tauruses and Windstars had a recall that, instead of fixing the springs prone to break, they simply added a plastic shield so when the spring broke it didn't tear the tire open. It is possible to make steel springs, coil or leaf or torsion bar, with an infinite life. The calculations are easy. What's not so easy is getting management to pay extra for infinite life springs, and spring companies to exercise the manufacturing discipline to make sure they are made properly. And the assembly plant to avoid damaging them during installation. (the source of yet another Ford spring recall) If you're old enough, you may remember when all big rigs had steel springs. Then, some trailers went to plastic springs, and got triple the life of steel springs. Now they all have air springs. If they weren't reliable and durable, none of the big rigs would have them. Same for transit busses. A lot of GE locomotives now have air springs also. If air springs can work for a locomotive, I'm sure they are adequate for a 2 ton cop car.
  
  Like
- Furiouschads on Sep 08, 2014
  
  relton: exactly. i'd like to try out the air ride on my poorly maintained midatlantic asphalt and concrete. thanks for the constructive comments. who knows if i really will do this. if it isn't a rewiring job, it could be an interesting raspberry pi project.
  
  Like
- Sajeev Mehta on Sep 09, 2014
  
  Brilliant, thanks again relton. Glad to hear from you again.
  
  Like
Redman on Sep 19, 2014

The Mark 7 was a fine effort - classic Lincoln styling cues coupled with boy-racer Mustang power. Factory BBS-type wheels also added a great touch. Now the Mark 8, that one hit a whole new high: world class 4-valve per cylinder DOHC V8; computer-driven four-corner air suspension (Caddies of the era were rear air only); and that look - that sharp, razor-edged front end and fighter-cockpit interior the likes of which we haven't seen since. Make mine triple black with a moonroof and chrome Octastar wheels.

Like Reply

Recent Comments

Alan My view is there are good vehicles from most manufacturers that are worth looking at second hand.I can tell you I don't recommend anything from the Chrysler/Jeep/Fiat/etc gene pool. Toyotas are overly expensive second hand for what they offer, but they seem to be reliable enough.I have a friend who swears by secondhand Subarus and so far he seems to not have had too many issue.As Lou stated many utes, pickups and real SUVs (4x4) seem quite good.
28-Cars-Later So is there some kind of undiagnosed disease where every rando thinks their POS is actually valuable?83K miles Ok.new valve cover gasket.Eh, it happens with age. spark plugsOkay, we probably had to be kewl and put in aftermarket iridium plugs, because EVO.new catalytic converterUh, yeah that's bad at 80Kish. Auto tranny failing. From the ad: the SST fails in one of the following ways:Clutch slip has turned into; multiple codes being thrown, shifting a gear or 2 in manual mode (2-3 or 2-4), and limp mode.Codes include: P2733 P2809 P183D P1871Ok that's really bad. So between this and the cat it suggests to me someone jacked up the car real good hooning it, because EVO, and since its not a Toyota it doesn't respond well to hard abuse over time.$20,000, what? Pesos? Zimbabwe Dollars?Try $2,000 USD pal. You're fracked dude, park it in da hood and leave the keys in it.BONUS: Comment in the ad: GLWS but I highly doubt you get any action on this car what so ever at that price with the SST on its way out. That trans can be $10k + to repair.
28-Cars-Later Actually Honda seems to have a brilliant mid to long term strategy which I can sum up in one word: tariffs.-BEV sales wane in the US, however they will sell in Europe (and sales will probably increase in Canada depending on how their government proceeds). -The EU Politburo and Canada concluded a trade treaty in 2017, and as of 2024 99% of all tariffs have been eliminated.-Trump in 2018 threatened a 25% tariff on European imported cars in the US and such rhetoric would likely come again should there be an actual election. -By building in Canada, product can still be sold in the US tariff free though USMCA/NAFTA II but it should allow Honda tariff free access to European markets.-However if the product were built in Marysville it could end up subject to tit-for-tat tariff depending on which junta is running the US in 2025. -Profitability on BEV has already been a variable to put it mildly, but to take on a 25% tariff to all of your product effectively shuts you out of that market.
Lou_BC Actuality a very reasonable question.
Lou_BC Peak rocket esthetic in those taillights (last photo)