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Buick Riviera 1991 and the 1993 Suspensions different ride


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Hi folks!<BR>I have a 1991 Riviera with the self levelling suspension in the rear, and the car rides soft and very comfortable,the tire size is 205x70x15 however lately the suspension is gone much softer at the back and the front probably needs new struts, as the '91 Riv has just under 150K miles.<BR>The rear height increases when more load is in the trunk.<BR>My 1993 has a tire size of 215x60x16 Michelin X-one , and the suspension is much harder/stiffer, the rear doesn't seem to be working , I see the rear struts are air, i.e it has the height sensor and the pump ass'y , however it does not glide like the 1991 Riv, can someone tell me what if anything to check on these cars for this kind of problems?<BR>I read somewhere , that the 1993 Riv's came with the Road Sensing suspension(rss) very similar setup to the rear I suspect, however I am not sure, as to it's operation /troubleshooting.<BR>Also where can I buy the parts for this kind of suspension, i.e the pump, motor, the height corrector, do I always have to go to the GM for the parts.<BR>many thanks for any help on this matter.<P>prakash

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I highly suspect that if the later model Riv rides firmer than the earlier one, it would be due to different suspension calibrations and different suspension codes (i.e., FE1 for the base suspension and FE2 or FE3 for the firmer one). You can find those codes on the Service Parts Identification Label that usually is on the top of the spare tire cover. <P>I do not recall any Rivieras having electronic struts and "road sensing" as the Cadillacs did or do. What Monroe calls "road sensing" in their shocks/struts is NOT the same thing as electronic struts as Cadillac and Corvette uses that are controlled by the body module computer from wheel sensor inputs or calibration mode switches. <P>By that point in time, if any suspension upgrades were done, it was not with the struts but with stiffer springs, larger sway bars, and performance oriented tires (with stiffer treads and sidewalls). When you add in the performance nature of the 16" tire package you have, "float" will be decreased as less movement is filtered out by the performance-oriented tires. I would suspect that if the later Riv is supercharged and the earlier one is not (as the smaller 15" tire size would tend to indicate), that could be the reason for the suspension being calibrated differently.<P>When the automatic leveling kicks in, it should only raise the vehicle to the original ride height, not higher. There is a height sensor in the rear suspension to control that issue. In any event, in it's "curb ride height" with no one in the car, the rocker panel should be basically level, but many newer vehicles are configured such that the rear is slightly higher than the front when unloaded. I seem to remember those Rivs being a little higher in the rear when empty.<P>I seem to remember that the earlier version of those Rivieras could be had with a "base" car (i.e., base 3800 V-6 of about 200 horsepower, normal 15" wheels and tires, softer springs and sway bars) or with the optional supercharged 3800 and appropriate suspension upgrades (all with automatic leveling). In the later years, it seems the supercharged 3800 became standard and would probably have also included the suspension upgrades as standard too. They all sat higher in the back such that the rocker panel tilted upward toward the rear end of the car.<P>As far as I know, all of the pieces of the automatic leveling suspension are going to be dealer only items. The rear struts can be obtained from aftermarket sources, though, just as shock absorbers would, but will need to have the correct fittings for the factory air lines on them. If the automatic leveling is not desired, you can unplug the compressor for the system. But, it sounds like the system is operating as it should and just needs a check of the height sensor at the back.<P>Just some thoughts . . .<P>NTX5467

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Hi,<BR> thankyou for the information.<BR>as far as I know, the 1989 came with this shape, with the exception that the interior and the dashboard was different in that it has a touch screen in the centre console, and that the engine is only a 165HP again a 3800 V6, then the 1990 also the same exterior shape,and the same engine as the 1989-with the 165HP 3800 V6,with the only change in the dashboard and the interior.<BR>However the 1991-1993 has the same engines , i.e the 3800 V6 with 170 HP engines, the only difference the brake rotors were slightly bigger from the 1992 to the 1993, and that most 1993's came with the 16 inch Alluminium wheels.<BR>As far as I know they were not supercharged engines, and that there was no production of the Riveira's in 1994, however the only time the supercharged engines were introduced in these Riviera's were 1995 which came with the first generation of these 3800 V6 Supercharged engines and produced 225HP, then from 1996 these Riveira's came with the second series Superchargers with 240HP until 1999 when the production ceased.<BR>All these cars came with the self levelling suspensions at the rear, however the Chilton's Service manual says that some of the late model i.e the 1993's came with the RSS at the front-as it mentions to remove the wiring harness/ air tubing before removing the front struts-this is where I got confused.<BR>I once had a 1992 Oldsmobile Toronado Trofeo same powertrain and the suspension setup as the 1993 Riviera , and I recall the suspension in that car was stiff, however it made one feel , one is afloat.<BR>I am certain that my 1993 has problem either with the sensor/compressor and or may have an air leak. I would have to troubleshoot further.<BR>many thanks again<P>prakash

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When I made the post last night, I was thinking that your vehicles were the next and last generation of Rivieras, hence the reference to superchargers.<P>I did check the GM parts database and discovered that all of the rear struts for the 91-93 Rivs are the same. The fronts for the 90-91 Rivs are the same, but the 93 uses a right and left strut instead. The upper strut mounts on the front are the same part, but there must be some bracket or something attached to the struts that makes them side specific in the later years. There was only one part number for the front struts--no "RSS" option listed, but I didn't check the 94s.<P>In order to track that situation, it would be necessary to find some factory literature to confirm it. GM has ceased to support the electronic struts on the Allantes and issued a service bulletin of how to retrofit the non-electronic struts and keep the computer from knowing what was happening. If there was such an option on the Rivs, it would have probably received a similar fate, but I don't recall the bulletin applying to anything other than the Cadillac Allante/Eldorado vehicles. In any event, if your car had that, there would be some wires going directly into the strut itself plus a small lever going between a motion sensor at each wheel and the lower control arm.<P>There were standard suspensions and upgrade suspensions. The difference between them is the springs and sway bars as the struts are common items between them.<P>If done correctly, the firmer suspension calibration will be firm but not harsh. On rough roads the car will be more stable and feel like it is "above it all", so to speak, but without really floating or feeling mushy as the softer suspensions might be.<P>I also checked the price on the rear suspension height sensor -- $369.00 retail. A good troubleshooting session might be in order. I suspect the more specific GM factory service manual might be better than the Chilton in many situations. The Chilton, Clymer, and Motor manuals are good, but are more generalized in nature and could miss some year specific items in the process, especially in illustrations. <P>Enjoy!<BR>NTX5467

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hello and thankyou for the information.<BR>You are right, I will use the Buick OEM service manuals as I now have them.<BR>I forgot to mention that the 1991 Riv has on the dashboard which says: Dynaride suspension, and the latter the 1993 says: Grand Touring suspension.<BR>I will be troubleshooting , and will post my replies.<BR>many thanks <BR>prakash

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well, after shopping at the Costco, the trunk was filled with all the shopping, including 10 litres of bottled water and more, just enough to let the automatic air compressor to come 'on' and let the car be pumped up to maintain it's rear height. Well the pump came 'on' as I could hear the pistonic sound coming from the rear end,however the car's rear end remained in the same position , i.e loaded and the trim height was just below the top of the rear tire. I am not sure , but certainly it tells me that the sensor is doing the job in that it is allowing the pump to come 'on', however I would have to disconnect the air line connection that comes out from the pump which goes into the 'T', and perhaps place a gauge that reads the PSI, ( I read it somewhere that once the car has a certain load the aircompressor comes 'on ' to maintain the rear height so that it is one inch above the top of the rear tire, and the compressor will produce if needed up to 67 PSI with the full load, though when there is no load , the automatic height is maintained the same level = one inch above the top of the rear wheel, and the rear struts receives approx 10-17 PSI to give a better ride, like being afloat.<BR>I will write some more once I find out more.<BR>prakash

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"DynaRide" is a Buick tradename for their suspension calibration in the earlier 1990s. It was a comprehensive "system", as they claimed, that began with the suspension and ended with the seat cushions, with the end result being a smooooother and more comfortable ride. The key item in the suspension was struts with "deflected disc" valving instead of the more common spring loaded popoff valves. That's what I recall the literature of the time mentioning.<P>On those same vehicles (DynaRide), if you ordered the suspension upgrade option, it wasn't DynaRide any more. That was the "Grand Touring Suspension" option (with the appropriate instrument panel nameplate). As I mentioned, the Grand Touring Suspension was slightly stiffer springs, larger sway bars, more performance oriented tires, particular aluminum wheels, and the same part number struts as the normal suspension.<P>The rear air struts need a minimum air pressure to keep their rubber diaphrams inflated sufficiently to not damage them during suspension movement. The 67psi sounds a little low compared to the 90-120psi that previous air shocks would tolerate for their max loads, but the aftermarket air shocks would allegedly allow up to 1000lbs to be added to the vehicle's rear suspension and still maintain correct ride height. <P>If the compressor's running in the loaded condition, it sounds like the system is still operating as designed and it could be a hole in the air line or the more possible issue of an air strut with a hole in the diaphram. <P>A good troubleshooting with the car on an overhead lift might be in order. Probably just a good check of the lines looking for leaks might be the best orientation without getting the air pressure gauge involved except as a last resort to check the pump.<P>Thanks for the additional information.<P>Seems like the similar rear air struts (from GM) for a DeVille are about $235.00 each plus labor. Any aftermarket (i.e., Monroe) struts for that car would need to have air fitting compatible with your factory fittings in order to maintain the automatic level control system. Or, the less expensive alternative would be to pull the fuse of the compressor, as many tend to do.<P>Enjoy!<BR>NTX5467

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Hi,<BR> thankyou for enlightening me with regards to the Dynaride and the Grand Touring suspension.<BR>I had purchased a set of Monroe Struts for my 1991 Riv, the rear ones are the same as the OEM, in that it has the exact air fitting , and the front ones have no air inlets. <BR>I am used to a more softer ride, as I drive a 1986 Citroen CX with the Hrdro-pneumatic suspension which is the same system the Rolls Royce company has adopted for may years.<BR>The 1993 Riv which has the hard ride , I was just checking the fuses, and found one that was missing and that was a 20 Amp fuse that was controlling the Compressor as well as was a common fose with the Cigar Lighter, henceforth what you had mentioned above is correct, someone was cheap and took the fuse out, I on the other hand am glad that I can troubleshoot and rectify the system, I will try and order in the air line kit as they call it,also will check if the compressor is actually functioning as far as producing the air.<BR>I was quite disappointed after being at the Buick Dealership, that they only sell the whole pump as a complete ass'y, and that they do not sell components individually that would be needed for repairing the compressor unit. Although I have a parts book for the 1986-1993 Riviera which shows with an exploded view as well as what the pieces are called, and it clearly states that the parts are available for repairing the compressor if need be.<BR>I plan to get my 1993 Riv's suspension done right, and would like the feeling of being afloat.<BR>prakash

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Hello, <BR>I have now checked the rear suspension, there are no leaks, the sensor works the compressor pump, when the car has the load, however there is no air , I placed a PSI gauge that should have read something, nothing,at all. I tested the rear Shocks if there was any leaks by pumping it with an external compressor, and they are good with no leaks.<BR>I now have to remove the whole pump with from the rear Right, I am not sure how I would go about removing it from the car, as it doesn't give me much room to work with.<BR>Does anyone have any ideas , as I can repair it should the necessary parts be available, the pump works, but no air output, the air filter is ok, as I had disconnected it from the fitting, still no output, I suspect the pump may not be compressing any air, though I don't really know how such a setup works, I have figured it's workings as a system , however the unit on it's own , once it is out of the car I can figure it out very quickily.<P>prakash

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