2003 STS suspension conversion
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2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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22,639 Posts
Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!
My son has an '03 STS with the F45 struts
can't be -
the 2003 STS has the F55 - MagnaRide suspension system -
or whatever the Corvette (?) option was
there were no optional suspension systems -
ALL 2003 STS models came with the F55 system -
we tried different conversions 10 years ago and nothing worked
all you need is the non-electronic struts and shocks that are used on the SLS model -
and install a set of resistors to satisfy the suspension computer -
He drives it low and slow
not sure what this means -
if the rear end is sagging - there is a problem with the ELC - Electronic Level Control system -
Can engine/trans control units be swapped out to in essence remove the F45 option?
the PCM - Power Control Module that controls the engine and trans has nothing to do with the suspension system -
as I stated above -
a simple set of resistors is all you need to trick the suspension computer
into believing the F55 struts and shocks are there and working -
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My son has an '03 STS with the F45 struts
can't be -
the 2003 STS has the F55 - MagnaRide suspension system -
or whatever the Corvette (?) option was
there were no optional suspension systems -
ALL 2003 STS models came with the F55 system -
we tried different conversions 10 years ago and nothing worked
all you need is the non-electronic struts and shocks that are used on the SLS model -
and install a set of resistors to satisfy the suspension computer -
He drives it low and slow
not sure what this means -
if the rear end is sagging - there is a problem with the ELC - Electronic Level Control system -
Can engine/trans control units be swapped out to in essence remove the F45 option?
the PCM - Power Control Module that controls the engine and trans has nothing to do with the suspension system -
as I stated above -
a simple set of resistors is all you need to trick the suspension computer
into believing the F55 struts and shocks are there and working -
Welcome to CF !!! Your question on STS suspension work has been moved to its own thread. Please do not hijack threads - start your own thread on your own problem. Thanks.
Please update your profile to show car(s) driven, approximate location, time zone, etc.. It sure helps with advice and diagnosis.
All 2003 STS had active MRC; SLS had passive suspension. The late 2002 and all 2003 STS were the field test mules for the MRC system before it went into other GM/Cadillac models. The last (2004 model year) Seville was built in December 2003.
Yes, the car has the Lord/DELPHI F55 Magnetic Ride Control suspension (has nothing to do with the later Corvette suspensions or options) - look at the code on the RPO sticker under the spare tire cover. RPO = Regular Production Option - what's built into THAT car.
AC Delco 580120/0121 struts - https://www.rockauto.com/en/catalog/cadillac,2003,seville,4.6l+v8,1411872,suspension,strut,7584
basscatt has all the particulars on how to convert the car to passive soft ride struts, shocks, and springs. Some hoops to jump through.
All these cars had ELC - Electronic Level Control - on the rear shocks. It's NOT "air ride" - it's a compressor/air bladder system that compensates for extra weight in the trunk or rear seat. It is an independent system and is not suspension control. The front struts do not have level control bladders.
We tried the "resistor solution" ten tears ago and it was a waste of time, money and effort. He found a shop with a Tech 2 and it worked for 2-3 weeks and then reverted to the original status.
He loves the car, still drives it (144K) so...we'll try again.
He loves the car, still drives it (144K) so...we'll try again.
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
22,639 Posts
===============================
We tried the "resistor solution" ten tears ago and it was a waste of time, money and effort.
the CORRECT resistor solution worked 10 years ago - and still works today - when properly applied -
the resistors are used when passive - non-electronic - struts and shocks are used to replace the active F55 units -
all it does is creates an electrical load - to simulate the electrical load of the original F55 struts and shocks -
it tricks the suspension computer into believing that the F55 struts and shocks are still installed - and working -
-----------------------
this solution has been recommended here for MANY years -
and MANY members have used it successfully -
He loves the car, still drives it (144K) so...we'll try again.
if you are going to keep the car for a long time - NOW is the time to do it the RIGHT way -
as stated earlier - the coil springs on the F55 Seville are really soft - I recommend replacing them with the SLS springs -
for struts I recommend the MONROE 171684 Quick Strut - $240 - for the pair - including shipping -
rockauto.com
this is a complete - fully assembled strut assembly with all brand new components -
strut - spring - spring seats - bearing - mount - bellows - etc -
for the rear -
SHOCKS -
MONROE MA822 - $56.79 - for the pair - with free shipping -
https://www.amazon.com/gp/product/B000C55T7W/?ie=UTF8&me=ATVPDKIKX0DER
SPRINGS -
MOOG 80659 - $59.79 - for the pair - with free shipping -
https://www.amazon.com/gp/product/B000V53PHE/?ie=UTF8&me=ATVPDKIKX0DER
almost forgot -
RESISTORS - 2 ohm 10 watt resistor - you need 4 - 1 for each strut/shock -
here is a 10-pack - $2.95 - with free shipping -
https://www.ebay.com/p/10-Pcs-Wire-...-10w-Watt-T9n7-Bk/1069567059?iid=254074859245
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so - for around $350 worth of parts - you can have a really nice riding STS -
it's always fun when someone comes here for advice, doesn't like the advice, says the advice didn't work, so of course it was a waste of time. Roger97, two of the most knowledgeable people on the planet are giving you advice. Sub and Bass are trying to help. Suggest you take their advice. Regarding post #4, if someone with a true Tech2 made a change it doesn't magically change back two weeks later.
??? "resistor solution" ??? It's not a solution - it's the only way to fool the stability and body control systems when you delete the active F55 struts and shocks and simultaneously install passive units. The correct resistors simulate the electrical load of the active strut/shock - ~2 Ohm 10 Watt for F55 MRC; 4700 Ohm 1/2 Watt for the earlier F45 CVRSS systems. Different electrical loads = different resistor requirements.
The F45 and F55 body control systems receive inputs from over a dozen sensors and conditions - including roll, pitch, yaw, power level, vehicle speed, wheel speeds, braking action, steering wheel position, desired turn radius, actual turn radius, gear position, sideways acceleration, others. You need to either maintain the system to OEM high performance standards or fool it to get to a decent passive suspension level.
It's a far, far more sophisticated performance car than many people think, so you can't just throw BandAids at it and have one or two stick. Either restore it to OEM specs - or do the passive suspension conversion correctly, as per basscatt - or don't even try.
FWIW, The F55 MRC system uses a hydraulic fluid that has many millions of iron spheres suspended in it. The fluid transfer port through the piston contains a magnetic (solenoid) coil. The magnetic field around the port is varied as a function of body control signals - the fluid in the port area actually goes from 5W oil to thick jelly and back in less than .001 second, so it offers great damping control over strut/shock piston (suspension) movement.
The older F45 system uses differing port sizes to control oil flow inside the strut/shock.
Passive units are fixed flow - one damping setting and that's IT.
Roger, Just as an aside - when you first posted this in an Eldorado thread concerning F45 suspensions - The Eldorado, slated for extinction in 2002, never got any upgrades past 1999 except for the engine/transmission. So Eldorado (ETC) and Deville (DTS) never had the later F55 MRC suspension. Only the 2002.5 - 2003 - 2004 STS - Seville Touring Sedan, had it - and the only 2004 STS (274 built until December 2003) were all exported to Canada/Europe. (The 2006 and later "DTS" is NOT a Deville.)
The F45 and F55 body control systems receive inputs from over a dozen sensors and conditions - including roll, pitch, yaw, power level, vehicle speed, wheel speeds, braking action, steering wheel position, desired turn radius, actual turn radius, gear position, sideways acceleration, others. You need to either maintain the system to OEM high performance standards or fool it to get to a decent passive suspension level.
It's a far, far more sophisticated performance car than many people think, so you can't just throw BandAids at it and have one or two stick. Either restore it to OEM specs - or do the passive suspension conversion correctly, as per basscatt - or don't even try.
FWIW, The F55 MRC system uses a hydraulic fluid that has many millions of iron spheres suspended in it. The fluid transfer port through the piston contains a magnetic (solenoid) coil. The magnetic field around the port is varied as a function of body control signals - the fluid in the port area actually goes from 5W oil to thick jelly and back in less than .001 second, so it offers great damping control over strut/shock piston (suspension) movement.
The older F45 system uses differing port sizes to control oil flow inside the strut/shock.
Passive units are fixed flow - one damping setting and that's IT.
Roger, Just as an aside - when you first posted this in an Eldorado thread concerning F45 suspensions - The Eldorado, slated for extinction in 2002, never got any upgrades past 1999 except for the engine/transmission. So Eldorado (ETC) and Deville (DTS) never had the later F55 MRC suspension. Only the 2002.5 - 2003 - 2004 STS - Seville Touring Sedan, had it - and the only 2004 STS (274 built until December 2003) were all exported to Canada/Europe. (The 2006 and later "DTS" is NOT a Deville.)
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