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Repairing Koni Front Lifting System in a Diablo

All Lamborghini Diablos (after 1993), the Murciélago and from 2005 onwards Gallardo's have a system that allows the driver to raise the front of the car about 2 inches (when driving at low speeds) to get over obstructions on the road or driveway. Unfortunately this system is a notoriously badly designed system. It is perhaps the greatest failure in the design of Lamborghini cars and is the subject of numerous discussions in Web forum discussion groups. A major problem with this system is that the front Koni shocks (through which oil is pumped into to rise the car) leak. There are particularly prone to do so if they are "bumped" when the car is in the raised condition. The oil pressure system puts out over 1500 PSI to raise the car. The seals in the shocks simply are not designed well to take this pressure.  To make matters worse Koni insists that these shocks are an OEM job and will or cannot repair or replace them. The only current solution is to purchase expensive new shocks from Lamborghini. A number of people have tried to find a solution. The problem is that the shocks themselves are almost impossible to open. The treads are sealed with some kind of "locktight" cement. Some people I know are working on a solution. Nothing yet! 

There is a second problem sometimes seen with the above front lifting system. The symptoms are as follows: When the driver pushes the switch to raise the car, the car rises fine to its maximum height and then immediately drops down again leaving the "raised car" icon light flashing on the dash. Further pressing the switch has no effect unless the car engine is turned off and then back on.  In this situation there are no shock oil leaks, the power steering oil reservoir (see below) is full and the Koni error lamp beside the gear shift is not flashing an error code.  The cause of this problem is tricky to diagnose. To do this it is first necessary to understand how the front lifting system in these cars work.

The Koni Front Lifting System in a Diablo

The front lifting system in Diablos (and the more recent cars) is done by pumping power steering oil under very high pressure into two specialized Koni shock absorbers in the front of the car.  The circuit diagram is shown in the following two diagrams.
Fig 2 Diagram of oil reservoir and Min/Max Switches   Fig 3  Diagram of front air bleed valve connections

As can be seen in the above diagrams the oil for the front rising system is pumped from the power steering reservoir through a valve system to both front shocks. Even tough the same oil reservoir is used by both the front lifting system and the power steering system they behave quite separately. The same pump is used to pressure the oil in both systems however.

The onboard LIE computer carefully monitors the oil pressure put out by the pump required to raise the car. This pressure goes from less than 20 Bar (~260 PSI) to over 100 Bar (~1500 PSI) as the car is raised.  You need this kind of pressure to raise such a heavy car with such small hydraulic pistons (in the shocks). To monitor the pressure there are two pressure sensors, a MIN pressure and MAX pressure sensor switch. These are shown in Figure 4. They are clearly labeled in the steel block they are screwed into. This assembly is located just above the gas tank in the side compartment of the engine area. The Min switch has a adjustable screw painted red. The Max switch screw is painted blue. These screws should normally not be tampered with. They are factory set to set the cutoff pressures for the front hydraulic lifting system and are very sensitive. A slight adjustment of 5 degrees has a big effect see below.

The way the  system works is as follows: The Min switch is a "normally open" switch so when the car is in its (normal) low position, this switch is set open. Removing the two wire connections and measuring the resistance across the switch should show an open connection when the car is in its normal low position. The Max switch on the other hand is a "normally closed" switch. When the car is in the normal (lowered) position removing the two wire connections should show essentially no resistance across the switch contacts.  When the car is raised. The min switch should  close (as the pressure passes above 40 Bar) and remain closed. When the car is full up (and the pressure is over 80 Bar) the Max switch will open.  Both switches should remain in these states while the car is raised. They reverse back to their original states when the car is lowered. 

Both switches have a grey/red wire connector that is connected to ground for both switches. You can check the switches are opening and closing correctly by measuring the voltage of the violet/white lead on the Min switch and the green/black lead of the Max switch during the raising and lowering process.  To see the voltage changes attach a voltmeter clip to the switch contact (at the same time making sure the wire contact supplying the voltage to the switch is not disconnected) and tape the meter to the car window as shown in figures 5 and 6. Then raise the front of the car. For the Min switch the voltage should be +12V  quickly going to 0V and staying there as the car is rising.  For the Max switch on the other hand  the voltage will be 0V  going to +12 volts and staying there once the car is full up.

There are two common ways this front lifting system can fail.

Oil Pressure Failure:  If the power steering pressure pump is not capable of delivering the 1500+ PSI pressure the car can not be raise correctly.  To check this you will need to monitor the oil pressure being sent to the front shocks system.  Fortunately Lamborghini provides a location to tap into the system. It is behind the panel in the front trunk as shown in figures 7 and 8.  This is actually an air bleed screw to get air out of the system during an oil change. To measure the oil pressure we will construct a custom oil pressure gage.

First let me warn you that we are talking about very high oil pressures here. A pipe burst at 1500 PSI will spray oil everywhere and potentially cause bodily injury.  Even when the car is lowered the oil pressure in the system is still ~260 PSI. 

You need to purchase a pressure gage capable of measuring up to ~1500 PSI.  This is well beyond gages commonly used for automatic transmission or diesel engine work. You can get such a gage from for about $25.00. 
Its part number is  #53783 and is made by a company called Valley Instrument.

To attach this gage to the car system you must first relieve the pressure in the system by attaching a hose and container to the air bleed and opening it slowly. See figure 9. When the oil stops flowing remove the air bleed vent. This leaves you with a female fitting.  Fortunately this is exactly the same 0.4" treads that are used in brass tubing fittings found in most (US) hardware stores. You need to setup an assembly as shown in figures 10 and attached it to the car as shown in figure 11.  You have to attach the vertical stem first, then attach the stopcock and gage.  All joints should be Teflon taped and quite tight. This process can be quite messy. It's a good idea to cover the whole area with plastic covering and wrap a rag around the base of the air bleed area to absorb runoff oil.  With the assembly in place (and the stopcock open) start the engine and raise the car. Quickly check for leaks! With the car full up, the oil pressure should go to about 1400 PSI and then fall back to ~1200 PSI (fig 12).  When the car is lowered the pressure drops and stays at about 250 PSI (fig 13).  If you do not see these numbers you may need to replace the power steering pump. 

Now to put things back you need to relive the oil pressure in the system. Close the stopcock and carefully remove just the pressure gage (fig 14). Then put a container under the stopcock and open it. When the oil stops flowing remove the vertical brass tube and put back the Lamborghini air bleed. Tighten it down.  You will also have to add some power steering oil to the reservoir in the back of the car.  If the oil did not come within the above pressure values you either have a failing power steering pump or faulty sensor switches (see below).

As a side note, perhaps the reason these KONI shocks tend to leak is that they always have 250 PSI pressure in them even when the car is in the lowered position. It's not clear to me why this is so. If you vent off the pressure (as described above) the pressure will stay at 0 PSI until the next time the car is raised -- even when the power steering is used. Perhaps the Min oil pressure sensor switch could be adjusted downwards. Some day maybe I will experiment!

Failure of Min Oil Pressure Regulator Switch:  For some reason it is quite common for the Min switch to fail. When it fails the switch contacts stay open always. This will cause the car to rise and  then quickly fall back down.  It is easy to check for this by bypassing the switch as shown in Figure 15. The car should then raise correctly and stay up. (The icon on the dash indication the car is raised will stay flashing -- indicating an error however). Nevertheless you can raise and lower the car with no problem.  Note the Max switch could fail too. Check the voltage readings as described above to be sure.

To replace the Min switch you must release the oil pressure with the oil/air bleed system as described above. You them need to drain the power steering fluid reservoir. I find the easiest way to do this is to siphon it out using a brake fluid vacuum pump to get things started. To be on the safe side you should surround the Min/Max switch block area with some rags (fig 16). You don't want oil dripping on top of the gas tank area below.  Now we are ready to remove the Min switch.  Remove the connecting wires and with a 25mm socket carefully screw out the assembly see fig 17 & 18 (Note in fig 17 rags were removed for photograph). Be real careful not to loose the brass/rubber gasket (fig19).  Transfer this gasket to the new unit and screw the new unit back in. The Lamborghini part number for this switch is  #51009370 (It costs ~$245*).  Reconnect the wires. Fill the power steering oil reservoir to within 1 inch of the top. Do not overfill this reservoir. If you do it will overflow through a small bleed hole (figures 20 & 21) in the rubber top knob and drip down on to the compartment below.

You are now ready to test the lifting system. The first time you start the system up, it seem to take a little longer to raise the car. This is because the pump is building the pressure up from 0 PSI to the normal base 250 PSI. The car starts to rise from then on. This can be easily seen if you use the oil pressure gage setup I described above.   It may be necessary to bleed air out of the system -- though I have not found this to be so -- using the oil/air bleed nozzle I described above.


* The Lamborghini "Pressure Regulator - Min" costs $250.00.  Interestingly what looks like the exact same switch sold by PLV Ltd in England costs 25 Euros.  See - PMN.pdf. Lamborghini parts pricing again!


Fig 4. Min & Max pressure switches Fig. 5. Testing Max pressure switch Fig 6. Attach voltmeter to door window
Fig 7. Oil bleed nipple Fig 8.   Close-up of oil bleed nipple

Fig 9. Relieve oil pressure

Fig 10.  Custom Fitting to measure oil pressure


Fig 11. Custom fitting in place Fig 12. Car raised. 1100 PSI
Fig 13. Car lowered 250 PSI


Fig 14. Remove gage. Release pressure Fig 15. Short Min switch leads
Fig 16. Surround switch block with rag


Fig 17.   Remove Min pressure switch Fig 18.  Min switch removed
Fig 19.   Min pressure switch and gasket


Fig 20.   Air bleed hole on steering fluid reservoir Fig 21.   Air bleed hole on steering fluid reservoir


This page was last modified on 03/12/2014

This page was last modified on 09/06/2014