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LDS cap leaking fluid through the tiny hole in cap : is it Defective ? |
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citroenroen1
 
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  Member No: #5495
Location: Los Angeles |
Do I have a defective LDS reservoir cap ? What are symptoms of a BAD / Defective LDS (pressure) cap ? Since I replaced my right front Suspension hydraulic unit, I meticulously cleaned everywhere under the hood in the vicinity of the LDS reservoir, coolant reservoir and in the wheel arch area (inner fenders are removed at this time) : I noticed there were signs of leaked oil / fluid everywhere : I attributed the leaked fluid to the tired suspension unit and perhaps a previous leaking drive axle boot. When the C6 motor is running (and when I raise and lower suspension) , I notice LDS fluid seeping through the tiny hole in the LDS reservoir CAP ? After a while , there is fluid leaking down onto high pressure pump feed hose and eventually onto my new Main Sphere. Is the seeping LDS reservoir cap a symptom of a defective LDS cap or a symptom of something else ? |
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C6Dave
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   Member No: #1
Location: Northumberland |
Have you overfilled the system with LDS? | ||
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citroenroen1
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Member No: #5495
Location: Los Angeles |
I have not overfilled the LDS reservoir . I failed to mention that I have followed correct procedures for checking fluid LDS fluid level . When I remove cap in normal position , there is no fluid visible in LDS container. WHen I remove cap in low position, there is a little fluid visible in bottom of LDS reservoir as it should be . What are the symptoms for a defective LDS reservoir (pressure) cap? |
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C6Dave
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Member No: #1
Location: Northumberland |
citroenroen1 wrote ... What are the symptoms for a defective LDS reservoir (pressure) cap? This may help you: - Click Here -, and%20requiring%20a%20complete%20disassemble%20to%20clean. From a C5 but it's basically the same system If you Google it there is a long 'AI' answer AI Overview A failed or damaged LDS reservoir cap, particularly on Citroen vehicles with hydraulic suspension, can cause several problems including fluid loss, potential overfilling of the reservoir, and even pump damage. It's crucial to ensure the cap seals properly to prevent leakage and maintain the system's pressure. Here's a more detailed explanation: Fluid Leakage: A faulty cap can lead to fluid loss, potentially affecting both the suspension and power steering systems, as they share the same fluid supply. Overfilling: If the cap doesn't seal properly, it can allow excess fluid to enter the reservoir, potentially leading to overflow and spills. Pump Issues: Overfilling or a leaky cap can cause LDS fluid to spill onto the pump housing and potentially enter the pump's electrical components, leading to overheating and damage. Pressure Issues: A bad cap can prevent the system from maintaining proper pressure, affecting the suspension's functionality and potentially causing it to fail to rise or lower correctly. Height Sensor Issues: In some cases, a faulty cap or overfilling can also cause height sensor malfunctions, preventing the suspension from recognizing the vehicle's position. What to do if you suspect a failed cap: Check the cap: Inspect the cap for damage, cracks, or a poor seal. Examine the reservoir: Look for signs of leaks around the cap or on the reservoir itself. Check the fluid level: Ensure the fluid level is within the specified range when the car is on a level surface and the suspension is at its lowest setting. Consider replacing the cap: If you suspect the cap is faulty, replacing it is a good first step. Consult a professional: If you have concerns about the LDS system or the fluid level, it's best to consult a qualified mechanic, especially one familiar with Citroen hydraulic suspension |
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Tjensen
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 Member No: #954
Location: Bergen |
There are several versions of the cap. The latest (and safest) have small hole that will leak oil in a "overfill" situation. The alternative may be a blown tank (pressure). Earlier caps would not let pressure out and a destroyed tank may be the result. It is difficult to be sure of correct level and overfill is quite usual (several times done be me and by my garage) | ||
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citroenroen1
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Member No: #5495
Location: Los Angeles |
Tjensen: thank you for your reply : Please tell me the correct part# for the "latest (and safest) version" of the LDS Reservoir cap so I may order one C6 Dave: thank you for your reply : Is the C6 Hydraulic system pressurized? Is the LDS cap therefore a pressure cap or simply a vented cap ? I will replace the cap as soon as I know the correct part# to order. How many different versions of the LDS Reservoir Cap are there ? What are the differences / improvements in the LDS reservoir caps? Why was it changed? I do not see anything obviously wrong with my LDS Reservoir cap that I can tell. I will plan to replace it none the less . LDS Reservoir level was correct this morning in low position. I have thoroughly cleaned all around the LDS Reservoir : all appears fine and "dry" after cleaning. |
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C6Dave
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Member No: #1
Location: Northumberland |
citroenroen1 wrote ... How many different versions of the LDS Reservoir Cap are there ? What are the differences / improvements in the LDS reservoir caps? Why was it changed? Looks like 3 versions for all models, but no idea why they changed I'm afraid. I can only assume that the latest part number is: 4009 V9 HYDRAULIC RESERVOIR CAP dated 27/02/2012 as production ended in 2012. |
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Tjensen
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Member No: #954
Location: Bergen |
C6 Dave has the right part number. I guess they first wanted to have a sealed system (LDS hygroscopic fluid) and then experienced that it invited problems with blown tank under some circumstances. The latest introduces a little hole that reduces the problem. The leakage you experience is possibly a good thing..... | ||
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citroenroen1
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Member No: #5495
Location: Los Angeles |
Thanks for part # 4009 V9 : I ordered it . Tjensen: My C6 LDS reservoir cap has the "little hole " where the LDS fluid has been leaking out from . Apparently the 4009 V9 cap has this as well ? Is the C6 LDS reservoir pressurized ? |
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MGmike
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  Member No: #3151
Location: South Queensferry |
okay.. lets think about this scientifically and go back to school! If you put the suspension in the lowest setting, fill the fluid to the correct level and put the unvented cap on... you now have a system that's sealed at atmospheric pressure. If you select high and the pump draws the fluid from the tank to fill the struts, the tank must be in a vacuum as the original unvented cap doesn't allow air in to the system. This is not good for the pump.... If you now select low and the fluid returns to the tank, the tank will return to atmos pressure. Change the cap for a vented one and the system remains at atmos throughout the range of low to high. This is great for the pump but not so good if you need to overcome an air lock when a component has been replaced (it's commonly accepted 0.5bar is required to ensure the fluid gets to the pump when the system has been depressurised). So, the third iteration of the cap may well accommodate these lessons learned and have a "check valve" that allows air in but only allows air (or fluid if overfilled) out when a pre-set pressure has been reached (circa 0.5 Bar). This is only speculation on my part as I've never tested any of this theory... but it works in my head, especially on a wine Wednesday  
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citroenroen1
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Member No: #5495
Location: Los Angeles |
Thank you for your post MGmike: DO you believe that the original CAP 4009.L6 (first iteration) is unvented ? And then is the Newest CAP 4009.V9 (third iteration) vented via check valve ? (what was the 2nd iteration design of the CAP ? ) Would my recent experiences with LDS fluid leaking out through my CAP 4009.L6 "weep hole" indicate a faulty cap or an over pressurization of the LDS reservoir? In past experiences with D model, when lowest suspension height is selected , I hear air coming out of LHM reservoir CAP weep/ vent hole . CX Reservoir Cap is vented. Is C6 reservoir CAP different design necessitated by the need for pressurization? |
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C6Dave
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Member No: #1
Location: Northumberland |
citroenroen1 wrote ... DO you believe that the original CAP 4009.L6 (first iteration) is unvented ? And then is the Newest CAP 4009.V9 (third iteration) vented via check valve ? (what was the 2nd iteration design of the CAP ? From an online parts manual: 4009.L6 was the cap listed from inception until RPO 120029 (26/06/2005) then the same cap is listed from OPR 12030 (16/10/2009) Until OPR 12151 and was replaced from RPO 12152 (15/02/2010) with 4009 V9 As no one on site actually works for Citroën, we are not privy to the reasons why actual design changes were made. Your only recourse for that is to contact Citroën direct for that degree of technical support. RPO is the same as ORGA Number  |
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MGmike
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Member No: #3151
Location: South Queensferry |
As Dave said, some of your questions can only be answered by the Citroen design engineers and any answers I give here are either supposition or gained from limited experience of owning/fixing these cars. Therefore please accept these answers as being my opinion and may not be factually correct but here goes..... citroenroen1 wrote ... DO you believe that the original CAP 4009.L6 (first iteration) is unvented ? Yes. However I have no experience to support this. citroenroen1 wrote ... And then is the Newest CAP 4009.V9 (third iteration) vented via check valve ? This is supposition on my part and, as I said, I have not verified this as fact. citroenroen1 wrote ... (what was the 2nd iteration design of the CAP ? ) I don't know as I've not seen any data as to the design change. citroenroen1 wrote ... Would my recent experiences with LDS fluid leaking out through my CAP 4009.L6 "weep hole" indicate a faulty cap or an over pressurization of the LDS reservoir? If you have a "weep hole" it isn't a 4009.L6 as those early caps IFAIK do not have a weep hole. However, any loss of fluid through a weep hole would, in my opinion, indicate the system is over filled. citroenroen1 wrote ... Is C6 reservoir CAP different design necessitated by the need for pressurization? Again, one for the Citroen engineers as I have no design data to confirm if the system is pressurised in normal operation. |
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citroenroen1
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Member No: #5495
Location: Los Angeles |
Further conversations / observations of C6 LDS reservoir CAP: My new cap 4009 V9 arrived and it is in fact a VENTED CAP : vented through the tiny hole on top of the cap, like my previous cap . To verify this, I have blown air through the new cap from both directions and observed the same stream of air. The only difference is the plastic extension on the inside of the cap with a small 3mm hole halfway up the top of the extension . WHAT CAN be the purpose of the 3mm hole in this extension in the new 4009 V9 LDS CAP? If I had a blown / bad sphere, wouldn't that cause the aerated fluid to expand and squeeze its way through and out of the tiny vent hole ( and make a mess) regardless of which version of CAP your C6 has ? |
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Tjensen
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Member No: #954
Location: Bergen |
I have experience with two types. In my 2010 model I had the 4009 v9. It will allow leaking if overfilled. Happened many times, even when I was sure the level was correct. Never any pressure when I open it. But then (2024) I lost the cap and got a new one from an older C5. It allows pressure to build up and there is a hiss when opened. Possibly this one will allow the tank to be destroyed if there is high pressure/vacuum in the system. Probably I will look for a new "4009v9". |
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