Don Del Posted May 10, 2023 Share Posted May 10, 2023 I run a 1999 Defender 110 V8 Station Wagon which is a factory build. About 4,000 miles ago the level of the fluid in the clutch master cylinder started to start falling at a noticeable rate. Thinking that the fault was probably in the hydraulic system I subsequently changed out both the master cylinder and the slave cylinder with TRW and AP units respectively. I also replaced the section of flexible hose. On inspection of the old parts no evidence of any leakage was found. Recently the problem has become worse with the level of the master cylinder completely falling after about 200 miles. Today I checked out the system again without finding anything wrong. This leads me to the conclusion that there must be a problem with the clutch itself. Before I take the next step any observations or suggestions would be welcome. Also any suggestions regarding brands of replacement clutch parts would be appreciated. Cheers, Del Quote Link to comment Share on other sites More sharing options...
steve b Posted May 10, 2023 Share Posted May 10, 2023 Does the pedal action change during the fluid level drop? Are you using DOT4 fluid? No fluid showing at the bellhousing drain? Steve Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 10, 2023 Author Share Posted May 10, 2023 13 minutes ago, steve b said: Does the pedal action change during the fluid level drop? Are you using DOT4 fluid? No fluid showing at the bellhousing drain? Steve The operation of the clutch is perfectly normal at all times with nothing to suggest any problems at all. The point at which the clutch engages/disengages hasn´t altered and there is no sign of any slip. Del Quote Link to comment Share on other sites More sharing options...
smallfry Posted May 10, 2023 Share Posted May 10, 2023 Firstly, I do not think you will get any better than TRW or AP cylinders. To be clear, the fluid disappears from the master cyl, and you top it up. Empties again, and you top it up again, and repeat, and repeat ? No signs of leakage underneath or down the clutch pedal ? Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 10, 2023 Author Share Posted May 10, 2023 41 minutes ago, smallfry said: Firstly, I do not think you will get any better than TRW or AP cylinders. To be clear, the fluid disappears from the master cyl, and you top it up. Empties again, and you top it up again, and repeat, and repeat ? No signs of leakage underneath or down the clutch pedal ? No signs of leakage anywhere. All of the fluid that has been added can only be resulting in the piston in the slave cylinder being pushed further along it. There is no sign of any air in the system and it has been bled on a number of occasions. As I mentioned previously the operation of the clutch is perfectly normal. All I can think of now is that there is a problem with the thrust race lever assembly that is requiring the slave cylinder piston to travel further forward. Del Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 11, 2023 Share Posted May 11, 2023 Can you get a cheap boroscope (USB ones are $10 on eBay these days) and have a look inside the bellhousing to see what's going on? Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 11, 2023 Author Share Posted May 11, 2023 3 hours ago, FridgeFreezer said: Can you get a cheap boroscope (USB ones are $10 on eBay these days) and have a look inside the bellhousing to see what's going on? That is a good idea. I have been thinking about getting one for some time. The only issue is that it will cost another $50-$60 to get it here with courier charges and import duties and a couple of weeks in transit. As it stands I have resigned myself to ripping out the gearbox to find out what is going on because something is definitely not right and it is the only way of rectifying any problem. Cheers, Del Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 11, 2023 Share Posted May 11, 2023 2 hours ago, Don Del said: As it stands I have resigned myself to ripping out the gearbox to find out what is going on because something is definitely not right and it is the only way of rectifying any problem. That's a bit extreme - you can pull the slave cylinder and peer through the hole rather than rip the whole lot out. I drilled a 1/4BSP breather hole in the top of my bellhousing, that also lets me look down right on top of the release bearing & clutch. 1 Quote Link to comment Share on other sites More sharing options...
smallfry Posted May 11, 2023 Share Posted May 11, 2023 If there are no visible leaks, and you keep refilling, I cant understand where it might be going. Quote Link to comment Share on other sites More sharing options...
steve b Posted May 11, 2023 Share Posted May 11, 2023 Also, the slave cylinder is only so big....one or two refills of the reservoir would take the piston to the end of the travel ( they do have a circlip?) or out of the cylinder. Does it only lose fluid with use or will it drop when still for a period? This is a head scratcher for sure, but I would want to eliminate everything else before splitting the engine and box. Steve 1 Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 11, 2023 Share Posted May 11, 2023 2 hours ago, smallfry said: If there are no visible leaks, and you keep refilling, I cant understand where it might be going. No visible leaks is the key here - it could be weeping at a joint that's also oily, or something bizarre like a pinhole in the rubber pipe that only squirts a little bit out under pressure which then burns off on the exhaust. I'd be cleaning up every joint and flexi with brake cleaner until it's clean and bone dry and then keeping a very close eye on it. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 11, 2023 Share Posted May 11, 2023 If you'd all just see the light and fit an auto, there'd be no more of this sort of nonsense on here.... 1 1 Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 11, 2023 Author Share Posted May 11, 2023 4 hours ago, FridgeFreezer said: That's a bit extreme - you can pull the slave cylinder and peer through the hole rather than rip the whole lot out. I drilled a 1/4BSP breather hole in the top of my bellhousing, that also lets me look down right on top of the release bearing & clutch. 2 hours ago, FridgeFreezer said: No visible leaks is the key here - it could be weeping at a joint that's also oily, or something bizarre like a pinhole in the rubber pipe that only squirts a little bit out under pressure which then burns off on the exhaust. I'd be cleaning up every joint and flexi with brake cleaner until it's clean and bone dry and then keeping a very close eye on it. Thank you for the input. To try and give everybody a better understanding of my situation the following timeline might help. 4/4/11 86,146 km - Allparts clutch master cylinder fitted. I was about to do a long trip and as the vehicle was new to me I had decided to change out a few components that might give problems. 24/7/19 146,876 km - Upgraded to TRW master cylinder. No existing problems. 28/6/22 151,678 km - Installed AP slave cylinder and new flexible hose. On inspection there was nothing wrong with the items changed. The requirement for continual topping up had started. 17/10/22 152,065 km - Replaced master cylinder with a Bearmach unit. On inspection the TRW unit showed no sign of any leakage. Requirement for topping up continued at about the same level. 27/1/23 152,610 km - Refitted TRW master cylinder and rectified a leak at the upper union of the flexible. By this time the interval between topping up of the master cylinder had reduced, taking about 220 km to completely empty. 10/5/23 153,165 - Removed slave cylinder to check for a leak with nothing detected. All pipes, unions and flexible hose clean and dry. To summarise, I am at a complete loss. All of the work has been done with the assistance of a competent mechanic who is equally at a loss. If the hydraulic fluid is not exiting the system the piston of the slave cylinder should be pushing the clutch release lever against its mounting. Looking at the above I have another flexible hose available and I will try changing that on the off chance. As I have said, when the work was done yesterday there was no visible evidence of any leak but as you point out it is better to be sure before taking the drastic measure of taking the gearbox out. Cheers, Del Quote Link to comment Share on other sites More sharing options...
ThreePointFive Posted May 12, 2023 Share Posted May 12, 2023 10 hours ago, Bowie69 said: If you'd all just see the light and fit an auto, there'd be no more of this sort of nonsense on here.... Mods, we need an 'angry' react button. 2 1 Quote Link to comment Share on other sites More sharing options...
smallfry Posted May 12, 2023 Share Posted May 12, 2023 15 minutes ago, ThreePointFive said: Mods, we need an 'angry' react button. Mods, please ignore this poor deluded fellow. Actually, that is a VERY good idea ! 2 Quote Link to comment Share on other sites More sharing options...
ThreePointFive Posted May 12, 2023 Share Posted May 12, 2023 Don Del - Just a quick thought, unsure of the weather in your part of the world but do you frequently experience Defender Footwell Flooding? If so, that might not all be entirely rain water. I'm guessing you've looked at the outside face of the footwell and there's no obvious trails that side. It's just another leakage route that may not be immediately obvious. I mention it because I think my own clutch pedal is getting a weep from the master cylinder and I misidentified it as rain. 1 Quote Link to comment Share on other sites More sharing options...
smallfry Posted May 12, 2023 Share Posted May 12, 2023 Thanks for the concise symptom timeline. Helps a lot. It is quite a slow leak then. But I would have thought you would still see some evidence. What is the climate like where you are, as I wonder if such a small amount of fluid would evaporate if it is hot there ? Or washed away with heavy warm rain ? It looks like it is a result of something you or a mechanic has done, and as you had a leak at one of the pipe unions, I would look closely there. Possibly the metal feed pipe has fractured at the flare which you will not see unless it is disconnected ? The fluid leak could be in the form of a fine spray, directed away from the vehicle or onto the exhaust, which would cause it to simply vanish ?. A frustrating one for sure ! Quote Link to comment Share on other sites More sharing options...
hurbie Posted May 12, 2023 Share Posted May 12, 2023 can't you just operate the clutch pedal , and put a piece of wood between the seat and pedal , this way it has pressure on it while you investigate. 1 Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 12, 2023 Author Share Posted May 12, 2023 5 hours ago, hurbie said: can't you just operate the clutch pedal , and put a piece of wood between the seat and pedal , this way it has pressure on it while you investigate. Exactly what I have just done this afternoon. A modified version of the old lorry drivers "motorway stick. I´ll attach a few photos below to illustrate. I checked it for an hour and absolutely nothing, zip, nada! All the joints bone dry. When I removed the stick the level in the master cylinder did not go down indicating no loss. I have replaced the stick and will leave it overnight to see if anything happens. The other day when the slave cylinder was removed for checking I noticed that the position of the piston was about a third of the way down the bore which is exactly the same as the position of the piston in the slave cylinder that it replaced almost 1,500 km previously. This would mitigate against there being a problem with the clutch or the operating linkage as the piston should have moved further forward if the additional fluid was being retained in the system and would not have moved back against the spring behind it. I am wondering now whether or not there might have been a leak on the joint where the short section of pipe from the slave cylinder connects to the flexible hose and when the slave was refitted this joint was fully tightened. Depending on what I find tomorrow I intend taking the truck out for a run on the weekend to see what happens. Cheers, Del Quote Link to comment Share on other sites More sharing options...
steve b Posted May 12, 2023 Share Posted May 12, 2023 Might I suggest your twin downpipes directly below the slave may be affecting things? A quick bodge up heat shield cover might be worth a test ? Just a thought. Steve Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 14, 2023 Author Share Posted May 14, 2023 On 5/12/2023 at 5:45 PM, steve b said: Might I suggest your twin downpipes directly below the slave may be affecting things? A quick bodge up heat shield cover might be worth a test ? Just a thought. Steve Sunday update! I left the "motorway stick" in overnight on Friday and removed it on Saturday afternoon after about twenty hours. No noticeable reduction observed in the fluid level in the master cylinder. Took the truck out for a run this afternoon to a supermarket we occasionally use, a journey of about 10 miles and a drop in altitude of around 500 metres. It was an in town trip with fairly frequent gear changes. The fluid level was checked on arrival at the supermarket and no noticeable drop found. After a happy (relieved?) 45 minutes shopping it was back home. Checking the fluid level again on arrival it was found to have dropped by almost a quarter of an inch. The obvious difference between be the two halves of the trip being that on the way back everything was fully warmed up and the engine had to work harder on the climb with a consequent increase in temperature of the exhaust down pipes. I am going to give your suggestion about installing a heat shield a go this week to see if it makes any difference. Watch this space! Many thanks, Del Quote Link to comment Share on other sites More sharing options...
steve b Posted May 15, 2023 Share Posted May 15, 2023 Got to be worth a try. Not sure how easy it would be to source locally but a heat sensitive sticker on the slave cylinder will record highest temperature Steve 1 Quote Link to comment Share on other sites More sharing options...
Don Del Posted May 17, 2023 Author Share Posted May 17, 2023 On 5/12/2023 at 5:45 PM, steve b said: Might I suggest your twin downpipes directly below the slave may be affecting things? A quick bodge up heat shield cover might be worth a test ? Just a thought. Steve I installed a heat shield today, see photos below, and so far so good! A one hour drive of around 12 miles with a 500 metre increase in altitude didn´t result in any reduction of the fluid level in the master cylinder in stark comparison to what occurred last weekend. I am fairly confident that the cause of the problem has been identified and if it recurs on a longer run I am sure that improvements to the heat shield will fully resolve matters. Cheers, Del 2 Quote Link to comment Share on other sites More sharing options...
steve b Posted May 17, 2023 Share Posted May 17, 2023 That is a very tidy looking job, hope it's sorted and I'm not in the least envious that you are in the mountains around La Paz working a V8 If you can post some pic's of your "day to day" scenery I for one would enjoy them. Steve Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted May 17, 2023 Share Posted May 17, 2023 My Tdi used to have a soft clutch pedal the first few presses after a motorway run on a hot day - same problem I reckon. Quote Link to comment Share on other sites More sharing options...
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