Wobsta

So to update and mark (fingers crossed) as solved, I finally got bored of driving around with the EGR vacuum unconnected and investigated further today. For ****s and giggles, I reconnected the vacuum pipe half expecting to be back to the original state of affairs described in the first post, but no, car was exactly as without it connected. Now I know the problem can't be lack of vacuum since brakes, turbo etc still work OK, so still points to a goosed EGR valve or the controlling N18 solenoid, So I put a vacuum gauge on the EGR vacuum pipe, started it up, and gunned it from idle a few times to about 3-3.5k revs. At this stage, I can't say that I knew what I should be seeing but I what I did see was clearly wrong. The gauge sat at around 2 inches and gunning made the needle shake, but it stayed at around the same. Clearly there should be some change there as the alternative is that the solenoid does nothing (clearly not the case). To be sure, I checked the vacuum in, and sure enough I was showing around 27inches there, so all good to the inlet of the solenoid. So, whipped the solenoid off to investigate. I applied 12v to the terminals, and not a thing. Should at least fee a click or hear something, I thought, but no. The N18 I have looks like this (not mine, didn't take photos but looks the same) So, to investigate further, I took a junior hacksaw to the metal band at the tap and released it. The top part then separates from the bottom part. The top part didn't appear to be blocked at all. The bottom half has a plunger the full depth of the bottom half with a red diaphragm at the top where the two parts join (so roughly where that metal band sits). Knowing how a solenoid works, the plunger obviously should move freely. Well, it didn't. So I removed the rubber diaphragm to avoid damaging it, and using some mole grips I removed the plunger. It was very tight, and gunked in there. I cleaned the plunger with some sandpaper and the internal bore on the body with sandpaper wrapped around a screwdriver. Then flushed it with some brake cleaner, dried it, applied some light machine oil, reassembled, put the metal ring back and secured it with a zip tie. Tested it on the bench, got a click. Put it back in the car, connected the vacuum gauge to the EGR pipe, and repeated the gun to 3k from idle, and lo and behold we now have over 15inches at idle and zero with some hefty throttle. So some significant differences in comparison to the previous state of affairs. I cleared the error code, and so far so good. Previously the error would com back within a mile or two, but so far no repeat. If truth be told I'd had an EML light for some time but put it down to the MAF sensor. Clearly I got that wrong. But for the first time in a while I have no EML showing. My guess is that the initial state of affairs I described was caused by the solenoid sticking in the open "idle" position, so that all the boost was dumped out through the open EGR. All seems to be OK for now. I guess it will need changing at some point in the future, but who knows, but might run for 2-3 years yet by which time the car will likely be deceased. Thanks everyone for their help.

So, though I'll not mark as solved yet as it could still be one of two things, I have a functioning car again. Ken, it appears you were correct; I was losing boost, but not through the boost pipes, but rather through the EGR valve it would seem. I put it all back together this morning and for good measure changed out the fuel and air filters (the latter was past its best - I live up an old unmade dusty road, so should probably halve the recommended service intervals). Anyway, I didn't expect that they would, but no difference was noticed. Then I removed the vacuum pipe from the EGR valve - back to full power again. I have to investigate further though as I think it may be the solenoid rather than the valve - perhaps someone can help? Should there be vacuum at the EGR valve at idle? Fro what I've read I think that's a no. If that is the case I believe the solenoid is shot rather than the valve as without vacuum, all is well. In any case I think I'll just delete the EGR going forward, but would like to know what caused the problem. Back on the road in any case. Will update after confirming valve/solenoid options.

Ah just realised that that part on the inlet manifold includes the exhaust gas recirculation. Maybe that's what I'm seeing coming from the inlet manifold, some exhaust. It looked exhaustish.

Yeah I know, but there's not much else I can do today. I figure it's better than nothing. stuff sticks like the proverbial brown stuff and sets nice and hard so it can only improve things I think and I have a massive tin of chem metal . If nothing else the vacuum hose will actually stay in the hose clip now since it's thick enough. It's not a permanent fix. I think it;s just the vacuum to the anti shudder valve in any case.

No it wasn't. It was still intact though very weak so I've bodged it for now with some chemical metal. It isn't the turbo though, or it least I very much doubt it is. I popped the top left rubber elbow/boost pipe twixt the inlet manifold and the plastic part and also popped the cold side turbo to intercooler pipe under the car, and I can feel air blowing from the turbo when gunned, also looks nice and clean in there which isn't what I would expect if it had failed. Guess it could just seize though and look clean, but as I say there's a pronounced volume of air coming out the cold exit side and no odd sounds which is a good thing I think. Not very scientific but the best I can do under the circumstances. I did however notice with the top elbow off that I have something (smoke/steam?) coming out of the inlet manifold which seems wrong given that the correct direct is inwards. Makes me think maybe of manifold/head leaks, maybe timing, or an inlet valve not closing sufficienty? I guess any of those would explain the lack of performance. I don't get smoke out of the exhaust either with the two pipes disconnected or not that I noticed. When the performance first dropped off the cliff, there were clouds of black smoke too, but not so much now. It's still not good, but it doesn't kill the local wildlife. Any further thoughts? I'll probably have a look at the timing tomorrow, but I guess it would be a compression test if valves aren't working properly.

Can't see anything obviously adrift there, did notice this, don't know if this is of relevance. Photos aren't great but you make out that one of the pipes is damaged, and the electrical connection is almost worn through also. I've removed it just to get a better picture of what it is, but since it;s directly connected to the valve/gate on the intake (is that the throttle body?) I guess it could be. If that could be a cause, is there a way to test?

A couple of photos. I'm guessing the oily pipe connected to the air intake hose is for burning crankcase emissions and would likely be unrelated, but the round thing on the right hand side of the block (also oily) has to be a vacuum pump since it's connected to the brake servo. I presume that boost is regulated by vacuum too, so maybe worth checking the vacuum pump. A couple of days before Xmas I did have an intermittent hard pedal. Is that related perhaps? I expect the way to check for a non obvious leak would be to pressure test, which of course I can't do. To be honest I generally leave engines alone other than servicing though I'm quite happy working on the running gear. It does seem to be a lot more complicated than the last diesel I worked on. Only really having a look as the time of year means I can't really get it in to a garage yet.

Have read of a few similar cases. Having read about how the setup works though, I guess my theory regarding the turbo being OK may be flawed. I guess the ECU could be underfueling (though black smoke implies unburned fuel I think) so maybe not enough air (scratches head). Air filter sure needs changing but I did run it briefly without the air filter on and the same problem was there from memory.

As per title, starts and idles fine. No funny noises really at idle, just sounds like the tractor that it is. KI can just about move the car on a flat surface at low speed but as soon as you put the engine under load it will just die. And there will be quite a lot of smoke and it does sound a little odd - almost like listening to the engine as though it's "baffled". I think it's something that's been deteriorating for a while as I had noticed that I had to boot the car a little more than usual up the many hills that there in these parts and thought I had seen some smoke in the rear view, but initially it was that gradual that I sort of doubted myself. I've never really had problems with a turbo, but to me this doesn't make sense that it would be a dead turbo, as I would expect some performance from it in the lower rev ranges before the turbo kicks in? Any ideas?

So yeah, IR thermometer located and used, not solved, but much improved. There's a difference of maybe 20-40C between the two fronts. If i recall correctly as well, previously the binding side ran a little hotter too though that could be a false memory, galloping senility and all that. I figure though that the servo at the very least has to be at fault because being that there is no solid connection between the servo push rod and the master cylinder socket, tapping the brake pedal up should have zero effect on the master cylinder if the master cylinder was sticking. It doesn't of course rule out that the master cylinder could have a fault of its own though. So, on to the second test of cracking the master cylinder bolts a turn or two.

I doubt the tiny spring or my foot hooking would be enough to snap the plastic bit. Having read some other posts on removing the brake pedal they deem seem to concur with your "fiddly" assessment so I'm planning on leaving that well alone. Two things make me think it's not the master cylinder is that hooking the pedal or the added spring seems to improve matters and that it only affects one front disc. Of course though, if the fault is that there is no clearance between the servo push rod and the master cylinder socket and the master cylinder is slightly activated, then it would make sense that both would bind too, but having had a look at this video: which looks like the master cylinder I have, there is a spring between the first and second pistons, and presumably a spring after the second piston which we don't see (no need to remove it I guess to rebuild, but I can't see how the second piston could retract without one ). I can theoretically see how a slight imbalance between those two springs would mean that the brake fluid transfer ports could open a fraction apart from each other. In the big scheme of things this would be unlikely to make any difference provided the master cylinder is free to move back to a completely inactive position. If however the push rod is applying a the tiniest amount of pressure, then perhaps one port could remain closed. I have found some details of a similar problem here: http://www.bba-reman.com/forums/Topic113057.aspx which describes almost perfectly the issues I have. I haven't checked the rear drums on mine, but since they aren't applied anywhere near as much as the front discs are I wouldn't expect to see as noticeable a difference in any case. In this case, two similar issues are described, and servo is diagnosed as the issue. I did also come across this: http://bigcoupe.com/phpBB3/viewtopic.php?t=16351 Of course this is on a BMW, but it also reports a faulty master cylinder that causes both discs to bind, but if you have a look at points 11 & 12 the author describes a potential situation discovered by dismantling a master cylinder that could cause a one sided bind. All that said, I think it's the servo being partially activated (and by dint of that the master cylinder too) because, as an update, the spring has now been on for 50 or so miles, and by my temperature assessment using my hand, it seems to have solved the problem though as one might expect the brake pedal action is now a little less than progressive at first application though I'm getting used to it. So back to diagnosis. I'll get by IR thermometer on the front wheels shortly and see how accurate my hand assessment is. Thereafter I'll crack the two master cylinder bolts to see whether it is indeed the servo or the master cylinder. If the latter, I'll likely live with the spring arrangement or maybe bodge something better as replacing the servo on a car this old is rather pointless. It'll likely be going to the scrapyard in the sky in the next year or so in any case as new servos are prohibitively expensive, and the ball ache involved in swapping a scrapper part over in lieu of what I have seems a potential waste time due to unknowns of second hand parts, plus of course it's still a significant amount of time even if it works when application of a spring seems to do the trick. I'll report back in a few days (or weeks if I get lazy and learn to live with the spring).

Hi, For reference this concerns a Mk1 1u5 Octavia Estate, though I ask as a general query as I imagine braking systems are not that dissimilar across the marque, or indeed across all marques. I have a binding left front brake. It isn't significant, bad enough to wear the pads that side prematurely, maybe 2-3 times as fast, and decrease fuel consumption by 4-6mpg. The wheel is noticeably hotter after drivcing. Dragging would maybe be a better description rather than binding. I hadn't really noticed until my tame MOT tester pointed it out some time ago. I have been trying to track the problem down since. So far, I have fruitlessly changed caliper, flexi hose, bled that side countless times, cleaned and greased pins. Bled master cylinder etc; all the usual culprits that I can think of have been tested/changed to no avail. The master cylinder itself is newish though not OEM (4-5 years maybe - changed it after local garage goosed the original factory part), other than it's all standard. I should add the car stops as expected, the pedal is good and not spongy and I don't notice a pull to one side. I wouldn't say I'm at my wits end as changing brake pads more regularly is hardly a major inconvenience since I DIY, but I don't really want to throw more money at it without a more solid idea of the issue. So, I have been investigating over the last few days. When the brake is dragging, if I crack the bleed nipple open, a little fluid spurts out (fnarr fnarr). This suggests that there is residual pressure in the brake line, and that the issue is not mechanical. After releasing the pressure, the wheel frees. I had noticed that things improved if I hooked my foot under the brake pedal and pulled up, that things improved (tested many times after coming to a halt at junction, releasing foot brake and remaining stationary, then hooking the brake the car would move). So, on realising this I added a brake pedal return spring. This has improved things greatly and although I haven't lifted that corner to check for bind and that corner is still hotter, it is noticeably better than without the spring. Thoughts? So my mullings. This is a tandem cylinder I believe, and have read reports on other vehicles that return route for brake fluid can be marginally different for each piston in the master cylinder I wondered whether it could be a faulty master cylinder. I have had an issue before where both front discs would bind and resolve with application of hooking, but that was fixed with the current new master cylinder. It seems unlikely that a master cylinder could cause just one to bind? Having messed with the master cylinders (both old discarded and current new), the return spring in them seem quite strong, so I don't see how either of the former scenarios I describe could be the case, though at least one has in the past. Since there is no return spring as standard the brake seems reliant on the servo(is there a spring therein) pushing it back or the master cylinder spring doing the same. IN any case so far, no matter how hard I pull the brake pedal so far, it doesn't seem possible to completely prevent the bind, The servo in the bulkhead appears to be some kind of ball and socket, so there is no potential to adjust clearance. The isn't, that I remember, any means to adjust clearance between servo pushrod and master socket interface and since I don't appear to be able to completely eliminate the bind it would appear that there is at least a very minimal connection. I guess a test I could do is when dragging (after some town driving is best), I could quickly crack the bolts a few turns on the master cylinder to provide a little more clearance and see if that frees the wheel completely. If it does, it would seem to indicate a malfunctioning servo. Can anyone else think of anything to try?

Just top add another pretty much identical situation. Garage bled the system incorrectly, and the brakes were binding. Fixed with new MC. Can be read about here: http://www.briskoda.net/forums/topic/364777-adventures-with-brakes-or-why-i-hate-garages/

Talking to myself now - it is indeed 7mm on the drums.

The reardrums look to be 7mm or thereabouts which seems to be an odd choice. Haven't got as far as the fronts yet but would guess they would be the same anyhow. Ideas?