Cracked Wastegate Symptoms
Sara Legath
Driving a vehicle with a turbocharger is very different than driving without one. If you have experienced this before, you will know when the turbocharger in your vehicle is not working properly. If the turbo does not engage when you apply full throttle pressure to the engine, the boost is not being produced.
While there could be numerous reasons this is not working properly, one of the most common is the wastegate is failing. In most situations, it is not functioning properly or there is a blockage in the hose. Once this is noticed, it needs to be fixed immediately. Additional damage could occur to the turbocharger if this is not dealt with.
Keep an eye out! Pay attention to how your car is driving and any differences you might notice in your overall vehicle performance. It just might be paying attention that leads you to catch one of these symptoms of a failing wastegate. And just like any situation, the sooner you catch a problem, the faster you can fix it at a turbocharger repair service!
Does the engine actually lose power when the MAP gauge shows the reduction? If not, I would suspect some fluid in the MP line that manages to block the line when in the nose up attitude. I'm not familiar with the Continental turbo controller setup, but if it was on my lycoming I'd be tempted to check all the controller/wastegate/feed/control/scavenge hoses for kinks/blockages or maybe purging for air
Pretty hard to diagnose over the Internet, but I have two thoughts, and I have to preface it by saying I am not a mechanic nor do I fly a 252 ( I have a 231), so take my comments for what they are worth.
It sounds to me as though you have a wastegate control failure, the question is whether it is the wastegate or the controller. It sounds more like thecontroller to me. It sounds as though, when heat builds up after a period of operation, something is happening in the controller. But just in case, I would have your mechanic perform a long full power maintenance run-up on the ground, long enough to create the heat build-up. If the MP falls, then you know it is the heat build-up. This would rule out that any altitude change on take-off is causing it. I suppose its possible an ambient pressure change is causing something to happen in the controller, but not likely, so I would just do the run-up to rule it out. If the MP does not fall during the run-up, then it is going to be some kind of pressure sensing issue.
After that, there are two possibilities in mind. One, as I understand it the controller is hydraulically operated (pressurized engine oil, I think), so it could be something in the hydraulic system, a valve or control gate of some kind. It could also be purely physical binding of the wastegate due to heat expansion. But I don't think the second possibility is it. Unless you are doing something with the MP, prop, or fuel controls at the point where this happens, if the gate itself is binding, one would think it would just stick where it is, i.e. closed or mostly closed, and you would have full power but would have difficulty reducing power. So it sounds to me like it has to be something in the controller or the hydraulic system that causes hydraulic pressure to the wastegate to fall, in turn allowing the wastegate to open when the engine gets hot. That's all I can think of at the moment.
An instantaneous drop to ambient air pressure suggest a huge induction leak. The fact that it comes and goes points to the overboost valve popping open prematurely. Check that since it can cause your symptoms.
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Yes it does, you don't get any 'kick' from the turbocharger, that usualy makes it's presence know around the 27". But I do guess the fault lies somewhere hidden in a hose or linkage. All the components themselves check out fine.
Can't say that I did. I did a trial run yesterday and now the wastegate remained open, so I had to reject the take-off. I was suspecting that may be with a colder engine/engine-oil I might get the same results as I did Saturday (36" take-off and then a reduction to 25/26" WOT), but the wastegate remains open all the time now.
Thanks again for you input, the wastegate moves freely and without any problems. It has been overhauled along with the controller by Main Turbo, the controller was sent back even, and replaced with another item. Great service from Main Turbo! My mechanic wil be on the telephone with Gary (Main) today, I hope he can shed some light on the matter.
No. The overboost (valve/ regulator) is the can on the top of the engine on the right. It is attached to the induction system. On your engine it will open at 37". This could explain why you initially got full power, but it opened and failed to reseat. It's possible that once you shut down and let it sit, the valve reseated, but it is clearly still faulty.
your shop should have or should be able to make a cover to replace the overboost valve. Fly with it removed, and see if it is the malfunctioning piece. The symptoms sound like it is, and it's a lot cheaper than removing and shipping out wastegate/controller.
Well, that ship has sailed... It has already become very costly. I've asked my shop to check the O/B valve out. But is there an overboost valve on a automatic wastegate system? Guarding against overboost, Isn't this the work of the wastegate?
An overhaul of those components does not guarantee that they were repaired properly. I had a problem with my 231 where the MP would drift. It would increase slowly at first and then pretty quickly as MP increased. My wastegate was sent off for overhaul and came back with the same issue. When I spoke to Merlyn they acknowledged that when they bench tested it there was a pin hole leak in the bellows but it was within spec so they didn't replace it during the overhaul. I sent it back again for repair and the second time it came back fixed. I would question what was replaced at overhaul.
The waste gate is spring loaded open and has to have oil pressure to close it. The controller releases that oil pressure when it needs the gate to open. Cap the line going from the waste gate to the controller and the waste gate should close. A pressure gauge instead a cap on the line can tell you if there is oil pressure down stream of the waste gate and upstream of the controller.
Here you can see the start and end of the full throttle period marked by the target boost (pink) going from zero to 14.5 and then slowly reducing and then me coming off the throttle and the target dropping off immediately.
If your graph is bad, the first thing to do is to start driving VERY gently, by which I mean, no more than 20% throttle (ish). Keeping the throttle plate open as little as possible will prevent this kind of over boost. You then need to get the wastegate freed up, mine was so stuck it needed a specialist turbo reconditioner to get it working again, but now, it drives like a charm.
So my car has been boosting to around 12psi no matter what setting I put the boost controller on... I removed the apexi boost controller and put a new hose with new hose clamps straight from the wastegate actuator to the intake piping. Car should be running 7 or 8 psi now like stock.
Has always done this since Ive had the car, which has been only a couple of weeks. I thought it was the boost controller not working properly so I removed the boost controller and it still over boosts.
Actually Ill move it by hand and measure the throw, then ill put compressed air to it and measure the throw. If the throw is less with the air then the actuator is stuffed. If the throw is the same then something is stopping the wastegate from opening completely and will probably need turbo out to inspect.
Hooked the air comp up to the wastegate and the rod moved the same amount that I can move it by hand. (If I grab the rod with pliers I cant move it I have to grab the connection at the turbo and twist, should it be easier to move?)
Personally I'd try taking the c-clip off the actuator arm at the end where it kind of bolts onto the gate, then see if you can turn the little flap easily enough by hand, it should just be loose as anything.
If you want to run the higher boost, try gapping your plugs closer together. The standard coils can't deliver enough spark when there is higher boost so blows out the spark. If you reduce it to 8 mill gap if i remember correctly this should give you enough to run the higher boost.
I had this happen a few years ago, but have started to have the problem where I go full throttle, but boost only goes up to about 8 psi and stays there. I can often merely lift off the throttle a second, step on the gas again, and then it climbs to full boost like normal. Sometimes it goes away for a day or two, then comes back.
If you can log your "WGDC actually", then you can see if it's roughly where it should be. If it is, then likely it's something else besides the ecu/map....e.g. it may be a stuck actuator, leak, etc. I'd log rpm, throttle position, manifold pressure, target boost, wgdc actual.
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