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Hydrolock Help!

Old 04-06-2005, 11:39 AM
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rodzilla
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Default Hydrolock Help!

Just got my rc10gt last week and I fired it up for the first time on Monday, I looked at it last night and now it is hydrolocked. From reading on this forum I believe I know what hydrolock is and how to fix it now, but my question is why did it happen and what can I do to make sure it does not happen everytime after I run the car? When I was ready to shut it down I let the car run out of gas, then I tried to start it a few times to try to burn all the gas out of it and then I put afterrun oil in through the carb, about 4 drops.

Thanks!
Old 04-06-2005, 12:19 PM
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enjoymentboy
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Default RE: Hydrolock Help!

Hydrolock happens anytime you fill your combustion chamber with a liquid. Since it is not compressable the piston can't go any further. Remove the glow plug and turn the car upside down. Turn the engine over a few times and you should cealr the cylinder. Put the plug back in and you should be okay.

To keep it from happening again, don't use so much ARO or don't tune your carb so rich. That's generally when it will happen. If you cansisnently get hydrolocked at start up you are most likely over priming and "may" be set to rich.

Enjoymentboy
Old 04-06-2005, 12:39 PM
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aknitroguy
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Default RE: Hydrolock Help!

If it was cold out and your engine is new it will "pinch" the cylinder on a new motor, after you do what enjoymentboy said, if fuel don't spray out the glow plug hole, you might try loosening the plug just a touch and heating the cylinder head with a hairdryer, The heat will expand your cylinder, and loosen the stuck piston. Start the engine, then tighten the plug back down. I run a lot in cooler weather and til your engine is broken in this may happen several times. once it starts make sure the engine heats up before running it hard. Hydrolock and cold weather/new engine pinch are about the only two things it could be, exept of course for broken internal parts and or a defective engine, but if it's the stock engine, it should be good to go.
Take care,
Jay
Old 04-08-2005, 11:58 AM
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Bucknut
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Default RE: Hydrolock Help!

I had the same problem with my RC10GT a couple days ago.....(hydrolock is when the pull start won't pull because the piston is stuck in the cylinder, right?)

I ended up taking off the head and sliding the cylinder out and cleaning it up with some fine grade emory cloth.....for some reason the piston kept getting stuck when it got to the top of the cylinder.

I cleaned it for about 15 mins, put it back in and it was still sticking - but I could tell it wasn't as bad, so I cleaned it for about 15 more mins and it worked.
Old 04-08-2005, 05:08 PM
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Default RE: Hydrolock Help!


ORIGINAL: Bucknut

I had the same problem with my RC10GT a couple days ago.....(hydrolock is when the pull start won't pull because the piston is stuck in the cylinder, right?)

I ended up taking off the head and sliding the cylinder out and cleaning it up with some fine grade emory cloth.....for some reason the piston kept getting stuck when it got to the top of the cylinder.

I cleaned it for about 15 mins, put it back in and it was still sticking - but I could tell it wasn't as bad, so I cleaned it for about 15 more mins and it worked.
Nearly right, hydrolock is where there is an incompressible liquid - (fuel) in the combustion chamber. The engine cannot "turn over" because the piston cannot move any further up the sleeve as it cannot compress liquid, there is just too much pressure. As previously stated, it happens when there is too much fuel in the combustion chamber (too rich) and will prevent the piston from moving.

What i believe you are talking about is pinch, the sleeve is tapered (becomes narrower) at the highest point that the piston will reach during a combustion cycle (top dead centre). This provides a better seal between the piston and liner and aides compression, as fuel/air is less likely to be able to squeeze through the gap between the two components.
This is usually most noticeable in brand new engines, after run-in it usualy losens a bit as the piston/liner bed together.
If you could not turn the engine over at all (the piston got completely stuck) without the glow plug attached then you have solved the problem. If you mistook pinch for compression (you could not turn the engine over with the glow plug inserted) you may have ruined your engine (no compression, no combustion cycle).
If the piston did not got stuck, but only became harder to move at TDC, then you have removed the pinch and have more than likely shortened the life of your engine. It is there for a reason. Modifying the piston/liner without knowing exactlywhat you are doing, and how it will effect performance is never a good idea.

Hope you ticked box number one... Good luck.
Old 04-09-2005, 08:52 AM
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Default RE: Hydrolock Help!

Ahh, ok so that's what hydrolock is.......no, I don't think mine was hydrolocked - the first thing I tried was taking out the glowplug. It was still stuck and every single time that the piston got to the top it was sticking....to the point where it wouldn't budge at all. So I had to turn the starting axle without the head installed and at the same time pry the cylinder up with a small screwdriver.....performing both actions at once seemed to make it easier.

I can't think of any other thing that I could've done to stop it from sticking, and I don't see any evidence of engine damage - I think if I sanded down the cylinder too much (that's why I tried it every 15 mins, I definetly didn't want to overdue it) and lost compression that I'd see signs of it by now - but it's running great.

btw, what could have caused the "pinch"? It happened while trying to start it, it wasn't even running and all of a sudden the pull start wouldn't budge! I don't use afterrun oil.....maybe that would prevent it?
Old 04-09-2005, 09:22 AM
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Default RE: Hydrolock Help!

Did it become difficult to start the first time you tried to start it (i.e before run-in?) Or was it after the engine had been run a few times?
Usually engines have the greatest amount of "pinch" when they are brand new, so on every run this should decrease a little. But yes, if there had been fuel/oil in the engune previously then you might not have noticed it (lubes the piston/sleeve so they slide past each other more easily). A lack of oil or fuel (which obviously contains oil) could have made the pinch more noticeable when you tried to start it. If it is difficult to start (because of the pinch) in the future try adding a couple of drops of oil into the glow-plug hole, and turn the engine over by hand a few times to lubricate the piston.
Good to hear you solved the problem and it is now running great.
Old 08-31-2021, 01:50 AM
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Originally Posted by Bucknut View Post
Ahh, ok so that's what hydrolock is.......no, I don't think mine was hydrolocked - the first thing I tried was taking out the glowplug. It was still stuck and every single time that the piston got to the top it was sticking....to the point where it wouldn't budge at all. So I had to turn the starting axle without the head installed and at the same time pry the cylinder up with a small screwdriver.....performing both actions at once seemed to make it easier.

I can't think of any other thing that I could've done to stop it from sticking, and I don't see any evidence of engine damage - I think if I sanded down the cylinder too much (that's why I tried it every 15 mins, I definetly didn't want to overdue it) and lost compression that I'd see signs of it by now - but it's running great.

btw, what could have caused the "pinch"? It happened while trying to start it, it wasn't even running and all of a sudden the pull start wouldn't budge! I don't use afterrun oil.....maybe that would prevent it?
Wondering if you solved this problem.

I have had a Cen CT4S in storage for many years but always maintained with after-run oil etc. I completely pulled apart and rebuilt the engine but cannot get it to start. I can only think that the piston pinching is the problem. I recently purchased another CT4s which has an engine with internals that are in almost new condition, but I am having the same problem. I have ruled out fuel, glow plug, engine temperature, carb settings etc. Would love to get some insights on this.
Old 08-31-2021, 02:27 PM
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1QwkSport2.5r
 
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If you’re talking about the nip at just below Top Dead Center, that is indeed normal and very desirable. Preheat the engine to 200°F before trying to start it and that problem won’t be a problem anymore. The cylinder expands at the top with heat reducing the mechanical pinch. The longer your engine retains that pinch, the better off you are because it means the e fine is still in like-new mechanical condition.
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Old 08-31-2021, 03:26 PM
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Originally Posted by 1QwkSport2.5r View Post
If you’re talking about the nip at just below Top Dead Center, that is indeed normal and very desirable. Preheat the engine to 200°F before trying to start it and that problem won’t be a problem anymore. The cylinder expands at the top with heat reducing the mechanical pinch. The longer your engine retains that pinch, the better off you are because it means the e fine is still in like-new mechanical condition.
Thanks for the feedback.

COVID has meant over 200 days of lockdown here in Victoria, Australia. Hard to afford parts due to loss of income, but easy to connect with people like you that want to lend a virtual hand.

My remaining tests-to-start will be:
1 - Re-test pre-heating engine to 200F / 96 C
2 - Source O.S. A5 glowplug instead of A3
3 - Get another fuel to rule in/out
4 - Re-Calibrate the carby
Old 08-31-2021, 07:09 PM
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Most car engines run well on a medium heat plug. If using 15% nitro or more, it’s highly advised to use a medium heat plug. Airplanes benefit from scorching hot glow plugs; trucks do not.

Sorry to hear about the lockdown. I know how that goes though - the COVID thing stinks to high hell and I’m surely ready for it to be done and over with. Want to get out a d run my models too. Haven’t burned an ounce of fuel this year.

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