View Full Version : Help: EA81 overheating
08-26-2004, 05:36 PM
Today was a perfect evening for flying. I went up and after 15 minutes the EA81 EIS started flashing red!! The coolant temperature was climibing past 210! I quickly landed and noticed the coolant overflow container was slightly higher then when I first took-off. I added coolant to the engine, went back up, same thing happened after exactly 15 minutes!!! Any suggestions on what to do next?
08-26-2004, 07:52 PM
I had an old Mazda pickup, the same thing happend every 4 or 5 years. The radiator would get plugged up causing high engine temp & blowing all the coolant into the expansion tank. One time the expansion tank overpressured & blew the top off. This caused coolant to spray on the windscreen, I thought the radiator blewup. So when I noticed the engine starting to run warmer I pulled the radiator & had a radiator shop boil it out.
08-26-2004, 08:10 PM
Randy, , 1-another source of quick heating if nothing else was changed is the head gaskets. The coolant will become pressurized from escaping compression of the cylinder. It is forced into the water jackets under the head gasket or it will suck water or steam into the cylinder during the intake stroke. Some beginign signs are the spark plug on the cylinder with the blowby will take on a very very clean look. It is being steam cleaned while you run the engine. sometimes it is noticed in water running out your exhaust pipe.
2-engine thermostates can stick and become problems,9the easy repair, 3-water pump or slipping belts, What ever you find let us know because this is getting to be a popular engine. We need to track it well. Mike Morgan changed the radiator I believe to correct a heating problem on his. Check out his thread, lots of good information.
08-27-2004, 01:56 AM
Randy, what radiator are you using? Where is your temp sensor installed? Where is your Rad. cap located? Do you have a stock Sub intake with thermostat or where is your stat if any?
There is a small water nipple that sticks out the top of the engine block. Where does yours go to? Dave D. recommended I pull this nipple & tap it to 1/8" pipe thread. I then installed a nipple with a tee on it. In the end I installed my temp probe. Out the side of the tee I installed an angle hose barb fitting. That hose then goes back to my fill/ expansion tank.
This way the air is constantly forced out of the engine block & back to the resevoir. Also this keeps the hottest water at your sensor.
Even with a 1 quart aluminum fill tank only partially filled my cap is still venting off the expanding coolant even though , with no stat, my temps are barely reaching 180. I am now going to install an overflow bottle to keep this stuff off my machine. I have a Rabbit rad.
I think this system is working fine, I am just a little concerned about this blowoff situation. Let's try to figure out these problems.
08-27-2004, 05:35 PM
Maybe a little H2O2 tip jets on our rotorblades would solve this?
08-28-2004, 03:02 AM
Purge the system I think is air traped. Becasue if it was working ok unless your coolant is old it should be fine. But if it over heat too much you will be force to change gasket. Now the oil looks ok? I know you measure water temp. but do you have an egt or cht, wondering what they are doing when this happen.
also if it get hot that fast you can run it on the ground for test. It should do the same
08-28-2004, 08:51 PM
If you have a holley carb on the engine and it has poped back, check the accell pump diaphram. They will rupture on a back fire and lean the engine. One other thing to check is the manifold and make sure it has remained torqued. The bolts will loosen and allow air to cause a lean condition.
08-28-2004, 08:53 PM
I forgot to mention the timing. The single bolt hold down will sometimes allow the timing to slip. This will cause an over heating condition very fast!
The small 6mm pipe in the middle of the engine bloc is a vent pipe.
The water coming trough is water from the water pump on its way to cool the right handside of the engine. This water staight from the water pump has the same temp as the cold waterside of the radiator.
A water temp sensor measures in this location the water temp after the radiator, but NOT the engine temp.
The place to measure is where the water goes to the hot side of the radiator and this as close as possible to the engine.
08-30-2004, 03:42 PM
Boy do I ever feel stupid! A better pre-flight by me would have solved this problem over a week ago. A plastic tie wrap was used to secure the coolant hose and oil cooler hose to the lower mast. The tie wrap was so tight that it collapsed the coolant hose against the oiler coler hose and was restricting the flow of coolant! After I fixed it, I went flying for an hour and half. The temp. stayed between 186 and 196.
08-30-2004, 04:59 PM
OK, , That was easy!
08-30-2004, 07:42 PM
Gee Randy, that makes me feel good. I thought that I was the only one who made silly mistakes!!! LOL
08-30-2004, 08:15 PM
thanks for posting the answer to your problem, this may help someone else trouble shoot their engine.
08-31-2004, 01:25 AM
Randy, I am interested to see the answers to the questions that I asked you. Could you please post them?
Jos, where do you suggest reading the coolant temp then? The last place my coolant leaves the engine is at the flanges on the intake(Souza). With a stock intake ,I would just use the stock probe placement in the water passage in the intake?
The left side of the engine gets the cold water from the radiator immediately from the water pump also at the left side.
The right side gets the cold water over the engine in a crossover casted pipe inside the enginebloc This can be seen when one looks carefully at the upper surface of the bloc.
This means that the water is already warmed up from the engine bloc before it reaches the right side of the engine.
Carefully measurements (two temp sensors) show that the right engine side is always warmer. We had engines with 7 degrees C difference between left and right.
An engine seizure on ea71 or ea81 happens always at cilinder nr one.
The temp sensor should read the right side temp, so the sensor must be close to the water outlet on the right head or where right and left join.
08-31-2004, 02:40 AM
Randy, what radiator are you using? I honestly don't know, Ernie Boyette would be the one to ask since he built my gyro.
Where is your temp sensor installed? The sensor is installed in the base of a adapter that I believe is used on the SUB4 conversions. It is on top of the engine, left side when looking at the gyro from the rear.
Where is your Rad. cap located? On top of the engine on the adapter mentioned in the last answer.
Do you have a stock Sub intake with thermostat or where is your stat if any? I do not believe it is a stock intake. The thermostat is inside the adapter just above the sensor. The adapter that houses the thermostat and sensor is a cast aluminum piece. Hope this helps but I would ask Ernie if you want more detailed info.
There is a small water nipple that sticks out the top of the engine block. Where does yours go to? I am not aware of this on mine.
09-01-2004, 01:51 AM
Wow , a SUB4 single place! I'd bet you have plenty of power. Do you have any close up photos you can post? Thanks
09-01-2004, 02:22 AM
It is not a SUB4 conversion, it is a dual carb 100 hp Japanese import EA81 with some SUB4 parts. The thermostat housing might be the ONLY SUB4 part on the entire engine. I really don't know since I did not build it. I wish I had/could build something this nice, I heard it placed reserve grand champion at Mentone! That was just days before Ernie delivered it to me on his way back to Florida.
If I can figure out my digital camera I will post photos of it and hopefully some shots from the air. I am a little nervous about taking photos while flying!
For more information on the autoflight reduction gearbox, go to this link.
09-01-2004, 02:25 AM
Hey Ron A., look what I found! Neat trailer.
09-01-2004, 04:12 AM
wonder why it doesn't have Dragon wings on it?
09-01-2004, 04:31 AM
I just re-read the ad, didn't realize it until you mentioned it. Makes me wonder to. Maybe he destroyed them and was too embarassed to tell Ernie he needed another set!
09-01-2004, 04:46 AM
After seeing that trailer and the rotor blades attached, I asked Ernie about hauling a machine with the blades attached. Ernie confirmed that this can damage both the blades and the rotor head bearing. So whoever buys the machine may have some problems.
09-02-2004, 11:24 AM
we are used to traile them taht way. But you have to make sure you let the holding poles move with the bounce of the trailer. Can not be tight. Yes if it shakes left to right will eat up the bushings.
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