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532 overheating

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Posted

OK guys we have had an issue with GLMMCMINN's 532 overheating in his Avid "A" green turd.  We replumbed it with larger tubing, put by pass lines on it so the inside cabin heater core only got "bleed" water, ripped out the two inside the cowl radiators and went to a belly mount radiator.  Yesterday wa the first flight with the new belly mount radiator.  Outside temps were ~ 32 degree so we figured we would end up taping up the radiator...... well shit.. first flight I was on a shallow climb out and the temos were creeping up on me.  GREAT... hit 195 deg. on the down wind even with the power pulled back to about 5200.  We loaded it back up and went back to his house for more beer drinking and ass scratching.  One of the guys was looking the system over and suggested that we put a shut off valve going to the cabin heater core to force all cooling fluid through the main radiator ( I just have to add that I had taken the shut off valves to gregs house weeks ago to be installed but he had not put them in yet)......  Soooo. we take it out side, tie it down and fire it up.  With the valve open and water going into the cabin heater core the temps started creeping up on us... I reached in and shut the valve and IMMEDIATELY we had a 30 degree temp drop...

Today I am gonna go grab it and take it for a flight (while that poor bastage has to work :lol: )  Hopefully this will cure the problems that have been keeping him grounded for the last year. 

Just tossing this out there for anyone who may have been dealing with overheating issues and you were at your witts end... I would have never thought that a 1/2" line teed into the 1" main lines would have bled off enough coolant to the cabin core to cause the overheating issues, but ground testing lastnight showed a huge difference with the cabin core bypassed.

:beerchug:  < to what I hope to be the last test flight before Greg's get to fly in his own bird

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Posted

Can we assume that the system is/was filled with coolant with the valve open (so as not to short change the main radiator when it does get open?)

Just thinking out loud here.....

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Posted

Understand I know nothing about Avids and 'specially 2 strokes....,  :hammerhead:

But, again, just wondering aloud...... Is the heater core in series with, or parallel to, the radiator?  Installed in series, all coolant flows through the radiator.  Installed parallel, the total flow will be divided between the two when the valve is "0n".  (less flow through radiator)

I'm just thinking in terms of electric flow, but the principle is the same....eh??  Pump pressure would factor in too...

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Posted

  :2cent:    Could it be the loose nuts behind the stick or the :beerchug:  or to much  :sharedoobie:  wahtever it is im shure you will figure it out  :banghead:

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Posted

The heater core was installed in series the first time... then it was changed to go in parallel with the shut off valve... while the temos initially started off nice and cool with the ground runs, the bitch still overheated in the air... this was flight #7 that the bastage tried to kill me with engine that wanted to shit the bed.. Lastnight we replumbed it with nice big sweeping 1" hoses and no sharp 90 Degree bends.  No heater core just the engine and a nice big belly mount radiator.  Radiator has been flow tested, system has been burped up the freeking wazzoo so I know we dont have any air in it.

The system up to this point was plumbed in with alot of copper pipe that had quite a few 90 degree bends in it.  I am hoping that the many flow direction changes were slowing the coolant down.  We do alot of piping systems at work that part of the de-bottle necking is removing flow direction changes from the systems.  I am hoping that this change will do the trick for Greg cause he really really really wants to be flying his own plane, and I want to stop shitting myself everytime the temp gauge reads holy crap you need to land now.

With just a tiny touch of good luck, we should know in a few hours if the changes last night are going to solve the problems and he will get his first ride in his own plane.

:beerchug:

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Posted

Well shit... we replumbed the engine and the way it is run now it should have never got above 120 as the other planes here that are plumbed the same way we had to block of most of the radiator to get it to come up to temp... We did a ground run at the house with no issues, took her out to the airport ran it up again no issues... so I strapped in and tried to kill myself again.  Temps looked good, taxied down to the end of 07 took the runway and firewalled it... temps looked good broke ground started a shallow climb to keep maximum cooling flow and at 200' the temps started coming up... way up.  The water pressure came up to 12 PSI and then the temps went to 210 and I pull the power WAY back, leveled off flew a very short pattern and brought it in... of course on the taxi back the temps settled back to a nice 150.  WTF... soooo I pull in and pop the cowl and checked fluid level.. she was a bit low so I figured we just did not get it burped good enough... more burping, more fluid, more ground runs and I figure what the hell a cat has 9 lives, I have used 8 of them so far on this plane so I had another free shot left.  Same story, about 3-400' temps start coming back up, this time to 220 and she blows antifreeze all over the side of the plane and some on my legs... SUMBITCH, short short pattern, bring it in, put it on the trailer and go to scratching our nutts cause there is just no way in hell this can be happening.

A 3 hour call to Joe Grahek and now we have 4 people scratching nutts trying to figure this one out.

Joe calls me out of the blue a day later and said he had brain fart in the middle of the night.  The 532 was originally a points engine and he had converted it to CDI... You have to do some engineering to get the CDI conversion on it and he thinks that the timing may be off.  We pull the plugs and sure as shit, they are white / redish brown.  I bring the engine up to top dead center, roll it back to .070 BTDC and make some marks I can see with the engine running and hit it with a timing light... cant even see the marks in a 1" long window... DING DING DING I think we have a winner.  We have been chasing the wrong issue for about a year now.

Now we get to figure out how to modify the stator plate to get the timing reset to the proper specs.  Hopefully this will cure our problem and Greg will get to take a ride in his plane and start his training.

Will post more if this shit actually works :lol:

:beerchug:

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Posted

Gotta love the elusive two stroke or two smoke as the haters say.. in their defense there's a guy a few hangars down from me that's been trying to get a carbed 65hp continental to run for over a year.

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