Buckaroo

Friend with Rans has high CHT today question?

18 posts in this topic

My buddy today had to call off a trip today due to high CHT. While cruising his CHT got close to the red and when he powered back some it got worse. They managed to get home alright. 

He's saying he thinks it's from the Costco gas he just put in saying sometimes the drivers screw up the batch. 

They just flew in from Texas 4 days ago just fine.

Any thoughts? It's a 912 uls.

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Update! After draining Costco gas and running 100LL the CHT is still hotter than normal. 

Water cap problem??

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It wasn't a fuel problem. It is a coolant issue. It's either low coolant level in the expansion tank (not the reservoir) or a slightly reduced radius hose. A water pump issue is very rare. If he is using Evans coolant that is the problem. Dump it and use 50/50 mix.

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1 hour ago, Buckaroo said:

Update! After draining Costco gas and running 100LL the CHT is still hotter than normal. 

Water cap problem??

I had a similar experience , and in my case, it ended up being a sensor problem.

Cheers

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My vote is a indication sensor error, possibly caused by a bad ground. That being said it needs fixed, whether it is a real cooling issue or a indication issue.

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I passed these opinions to him. Thanks for them! 

He ordered a new coolant cap shipped next day. He wants to rule that out! Opinions good or bad welcome! I'm lending him mine in the morning to see what happens ups is late in the day.

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The VDO cht sensors use, in my opinion a crappy connection. I'd personally rather have seen one of their sensors with the little stud and nut. Check there for a bad connection, it can get some grime there and give issues. I run two CHT gauges to help rule out those kind of issues and it helped once when I had a iffy connection there.

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They went in and removed the thermostat put it in boiling water and it was stuck. With no part availablity here they removed the thermostat entirely and button things up. I had to leave so I don't know the outcome. 

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The CTSW typically doesn't have a coolant thermostat, but the CTLS does. I had a customer airplane have one stick. It would overheat before you could get it into the air.

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That's good news as one less thing to go wrong! I don't know if removal of the stat corrected things yet. It's reaching 100 degrees here so mechanical things tend to want to fail now if there on the verge. 

Next step will be the sensor.🤞🏿

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The CTSW folks with thermostats seem to get more trouble than benefit from them.  Just an observation from what I see on this and other forums.

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26 minutes ago, FlyingMonkey said:

The CTSW folks with thermostats seem to get more trouble than benefit from them.  Just an observation from what I see on this and other forums.

Is there a easy way to tell if mine has one?

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SW's don't have them. Only LS's. 

I personally don't care for the oil or coolant thermostats. 3 qts. Of coolant or a 3 liter dry sump just isn't worth it. A 2" wide strip of tape works just fine and no extra failure points, no extra at hose change and they are just in the way.

Ford's and Chevy's.

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The Rans man fixed the CHT problem by ripping out thermostat. Then he goes for a test run and experiences a stumble at 3700 rpm followed by a smooth out. He's running a 80 hp Rotax with a 914 kit and turbo on his Rans. Now he's stymied as to the stumble. We'll remember when the CHT's got hot and he ran 100ll thinking he got low octane Mogas? According to Mark Pringle the 100ll released something in the carbs which was clogging something in the carbs. The cure recommended by Pringle was to run some Seafoam through her. By golly it worked and she's smooth as silk now! 

Im going to run some Seafoam in mine just to clean the system some. I hope it doesn't release a carb massive piece of dirt and block things!🤔🤔

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Seafoam didn't cure anything for a stumble. Just coincidental timing. If it runs smooth then let him believe. All is good when things run smooth.

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1 hour ago, Roger Lee said:

Seafoam didn't cure anything for a stumble. Just coincidental timing. If it runs smooth then let him believe. All is good when things run smooth.

Yes, I've kinda wondered about this whole sequence of events! In this whole episode it seems voodoo fixes have prevailed! This to me is a nightmare as there are no definite causes to the situation just temporary feel good fixes! 

I'm happy for my bone stock 912 ULS! I'm not interested in Turbos anything at this time! 

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Lots of folks swear by Seafoam and Marvel Mystery Oil.  They might both be the best things since boobs and ice cream, but I'd be very cautious about putting chemicals not recommend by the manufacturer into a nearly $20,000 engine...

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Seafoam is largely naptha with a couple detergents. It's all petroleum based.

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