Heat Issuse

[nicmarshall46]

Hello everyone! I'm new to the group and looking for a little advice. I have a 98 m20m bravo and I am struggling to get good heat it is cold in the cabin with the cabin heat on full and the oat of -12c. I have had the shop look at it and we can't seem to find the issue. Please let me know if you have any thoughts on what could help or cause the lack of heat.

[kortopates]

Are you turning on the air too? This is a common complaint since most new owners don't realize the heat requires opening both Air and adding Heat by opening the Heat box valve in order to get heated air to flow. This is documented in your POH in the systems section.

[nicmarshall46]

34 minutes ago, kortopates said:

Are you turning on the air too? This is a common complaint since most new owners don't realize the heat requires opening both Air and adding Heat by opening the Heat box valve in order to get heated air to flow. This is documented in your POH in the systems section.

I have the cabin heat open and its luke warm if I open the cabin air it gets freezing.

[GeeBee]

Are you running ROP or LOP?

 

[LANCECASPER]

3 hours ago, nicmarshall46 said:

Hello everyone! I'm new to the group and looking for a little advice. I have a 98 m20m bravo and I am struggling to get good heat it is cold in the cabin with the cabin heat on full and the oat of -12c. I have had the shop look at it and we can't seem to find the issue. Please let me know if you have any thoughts on what could help or cause the lack of heat.

First of all, you live in North Dakota . . .  Minot, North Dakota at that.             "Why not Minot? Freezin' is the Reason" as you know, is a local saying up there. (I lived in GFK for 5.5 years and got my private there.)

That being said in the three Bravos that I owned (while living in Texas, not North Dakota, but occasoonally visiting Minnesota and flying at high altitudes) two of the three Bravos had adequate heat with cabin air mixed in. When I bought the third one in November 2015 the first thing I did was take out the old interior from 1993 to re-do. While it was out I added 5/8" Soundex insulation all throughout the cabin for noise. It didn't really do anything for noise but it did a lot for temperature, in the winter and summer.

Also in the extreme cold, you really appreciate an airtight door seal and baggage seal to keep out the 200 mph draft. Also next time you have the cowling off check all of the heater air hoses - they can disconnect pretty easily with all of the stuff crammed under there.

[carusoam]

Welcome aboard nic!
 

There are a few airflow studies, and temperature studies around here…

Start with a thermometer stuck in the air output and operate the heater controls…

Be sure to have a CO monitor in the cabin… not the dot… a real one.

 

High power, hot EGTs… generate heat…

Low power, deep ROP or deep LOP… generate less heat…

Leaks on the cabin make things uncomfortable in the depth of winter at altitude…

 

The heated air can get up to 180°F in some Mooneys…. Find @Shadrach for how he studied his heat system…

Air flow is a challenge to measure… in Long Bodies… it is pretty noticeable when you put your hand in front of it… 

Be on the look out for blocked hoses, or loose tubing… if the flow and temp don’t meet expectation…. While you are in there inspect the outside of the heater hardware… some people have put cameras up the exhaust pipe to have a look from the inside…

 

Another example…  an NA O360 in winter has difficulty putting out enough heat above 12k’… coats hats and blankets…. 

 

PP thoughts only, not a mechanic…

 

Best regards,

-a-

[nicmarshall46]

5 hours ago, GeeBee said:

Are you running ROP or LOP?

 

100 rop

[GeeBee]

Hmmmm, you should have heat. I asked, because I was in your area a while back out of KABR at pretty much the same conditions. At -11 I could not keep the cabin warm. I went from LOP to ROP and it made a huge difference. I would start looking for blockages and leaks. Have your shop pressurized the heat intake hose with a shop vac to see what your out flow in the cabin looks like?

[A64Pilot]

There are a lot of hoses, cables etc that penetrate the firewall, make sure they are all sealed as well as the foot boxes if that’s what they are called

[KB4]

Firewall fwd hoses old? Holes burned from exhaust?  After that inspection, remove Right seat, crawl under and check hoses.  Easy fix for these hoses.  Only the 2 defrost hoses are PITA.
 

On 1 hose, GeeBee sent wrong dia hose twice, so I ordered from these guys and it was half the cost. https://customductsaircraftsceetandscat.com/about-ducting/  Took 5 days for custom length. 

[tls pilot]

1 hour ago, KB4 said:

Firewall fwd hoses old? Holes burned from exhaust?  After that inspection, remove Right seat, crawl under and check hoses.  Easy fix for these hoses.  Only the 2 defrost hoses are PITA.
 

On 1 hose, GeeBee sent wrong dia hose twice, so I ordered from these guys and it was half the cost. https://customductsaircraftsceetandscat.com/about-ducting/  Took 5 days for custom length. 

What I can say is that Guy at Gee Bee has always been supportive, willing to go the extra mile, and has cost effective products.

I have dealt with Guy since early 1990s when he made up the first engine baffles for a Bravo.

The members on Mooney Space can shop any source they desire. Unfortunately as we all know, far too many sources do not have parts or no longer support our fleet. We should be thankful for those that continue to support us.

I am grateful to have sources that keep our Mooneys in the air.

[tls pilot]

23 hours ago, nicmarshall46 said:

Hello everyone! I'm new to the group and looking for a little advice. I have a 98 m20m bravo and I am struggling to get good heat it is cold in the cabin with the cabin heat on full and the oat of -12c. I have had the shop look at it and we can't seem to find the issue. Please let me know if you have any thoughts on what could help or cause the lack of heat.

In the early years of the TLS now Bravo, there was a cabin air modification

due to this mod, the heat was Not as effective

the key piece is figure 2, the butterfly assembly that due to this mod had four holes drilled thru it

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-255A.pdf

 

Certainly this can play a role but your duct flex tubing can really play a role

 

[KB4]

7 hours ago, GEE-BEE AEROPRODUCTS said:

We mfg per your dimensions and or advise the std lengths and I.d

Not for me you didn’t. I asked for 13” 2.5dia. Received 1 hose with different dia on each end and the replacement hose had correct dia but too long.  You said to cut to length which was impossible without exposing banding and eliminates the finished end.  
 

I didn’t have to trim anything and got exact size I ordered From these guys. 

https://customductsaircraftsceetandscat.com  

 

 

6 hours ago, tls pilot said:

[Guest]

The lack of heat in a Bravo is caused by the lack of heat exchanger area, it’s about half the size of the K model shown above. Second is the four 1/2” diameter holes in the cold air butterfly valve.  It is constantly diluting what little hot air comes from the engine.  Then add in a few leaks in the cabin, and you’ll be cold.

Clarence

[nicmarshall46]

22 hours ago, tls pilot said:

In the early years of the TLS now Bravo, there was a cabin air modification

due to this mod, the heat was Not as effective

the key piece is figure 2, the butterfly assembly that due to this mod had four holes drilled thru it

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-255A.pdf

 

Certainly this can play a role but your duct flex tubing can really play a role

 

So to fix the holes in the butterfly do you need to do the rest of the service bulletin? Or is it possible to just swap out the butterfly?

[Guest]

1 hour ago, nicmarshall46 said:

So to fix the holes in the butterfly do you need to do the rest of the service bulletin? Or is it possible to just swap out the butterfly?

The original butterfly valve didn’t have the holes.  You can tape the holes closed with some foil tape to see if it improved your heating.  Acclaims had an “improved” heating system which had you drill a 3/4” hole in the left cabin air scoop.  It allowed a jet of ice cold air to blow into the cabin above the pilots left knee.  
 

Clarence

[carusoam]

In the other long bodies….

The holes in the cold air butterfly are there for a reason….

They bleed in enough air, to keep the system from overheating if the cold air is completely turned off…

The hot air can get really hot if not diluted…. (Other planes…)

 

Sooo…. un-dilute carefully….  
 

PP thoughts only, not a mechanic…

Best regards,

-a-