How about these baffles?

[Gwt9678]

Hi All,

In the quest to keep my oil temp in my 0-300 powered 172 in check on these 100 degree days, I took a good look at my baffling today and noticed a couple things. Pictures are attached here to show what I'm looking at as best I could get them with my phone stuck inside the cowl. On the pilot's side, I see a couple small folds and one beam that appears to be pushing down on the baffles, preventing a seal. On the co-pilots side, I have about a 1/4" gap running along the corner of the cowling. Are these gaps worth looking into? I've also attached a photo of my air filter box, as it has about a 1/2" gap all around it that I'm thinking may be putting higher pressure into the bottom cowl. Would you take the time to re-do any of these?

 

[kyleb]

Every baffle leak is worth repairing. In the location where the baffle seal is hitting the stiffener, I'd slit the baffle material so it nests around the stiffener. There should be a wear mark on the seal to show you where to cut.

In the area where you think there is a 1/4" gap, look to see if the baffle seal is evenly worn on the cowling side, indicating a decent seal. If not, you need to install (or have your IA) install a new piece that effectively closes the gap. A 6" x 1/4" gap lets a lot of air escape with no benefit to cooling.

The other thing to do is seal any gaps between the baffles with RTV.

 

[Bill Watson]

Every baffle leak is worth repairing. In the location where the baffle seal is hitting the stiffener, I'd slit the baffle material so it nests around the stiffener. There should be a wear mark on the seal to show you where to cut.

In the area where you think there is a 1/4" gap, look to see if the baffle seal is evenly worn on the cowling side, indicating a decent seal. If not, you need to install (or have your IA) install a new piece that effectively closes the gap. A 6" x 1/4" gap lets a lot of air escape with no benefit to cooling.

The other thing to do is seal any gaps between the baffles with RTV.

I was thinking the same.

Some experimental types use a lot more RTV than I typically see on certified equipment. I think you can do a lot with it but it can look messy.

If you ever have it redone, consider silicone baffle material if that’s an option. Seems to work better all around.


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[bnt83]

I've seen 135 piston operators buy red RTV in the caulk gun tubes, YMMV.

 

[Ted]

I would redo those baffles with new material. Those scallops and the 1/4" gap are hurting you. Then go through with a tube of red RTV and fill in every gap you can find.

I did this on the 310 and the 414 and temps went down immensely.

 

[Bill Watson]

I've seen 135 piston operators buy red RTV in the caulk gun tubes, YMMV.

Yes, caulk tube gun assumed. It’s hard to avoid creating a bit of mess but it works.


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[Let'sgoflying!]

Its possible that in flight the 1/4" gap is sealing as the wind load pushes on it.
However, not a bad idea to replace it so it is always sealing. Feel of them. If stiff; it's time.
What oil temps are you seeing? What oil are you using?

 

[MooneyDriver78]

I’m thinking that maybe the naked rivets are part of the problem?

Tom

 

[Dan Thomas]

Hi All,

In the quest to keep my oil temp in my 0-300 powered 172 in check on these 100 degree days, I took a good look at my baffling today and noticed a couple things. Pictures are attached here to show what I'm looking at as best I could get them with my phone stuck inside the cowl. On the pilot's side, I see a couple small folds and one beam that appears to be pushing down on the baffles, preventing a seal. On the co-pilots side, I have about a 1/4" gap running along the corner of the cowling. Are these gaps worth looking into? I've also attached a photo of my air filter box, as it has about a 1/2" gap all around it that I'm thinking may be putting higher pressure into the bottom cowl. Would you take the time to re-do any of these?

The picture of the curved baffle away from the top cowl indicates a poor seal fit. The installer curved the seal too much and it can't contact well, even with air pressure on it.

Slitting the seals at the stiffeners can help, but realize that the engine shakes and moves when it's running, and it can rip those seals and damage the cowl at those spots as the slitted seal tries to stay locked on the stiffener.

RTV can make a mess and get between the fins and make things hotter yet. It can also break away and let small bits get into the carb heater inlet and end up in the carb, causing some real trouble, like engine failure.

We need some photos of the engine with the cowling off it. There are intercylinder baffles that I have sometimes found missing, letting a lot of air escape without doing any cooling, and such a leak also reduces the pressure differential between the top and bottom of the engine, slowing the cooling air and letting the engine heat up.

Don't forget the seals at the front of the engine. They can be in bad shape (or missing) and let a lot of air escape.

The induction filter seal (to close off the half-inch gap around the filter) was introduced in the 172 around 1970. It wasn't part of the type design before that, so it wasn't legally required, but it is required for those models that came with it. They're often missing or busted all up and they let air in there that wrecks the pressure differential and lets the engine heat up. It might be a minor mod to install one on yours, but the Cessna seal is a bank-breaker in cost. And it's cheap plastic. Dynamic Propeller makes a fiberglass version that is much stronger and cheaper. http://www.dynamicpropeller.com/untitled.html