Overheating on the highway. 76, 2.0 Options

[SVG223]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

[mgphoto]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

Does the engine have a catalytic converter? Clogged converter will create back pressure causing overheating. ‘76 my in California had them.

[SVG223]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

Does the engine have a catalytic converter? Clogged converter will create back pressure causing overheating. ‘76 my in California had them.

Yes, it does. I found a receipt where it was replaced in 2005 or so in California.
I wouldn't mind being rid of it. I'm not sure how to check the back pressure.

[wonkipop]

My 914 overheats on the highway. I had concerns about the air flap, but I think the thermostat has broken and it stays in the open position. I thought something might be clogging the fan but it looks clear. I wonder about the heater air hose that goes over the motor. It could be blocking some air possibly. I may try to tie it out of the way. After exiting the highway and stopping at a stopsign the idle was extremely low, I was surprised it was still running. I turned the engine off for a while and it ran better after it cooled down. Any ideas would be appreciated.

Does the engine have a catalytic converter? Clogged converter will create back pressure causing overheating. ‘76 my in California had them.

Yes, it does. I found a receipt where it was replaced in 2005 or so in California.
I wouldn't mind being rid of it. I'm not sure how to check the back pressure.

probably not easy to check exhaust back pressure on 914 of that vintage.
modern cars you plug into 02 sensor in front of cat.
someone on this site might know how to do it if sensor plug in not available.
your mechanic may even know how to.

a couple of weeks ago one of our circle brought his wife's audi into the workshop.
it wouldn't make power properly past idle and it was running slightly hot.
turned out the cat had spat a piece from inside which is like a ring or pipe connector and this had turned sideways in the outlet pipe and was blocking it.
cat was not that old either, but it was an aftermarket cat.

you might be able to get the cat off to inspect it visually.
likely to be a pain in the a with stubborn nuts.
your mechanic could do it.