I have a 1970 FJ40, original F engine, most everything is original as far as I know. Aftermarket temperature gauge, normally operates around 180-200 deg F. Once it gets above 200, you can tell the thermostat opens and brings the temp back down. Have had it this way for over 10 years without noticing really any abnormalities. I have driven it a couple times a month for the past 2 ish years with surprisingly no major issues. The other day I took it out and it started running very hot. Stayed around 220-230. Then I noticed the brakes were feeling pretty stiff. Stopped at Buc-ee's for a bit, then took her home. Brakes very stiff and still running hot on the drive home. Brakes were not pulling to one side, just stiff. I could stop, it just required much more force than normal and felt like there was no vacuum boost. For reference, all brake wheel cylinders were replaced a couple years ago and have given me no trouble at all since.
I found it very strange that these two seemingly unrelated systems failed at the same time after all this time. There is only one connection between the engine and brakes that I can think of: the vacuum line from the intake manifold to the brake booster. My thinking is that if the booster diaphragm is torn, obviously I won't have any brake boost and the pedal will feel stiff, as if the car is off. Also, ambient air would be leaking into the intake manifold through the brake booster. I understand if this would cause rough idle or bogging down. Is it possible this could cause overheating, too? I understand there is some correlation with A/F ratio and overheating, but for some reason it would surprise me if a vacuum leak would cause such a large increase in temperature.
I'm open to hearing what else y'all think this might be caused by! I suppose they could be caused by unrelated things, the timing was just too perfect for me to think that is likely.
I found it very strange that these two seemingly unrelated systems failed at the same time after all this time. There is only one connection between the engine and brakes that I can think of: the vacuum line from the intake manifold to the brake booster. My thinking is that if the booster diaphragm is torn, obviously I won't have any brake boost and the pedal will feel stiff, as if the car is off. Also, ambient air would be leaking into the intake manifold through the brake booster. I understand if this would cause rough idle or bogging down. Is it possible this could cause overheating, too? I understand there is some correlation with A/F ratio and overheating, but for some reason it would surprise me if a vacuum leak would cause such a large increase in temperature.
I'm open to hearing what else y'all think this might be caused by! I suppose they could be caused by unrelated things, the timing was just too perfect for me to think that is likely.
