I am about to order some 4-6mm adapters for a vacuum hose job and was wondering what temperature rating they need to be spec'ed for. I suspect that the plastic Pep Boys adapters will not do the trick. Found lots of threads on underhood temperatures and reducing them but no actual temperatures. Anybody have actual numbers. I used to have a probe that I could use to measure it but lost it in a move.

 

Don't know the temp, but it get's very hot. When I did my vacuum hoses over, all of them were rock hard.. When I had my friend repaint my car, my hood was warped from the heat. Bought a Scoot replica to help ventilate the bay.

 

I don't know for sure, but I would think 400 degrees minimum.

 

I don't know.... 400 F. sounds a little high to me, but I guess it would depend alot on where your measuring the air temp.
I've got a wrapped DP but with all the stock underhood plastic and a stock hood. I haven't ever bothered to measure, but after a typical drive on an 80 deg day, the UIM and other metal parts (excepting the turbos obviously) are hot underneath the hood, but I can still touch them, if only briefly.

 

I agree, 400 is a little high. I'll take some readings of various components with my infrared thermometer and post them. I have a fairly empty engine bay and a mazdaspeed hood so YMMV.

 

Would be interesting to see these numbers. However, I was wondering what the ambient underhood temperatures were. Obviously, they would also vary a lot depending on underhood location.

 

Your under hood temps are going to be well in excess of 230 degrees at times. On a hot day your coolant temps can approach 230 degrees. Your coolant acts to cool engine parts that are hotter than that. Some parts of the engine probably get close to 300 degrees, and that doesn't count the turbos or exhaust.

 

I went out for a little drive tonight and took a few measurements.

This is nothing scientific as I didn't record environmental data and my IR thermometer isn't a very nice one. It was probably about 80f ambient temp though, normal city driving, PFC fans set to come on at or around 90c. The hottest part that I could get to was the top of the primary turbo cartridge area at 395f. The primary compressor housing was about 200f. The UIM was around 114 when I shut off the car and crept up to about 140 after only a couple of minutes. I measured the filler neck to get an idea of the accuracy of my IR thermo, and it was roughly what I would expect at 195f. Take these numbers with a grain of salt, but it at least gives and idea.

 

Yes, but radiant heat beyond a couple of inches never reaches close to those points unless the car has been sitting motionless with the hood closed (and even then, once the parts stop dealing with combustion, they begin to cool as well, albeit slowly). The coolant may be that hot, but it doesn't heat up the ambient temps to that same point, as it's shedding the heat into a far larger space. The surface temps may be that hot, but it takes some serious insulation to hold any of that heat; more so than just the hood and its sound insulation.