Overheating

[c_fergy137]

hello i have a 85 302. when im driving down the road and i cut my a/c on my oil pressure gauge goes to just below the jigh mark and my water temp gauge goes up and down. i have changed my fan clutch sprayed off my radiator and adjusted my timing wiht no change anybody have any clues to what this could mean. tongiht i parked my truck popped the hood and turn the ac on hihg to see what would happen. and the same stuff happened it ran for about 20 mins then i shut it off looked under hood and could hear a hissing sound from where all the a/c equipment is located. thakns chris

 

[crazyhorse85]

The hissing sound your hearing is just freon pressure bleeding off....That is what your compressor is for it pressurize's the a/c system...Your gauge problem could be anything form a problem in the harness or as simple as just a sensor or sending unit....On yor temp gauge have you replaced your thermostat???I've noticed on some of my buddies truck that you can just about watch the gauge an tell when the t-stat opens cause the gauge needle will drop...Just something to think about...Hope it helps.... B)

 

[92broncomann]

c_Fergy137

How does the a/c run? is it cold? or ok? When you turn it on, does it come on automatically or does it take a bit to come on.

92BM

 

[50joe]

This is only when the A/C is on? Does it have to warm up for the temp to fluxuate, or does it even when cold? I'm thinking electrical more than mechanical problems, so you might want to start checking ALL the ground wires going to the engine.

 

[muddrivermike]

Ahh,,,Its almost winter time,You can ignore it till summer,,HAHA.Anyway Mine does something like that.When I turn on the ac 2 things happen,,1st is the engine rpms drop a little which can change what your oil psi is reading cause the engine is turning a little slower,2nd my temp goes up a little,either because its an extra load on my engine or probably because I dont have a fan shroud on yet.But this only happens at idle.At any speed moving I dont notice it.So far its never overheated or had any problems.

 

[50joe]

This brings a great poinnt. The a/c on creates a greater load on the engine, and changes alot of factors. On my 96, it does drag the lil 302 a bit, and does increase the engine temp a tad, but shouldn't make an instant jump. If it does, i'm going to say a ground problem, if it takes a bit, gonna go with mechanical.

 

[50joe]

Nothing in the original post indicates overheating.
Neither did any of the responses