Hey guys, so after a long car ride my car started over heating and dieseled when I went to shut it off. Any time the car goes over 220 it will diesel when I shut off the ignition and have to turn it off by pulling the fuel pump fuse. I've replaced the radiator, thermostat(195), water pump, upper and lower hoses, radiator cap, coolant temp sensor, coolant temp sender, and am using a 60/40 water coolant mix. The 305 has 160xxx miles on it and is showing signs of a worseninghead gasket(white smoke on start up). Is it possible the head gasket is causing these problems or am I overlooking something?

 

The fan is coming on and is wired to the ignition by the previous owner

 

Try checking the Timing and use High Test Fuel.

 

I'll have to take my timing light out of storage, it might be difficult cause my timing marks look pretty banged up

 

Wow, looks like you've covered everything. How is your air dam? the plastic piece below the radiator that forces air into the radiator fins while driving. They get torn up and if missing will create an overheating problem. Also check to see if your radiator cap is truly holding pressure. I'm sure you cleaned out the leaves and junk that gets caught between the ac condenser and radiator when you replaced it.Sounds like the fans working correctly. Can you feel water in both the lower and upper rad hoses? Have you tested the thermostat? Boil some water in a pan on the stove hold the stat with a pliers and place it in the water, you should see it open. Cont

 

I'm not 100% sure if its possible but if combustion heat is getting past the head gasket into the water jacket there is no way for your cooling system to remove that kind of heat. Clogged new radiator? If you open the small pet **** and the coolant should flow out quickly. Sorry, that's all I've got, maybe someone has some good info for you on the head gasket. Good Luck.
Sincerely,
Roy

 

I just put a 180 degree thermostat in and the car hasn't gone over 220 since but it will stay at the line directly under after a good 30 minute drive. There was a lot of leaves between the condenser and radiator lol. The cap seems to hold pressure well but when I bought it I wasn't too happy with how easy it twists on and off. I'm thinking about trying out a 170 degree thermostat to make it run a little cooler. any thoughts on that?

Oh yeah and the air dam is in good working order

 

I was wondering if an old head gasket could have that type of effect on coolant temp, hopefully someone can answer that. The radiator flows fine. Thanks man

 

Tyler, I had a similar problem years ago and it was the cap! The car would not over heat to any large degree but would diesel/run on at shut down, drove me crazy until I changed the cap, make sure you get the correct pressure. I run a 160 stat but do not have any computer control of the engine except the trans lockup. I built a 350/.060 over 4 bolt from scratch with forged internals etc. I have a large aluminum radiator and AC and it runs about 170 in traffic with the AC on....all good. Your engine needs prob. close to the 195 to put it in the closed loop operation, not sure, but for all those wonderful smog components etc to work as designed it needs a higher temp for the computer to do as designed. Running a cooler stat wont kill you but the engine won't operate as efficiently. Just for grins try a new cap, different manufacture than your current one. I've always run a 160 stat but after removing all smog stuff/computer input. Good luck/Roy

 

You need the right parts to satisfy the ECM