Ok so I was driving my car one day and noticed the coolant light was flashing so I pull over and check it out. I check the coolant and there was oil in it. I limp it home and start working on it. I changed the headgasket, waterpump, timing belt and drive belts. I drove it the next night and everything seemed fine. I went to drive it to work the next day and it started to overheat (btw I live in Houston so it's really hot during the day). So I investigate and find that there is still oil in the coolant. I changed the oil cooler, flush, fill and bleed the coolant system. I also changed the oil to make sure no coolant got into the oil which it didn't. I drove it at night (not as hot as the day but still high 70's low 80's) and it did not over heat.

The next day I drove it and it overheated again but I noticed the heat wasn't working. So I flush the heater core, check the Tstat with boiling water to make sure it was opening, flush, fill and bleed again. It is still overheating. The only thing I can think of at this point is the radiator. Is it possible that the oil has clogged it? When I flush the radiator the water seemed to flow through it freely.

Things to note:

New water pump
Thermostat checked out
The top radiator hose will be scorching hot, but the bottom one is barely warm.
I am using just water at this point to save money while diagnosing the problem.

 

What kind of coolant had been in it?

 

Maybe theres a crack in the block and oil and coolant is mixing, how does your oil look at this point?

 

Green coolant but it was not mixed with G12. Currently it just has water in it so I can try to figure out the problem. Once fixed I'll refill with G12.


The oil is still good. I've test driven it a few times today and it overheated. When I pulled off the radiator hoses I found some oil still in there but I checked the oil level and it has not gone down. I think it may have just been some oil still in the system somewhere. The oil seems to just coat the pipes so it's hard to get it all out.

At any rate, even if there is a bit of oil in the coolant it should not overheat that quickly. Another interesting note is that the temp stayed at normal until I turned on the A/C than it instantly started to overheat.

I also checked the radiator and noticed the top was hot but the bottom was still cold.

 

IF your thermostat is find then sounds like a huge air bubble. i dont know what the side effects of green coolant are and how long it was in there but its usually not good. Have you changed the head gasket or checked the oil cooler? they are the main reasons for oil in the coolant.

 

Your thermostat isn't opening. I'm wondering whether you bled/blew a big air bubble out of the heater core, for example, and into the main cooling pathway, which is blocking the thermostat. Have you tried burping the system recently? I'd do that and see if it helps.

 

Also, you can drive with the coolant cap off so that the system doesn't pressurize - that'll help the car stay cool if it heats up on you while driving - it'll get you home.

 

I've moving the heater hose and filling it with water til water comes out of the hole in the heater hose. To burp it I just need to run the car without the cap on and have the heater on correct?

 

Well I got it fixed, I drove in 100* heat with the A/C on and it stayed at normal. I ended up burping it a couple times and that fixed it apparently. Thanks for the help