Let me start with we have tried just about everthing. Of course not everthing because it still overheats.

What I have replaced:
1.)Radiator *new {1 1/2 years ago}
2.)Performance Cooling Fan "black magic"
3.)305 tbi-350 tbi
4.)Almost 10 thermastats at many different temp.
5.)The black plastic thing underneath the car
6.)Replaced the water pump several times

What I have done:
1.)power purged the cooling system
2.)checked coolant mixture
3.)check for anything blocking the radiator like bags and ect....
4.)Checked the timing with the local shop several times
5.)checked the gauges accuracy with laser temp gauge..

Now i will expain what it does:

Usually it only over heats with ac on. When I first start the car it starts to get hot about 240 then drops. Then after driving for a while in 90-100f weather it starts to get hotter and hotter until it gets to the red. Usually while driving in the city. But every now in then like this morning it snuck up and pegged out on me on the toll road at 50-60mph (temperature gauge that is). But that isn't normal. I am really lost and have no clue what to do now. Even before we replaced the motor it overheated. The timing has been adjusted by a local automotive shop several times. Can someone plz help???

[This message has been edited by python8 (edited August 20, 2001).]

[This message has been edited by python8 (edited August 20, 2001).]

 

I own an 84 TA 4bbl HO. You sound like you are suffering from a similar problem that I just had. I normally drove my car around in the city, and it would go well past the half way mark, and up to the red. Especially when pulling hills. From time to time, it would drop from almost RED to the mid-line, then climb back up again. Then I took it for a long ride on the high way, and the temp went through the roof, and I spent the better part of the day waiting for the engine to cool down. To make a long story short... the THERMOSTAT stuck. I took it out, and the temp hardly climbs... even when I'm pulling hills at high RPM... it will go to the line past the half way mark, then drop shrotly there after. So, check that... if you don't know where it is, look for where the TOP hose from the Radiator comes into the intake manifold. It's right in that goose-neck piece of metal. I'm guessing it might be that also because you didn't list it as something you've changed or done. Hope this helps.

PS... you might want to replace it before winter... if you want your car to have heat and warm up at all. But, driving it around for the rest of the summer should be fine.

 

I had the exact same issue and did everything you did. But purging the system and a new cooling temperature sensor solved my problems. But since it seems to be getting hot at higher speeds, I wonder if the hoses are collapsing? Were they replaced?



------------------
Kiss_My_SS
1992 Camaro RS/Heritage Package
1996 Impala SS
1985 Good ol' Chevy 4x4 Truck

 

Well, you've done several things to the cooling system, but I'm wondering if they were done right?

You mention a new fan for the rad.
Is this a pusher fan or a puller fan? Is the fan mounted to the front or back of the rad?

If it's a pusher fan and you have it mounted to the back of the rad then there's your problem right there.

If it's not the fan then I's have to side with SS and check your hoses.

It could also be a faulty T-stat, but I don't think so at this point.

Do some simple tests.....
1) check to see #1 that the fan is in fact coming on, #2 is the fan blowing back towards the engine or towards the radiator.

2) You'll need a buddy to help you with this one.
Pop the hood and take the rad cap off. Have your buddy start the car while you keep an eye on the rad filler opening. Once the engine gets warm enough for the t-stat to open you should see the water level drop a bit and moving. Have your buddy rev the engine a few times to see if water is flowing through the rad.
This will tell you two things. #1 the t-stat is opening up and your water pump is working.

3) Stop the engine and replace the cap. Start the engine again and rev it several times while keeping an eye on the lower rad hose. Is it collapsing?

4) Is the car truly overheating or is it a faulty gauge or temp sending unit.

Is this new rad a single row with a plastic core? Could have gone through meltdown and the rad is not flowing like it should.
What is the condition of the water both now and then.
If you had real nasty/rusty water prior to the engine swap etc. You may have transferred that over to the new system.

Just some thoughts.
Hope it helps.

 

try replacing the radiator cap.
some people have solved their overheating problem this way...