Your my last chance before I have to pay BIG labour to sort this problem.

Okay after buying (now my third GTA)I noticed that once out of London, if I put my foot down the temp would rise very quick (see needle moving up!!) and to be honest the accelaration was slow, its seems all revs and no power. if driven steady temp stays about half way in slow or fast traffic.
since then I've disconnected the battery and have found that after doing so the car seems fine until about 20-30mins or until the temp reaches halfway mark, the car then slows down, no accelaration etc this goes on until I dissconnect the battery again.
Can anybody help!!!! being in the UK no garage wants to help or take on the job, which means a specialist i.e $100 per hour labour.
The car is a Pontiac Trans-am 5.7tpi GTA 1989, auto only other faults with the car is a leaking maniford gasket, otherwise VERY good original condition

 

Sounds like the lower air dam is missing...

Look for a vertical piece of black plastic about 15cm high all the way across the bottom of the radiator core support, immediately underneath the radiator. Without it, no cooling air is directed to the radiator at high speeds.

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"So many Mustangs, so little time..."
ICON Motorsports

 

There are several things to look for when this problem comes up.
Here's a check list for you.

1) Front Air Dam, located in the area described in the above post.

2) Lower radiator hose is collapsing. When the hose heats up, it may be caving in when you step on the gas. Get to car to proper temp and then have someone rev the gas hard while you watch the lower radiator hose.

3) Not the proper coolant mixture.
Do a system flush and add new coolant heeding proper mixure.

4) Radiator is clogged either externally or internally.
Check for debris on the front of the radiator. Check the flow on the inside of the radiator.

5) If your car has the electric fan..... The fan motor might be on it's way to the grave, replace the motor. They're around $30 US.

6) If your car has a clutch fan....
The clutch on your fan might be bad or going bad. Replace clutch fan.

7) Thermostat might be sticking.
Replace thermostat.

Those are seven things I can think of to check.

Running at 220° under normal conditions is no surprise and normal for the car unless you have made modifications to the cooling system.

Heating up when running the car hard is no real surprise either, but it should not overheat.
I'm thinking it might be your lower radiator hose.
It's not an expensive part to replace.

As for poor performance....
It could be many things.
You mention manifold leak.....
Is it the intake manifold or exhaust manifold??żż
If it's the intake manifold,
then too much air is getting into the engine and no gas to back it up.
Gives you high revs with no power behind the revs.

If I were you I'd go down to the autoparts store and get the following items.
Lower radiator hose, thermostat, 14 pound radiator cap, and 1 jug of anitfreeze. Do a system flush and take it for a spin to see if the problem remains.

Hope it helps or at least guides you in the right direction.

[This message has been edited by sunbitz (edited September 05, 2001).]