Hey everyone.

I was pretty sure on my last topic on this that I rectified the issue. I bought a new radiator cap (which is a tad loose?) To touch base, here's all that has been done before this:
New radiator
New wp
New thermostat (lower temp )
New cap
New gaskets

I have checked the oil and it looks clean (changed it about 500 miles ago) so it is hard to tell. Also there is blow by on start up but I'm pretty sure it is just oil, because I need to add a quart once in between every oil change.

Going back to az to do something about that cap. Its doesn't require pressure to release it like the original (which had a gash in the gasket and the spring didn't work)

Any other things to check? Haven't pulled plugs yet but it idles like new and drives really smooth

 

If there's no external leak then there's only a couple of options. Bad head gasket allowing coolant into the cylinders to be pushed out the exhaust. Possible cracked head doing the same thing. Bad intake manifold gasket allowing coolant into the lifter valley but you say the oil isn't contaminated.

A bad head gasket can be discovered if the cooling system gets over pressurized from cylinder pressure. First indication is lots of bubbles in the coolant.

One other possibility is a leaking heater core. Check under the matting on the passenger side floor to see if it's wet.

 

It does only lose small amounts of coolant. After about a month or two I only added maybe a quart of coolant.

I will pressure check it. I do hear bubbling when I shut the car off but sounds like it comes from the rear. I will take it out for a spin and check it. Also I didn't see any signs of a leaking heater core.

I went ahead and purchased a used original radiator cap first since I feel like this aftermarket is letting steam out. My original one was always on so tight. This one, no matter how pressurized the system is, it doesn't take any pressure to turn it

 

Ran my hand under the kick panel passenger side and finger end with muc . Found the leak!

 

There you go, bad heater core!

 

Enjoy THAT R/R!

sarcasm

 

no doubt. I always love being upside down working on my head under the dash....

 

it's much easier in the firebird. 30 minutes tops.

 

Not doubting ya naf, but when I changed one in a 85 T/A, I'm pretty sure it was longer than a half hour.

Please share your technique

 

You can remove a relay bracket and gain immediate access to the top bolt for the heater core cover, unlike the camaro that requires more extensive effort.

Did my 85 last Fall. Was prepared for some work and was pleasantly surprised. I was done, with new heater hoses in less than a half hour.

 

THAT is good to know naf! I did that 85 in 1987, No forums and a hellava lot younger! I can be at ease now when it comes time for the 88 and 89.
Thanks