I'm hoping some of you can help me with a problem, I'm not sure what the cause is.

My brother has a 91 Firebird w/305 an auto trans. The car is in great shape, with about 75k miles. We recently did some maintenance work on it: changed plugs, wires, distributor cap/rotor, fuel filter, thermostat and flushed the radiator (flushed for the first time since the car was new ).

Prior to doing this work, the car ran fine, but you could tell was a little lazy with the power. After doing this work, the car got hot (about 225), while in line at a drive-through. It had never ran that hot before. At the same time, white smoke was visible from the exhaust. This started after about 100 miles of normal highway driving.

Suspecting a blockage in the cooling system, I re-inspected the radiator and it was still quite brown even after the initial flush, which took about 20 minutes. Suspecting the radiator might be clogged, I pulled it from the car and ran water into it while shaking and rotating it - alot of crap was in there.

After putting it all back together, there was no change.

The car can idle for a long time without getting up into the 220's, but it will smoke out the exhaust. If you drive it, it'll get hot after about 10 minutes. It'll run great, doesn't shake or seem to have lost any power.

One thing I noticed is that the heater no longer works, but it worked prior to the initial flushing. If I turn it on when the car is approaching the 220's, it'll drop the temp down back into the 160's.

Based on the smoke and the overheating, I'm suspecting it is a blown head gasket, but with it running fine and the heater thing, I'm not 100% sure.

I changed the thermostat again thinking it may have been stuck but no change. The water pump seems to be working fine as you can see the water flowing in the radiator with the cap off.

Plug gaps were set correctly and the wires were routed properly. There is no sign of water in the oil, but the radiator water is still turd brown.

Any thoughts?

 

Does it blow white out the exhaust all of the time? Use or loose anti-freeze? If so, I too would suspect a head gasket. If the oil turns to milk shake brown or you start to see water on the dip stick you'll know for sure. Same can be said for the coolant.

Or, does it just puff white greasy smoke when re-started?

If you're not loosing or using coolant and it's just bad brown, it might be that the years and layers of built up rust and corrosion are circulating and were not properly flushed. Did you pull the block drain plugs and flush the block? It'll be hard to get throughly clean if it was neglected for years.

225 isnt too hot for these motors. GM designed them to run hot, cut down on the bad tail pipe emmissions. That can be changed but, that's another topic.

Keep an eye on the dip stick and coolant levels. That'll be your clue.

Good luck

 

as far as keeping temp down goes, a product called redline has worked wonders for me. i think its somewhere around $10 or something and you can add it to you antifreeze. my mustang used to run a little hot (not overheat, but a little hot) and now after adding it, it runs a little on the cool side of the guage which makes me feel a little better. that may not be the whole solution to the problem, but you never know.

that sounds like it could be a blown head gasket pending on the answers to wade's questions.

 

I believe it does blow white smoke all of the time yes. While idling in the driveway, it is clearly visible, but when driving, I can't really see it in the rearview mirror. I am pretty sure it does smoke while driving too.

I just checked the water in the radiator and it is milkshake brown, but I remember it looking this way just a couple of days after the initial flushing and it is how it looked prior to me doing any work.

The dipstick looks perfect.

It does appear to be loosing coolant, and no leaks were visible. Where are the block drain plugs - do you mean the brass plugs? I would like to try this, but have no idea where they are.

Here's a question. Could a blockage in the cooling passages of the engine block be causing coolant to build pressure and be forced to blow out the exhaust?

thanks for your help.

 

That's what I am afraid of.

If it is a blown head gasket, could I just swap in a new one or do you think headwork would also be needed? The car runs great otherwise.

 

pull the plugs one at atime and look at them if you have one thats really clean(looks new) you have a blown head gasket.the coolant will clean all deposits on the plug ,hence being very clean.later jimmy

 

Sorry for the bump but hoping someone can help me locate the engine block drain plugs that Wade mentioned. thanks!