Hi,
Have a slow to moderate coolant leak. White smoke coming out exhuast. Low coolant light, have to keep refilling periodically. Will only see smoke at idle, when normal driving you will see none. Car maintains its temperature around 180-185. Just changed the head gaskets thinking it was it, also have a new water pump on there, like 2 weeks old new. Oil is not of milky color, nor is coolant.
Radiator.... was changed in 2006 at 100k mark or so, car now has 136k on it? Any thoughts....

Have a:
1996 Corvette, LT1 with 401 in it

 

White smoke coming out of the exhaust is the sign the engine is burning coolant. If it is not leaking at the head gaskets then other alternatives are cracked head or block.

Is it white smoke or just steam from when you start the car and the exhaust heats up, which can happen for the first 20 minutes or so?

 

It is only noticeable at idle, it continues even as I drive. So u drive, see nothibg, stop see.smoke, dissapates.about 4ft.ftom.car. And this occurs throught driving.

 

Sounds like a head gasget to me

 

Check your plugs. One might be clean an white. Do a leakdown in this cylinder. Check for bubbles in the radiator when the cylinder is pressurized.

 

jake, look at my cyl #6 plug...it was steem cleaned do to a blown head gasket. This might be an inspection to conceder.

 

Just put brand new plugs in on Sunday. Guess that was yesterday, ill pull them and check. I'm losing my mind on this car, if its not one thing its another. I just finished changing head gaskets Saturday to.

 

How far did you drive it ? If coolant got into the exhaust system when you pulled the heads, it takes a long time to burn out. On three different occasions I seen it take 20 - 30 minutes for the steam to stop coming from the tailpipes.

 

Did you just swap the head gaskets? You need to always check (or have checked) the head for flatness as well. 9 times out of 10, they need to have a little surfacing done to them so that they're flat. If you don't do that....the new head gaskets won't seal.

What heads are you running? When you have a troublesome leak like this, it's always good to have the heads pressure checked. Aluminum heads can crack and not leak coolant when the engine is cold. Once the the engine is running...which causes heat....which cause aluminum to expand...coolant leaks from the crack.

 

Some good suggestions above, another possibility is a hole into a coolant passage if the heads have been ported, best wishes for it to be something else.

 

If you wanna know for sure, pick up a test. There is a video on Youtube that describes the test and what it's called and where to get one. Basically it involves a tube that attaches to the radiator and a chemical that reacts with exshaust emmissions in the coolant. If the chemical turns blue, it's the gasget. Or the head itself and so on......You seem to obviously have a real problem on your hands and I agree with having those heads decked, especially if the're aluminum.

 

In reply to 96GS. They are aluminum Dart Pro 1 180cc. I did not have them checked, or decked once i pulled them. Also the smoke does increase as the engine gets warmer and warmer. Heads have not been ported. Oil is now becoming contaminated with coolant as well. Contemplating if it is the heads or block..... seems everyone is pointing to heads right now.

 

Look at it this way...regardless of if it's the heads or the block, the heads have to come off and they need to be checked. If the heads check out bad...you have your answer. If the heads are flat and check out good...you have your answer.

The only way it's the block is if the surface prep was somehow messed up or there was a large piece of debris under the head gasket when you laid the gasket on the block.

 

may I suggest something possibly overlooked ? are you running coolant through the stock throttle body ? try bypassing the coolant around the throttle body; either cobble it together yourself or use one of those $20 bypass kits almost every corvette parts place sells. let's hope it's something simple.

 

If you pressure test the radiator and see normal pressure I think that would eliminate heads as the issue...??

 

this only means at any giving time, you pass/fail. This will not eliminate the heads/block

The problem is; things can open up hot/cold. or Under Load/no load. Too many variables, this makes troubleshooting a bit more complicated.

 

JAKE SON is the 401 LT1 a misprint or did you stroke and bore it to 401...? AFAIK some folks have had trouble with big cube LTXs....(hitting coolant passages during clearancing ) So is it a 401 and was block fill used??

If your coolant leak is slow you could try some of these or bars leak gold.......


They just may solve your problem cheaply





Mike

 

Jake, the car didn't do this before your head-job.....now it does....

This could be as minor and improper torque sequence on the head bolts. Don't jump off the ledge just yet.....recheck your work, retorque your head bolts

 

Start from the begininning.
396 Engine with 3.875in crank, 6 in rods, and over bored to 4.060, making it a 401 LT1, block work done by shop. No block fill used.

Assembled engine myself: Terrible coolant leak, over heated quite a few times, upwards around 6-8. I made the mistake of using silicone on gaskets.

Replaced gaskets: Used Fel Pro Q9966PT ( http://www.summitracing.com/parts/FEL-9966PT/ )Coolant leak went to a trickle, put some steal seal in it and bar's leak head gasket repair. Still was at a trickle. Did not pay too much attention to it because i was blowing a lot of blue smoke out tail pip and had low compression numbers. Didnt know bout stroker ring on pistons .
Rebuilt Engine: So did rebuild, re-used copper head gaskets. Still had slow leak, put bar's leak seal in it no help. Drove car for 1 week, coolant leak got worse. No overheating

Replaced Gaskets: Pulled head gaskets and installed Fel Pro Q9966PT again, just finished on Sunday. Ran car, drove to work on monday, no change. Still slow coolant leak, no overheating. Put Bar's Leak in again, did not work. Left car in drive way and idle for a bit. Oil became contaminated and white smoke increased. Will not see smoke while driving, only at idle or in park, when car is not in motion.

Pulled Heads Just now: Here are pictures.


Spark Plugs: Installed on Sunday, less than 1x week ago. In order from left->right, 8,6,4,2


Number: 4, steamed white


Spark Plugs: Installed on Sunday. In order from left->right, 7,5,3,1


Plugs 3,5



Pistons 1,3


5,7


[Driver Side



2,4


6,8


Passenger Side




Driver Head

Passenger Head
[IMG][/IMG]

Passenger Head

 

So, am I interpreting correctly, it appears you've got symptoms of coolant getting to the multiple rear cylinders on both banks ?