Little bit of a backstory on this problem. 1995 Formula with just about 109K miles.
I was driving home about two weeks ago from a friends, everything fine and stopped at the store. Left a few mins later and not more than 5 mins after I was back on the road the engine overheated. Low coolant light was on and check gauges popped on, and I assumed a coolant issue. Had it towed back to my house and checked the coolant and noticed it had a good bit, but it was leaking somewhere since a good bit was gone since I filled it last time. After adding coolant and bleeding any air bubbles out of the coolant I noticed there was a small small amount of white smoke from the exhaust, but the engine ran fine and idled for 20+mins and a 10 minute drive without any temperature problems and the smoke was no longer there. So i assumed the white smoke was just from sitting and burning excess before it warmed up, but had me worried about the heads.

No long trips or problems for a few days, tried to drive it to a place around an hour away, everythings great and hit a set of train tracks that I had to wait at so I shut the engine and waited. Few mins after the trains passed started it again and drove no more than 1/4 mile and the engine was red hot(but no smoke, no sweet smell from the coolant). Pulled over and let it cool for a couple minutes, started it back up and it kept cool for the last 15mins and ran fine, now I think it could be the t-stat.

Two days after that I drive around 10miles away and it runs perfect as usual. Go shopping for an hour or two, start the car and hear a little clunk, sounded strange but couldn't find anything wrong so I left the parking lot. Again, no more than 1/4 mile after leaving I look in the mirror and see a decent amount of smoke billowing. Coolant levels were fine, check engine light was not on, nor was check gauges, and the temp level was fine but cut it anyways. Let it sit for around 5mins and started it, the smoke had cleared after a min and it was running clean. Exhaust did not feel real wet nor have any color in it, but decided it was 10mins home so I just drove it slowly monitoring the back, and no smoke.

Again fast forward two more days and I drove it around 2miles to the gym, no smoke on start up, but once I got there and it warmed up there was a pretty strong sweet smell with some smoke. Left the gym 1.5 hours later and no smoke on start-up, but once it warmed up and I got home, there was smoke and the smell again.

Sorry for the really long wall of text, but I hope it can help determine was issue. I find it surprising that the heads would leak so much, then just stop again. But I cannot guess anything else is the problem since smoke is the obviously result of a leaky or bad head. Any other guesses on my issue or anything I can check? Don't want to dive into my first head replacement if that's not the issue since it is my DD.

Things I have checked:
Coolant -
Oil Cap - didn't notice any coolant
Dip Stick

Thanks for any advice or answers, I'll be checking this thread a lot since I have a free Saturday and might start tearing down the top end today.

 

When my head gasket blew, the exhaust was mixing with coolant. Smoking very bad but no coolant mixing with oil.

Start it and remove the radiator cap see if its bubbling. I could also see the exhaust since it was cold out. Just my experience.


Posted from Camaroz28.com App for Android

 

Uh, no expert here, but I just found out my daughter's 94Z has a blown head gasket (possibly worse) and she was experiencing similar problems initially as you are. You may have caught it early before there is any severe damage. Hers ended up having fluid in the exhaust as well as in the oil. I'm hoping I didn't do any catastrophic damage by repeatedly trying to start it and bleeding off the pressure that would build up in the radiator and coolant lines. If I'd have put 2 and 2 together sooner I wouldn't have had to have it towed to find out about the blown head gasket. Now I'll have to have it towed back home so I can replace the head gasket(s) and verify that the head(s) isn't cracked.

I would have yours looked at soon. I think they can do a leak-down test to find out if and where the leak may be. Yours sounds minor and intermittent for now but it will get worse and then you'll be at the mercy of the shop that it's towed to.

Just my 2 cents.

Greg

 

Pull the spark plugs and you should find the bad cylinder real quick. When you overheated the motor you probably tweaked one of the heads ever so slightly. Not enough to break the gasket (yet) but enough that there is coolant seeping past the fire ring when it gets hot.

 

Do a block test on it, and see if the head gasket(s) are leaking. If it stops smoking warm, that usually means that the coolant is leaking in to a cylinder, and when it warms up, and things start to expand, the leak is small enough to partially seal up.

 

+1. If found, I would pull the head and check/replace gasket. Not hard to do at all.

 

Do a coolant system, through radiator cap, pressure test with radiator full. If it does not hold pressure and no coolant seen on the ground then check engine oil and check the spark plugs.

 

1995 z28 LT1.97,000 miles
Mine would run hot when idling. Finally, was losing a little coolant, then came a little steam and exhaust pipe was dripping. Happened to be home.
When I pulled the heads, the cylinder on the passenger side rear looked like it was steam cleaned.
I saw on this formum a long time ago, if you had an LT1, it was not a question of blowing a head gasket, just when. Kinda like the window motors going bad.
I'm almost have mine put back together.
I am going to lower the temp that the fans come on after I get it smogged. Mine were coming on about 228 . I think that is to hot when sitting in traffic. Maybe some one else can comment on that.
Once I had the exhaust manifolds off, I ground off the rivets of the heat shields. Now I can put the manifolds back on, change plugs etc, then put the heat shields back on when done, and safety wire them thru the rivet holes.
Makes it easy to get to the bolts on manifolds . I did replace the air pipe with hose for easy removal.
hope this helps

 

This.

Rent a Cooling system pressure tester from AutoZone. Apply around 10psi to they system and see if it holds steady at that presure. If not, you may be able to see or hear where the coolant is going as the pressure drops.

If you are having to constantly fill up the system, it has to be going somewhere. For sure, you need to find out where.

 

ill add my experience also. I believe mine started very similar to yours and then all of a sudden got very bad and milkshaked my freshly changed oil and started to hydrolock the motor. The point I am making is it does sound like a headgasket and if it is it is a small leak now and probably hasn't caused any damage. If it gets worse it can quickly cause major damage. Personally I would treat it as a blown head gasket and not drive it or start it except for any diagnostic purposes. my car had to sit two and a half years before I could afford to get her going again because a 150000 mile motor that milkshaked the oil and hydrolocked wasn't worth just replacing a head gasket so was time for a rebuild.


Posted from Camaroz28.com App for Android

 

If you're that far into it you may as well do both sides. If one of the heads has warped or gone soft then you'll want to have them both checked and surfaced equally. Also a good time for a valve job and maybe new springs.

 

Yes, I did both sides..Heck was that far, so did the valve job on both. Made sure the heads were not warped also...

I'm still learning. This is a lot different than my 1967 camero conv with the straight 250 6 in it...
frank

 

Well went from bad to worse, just like slick1hunting said. After I had the car towed back to my garage, I drove it around 2 miles into my town and had it looked at by a friend at his garage. Couldn't find evidence of leaky heads and we ran the motor for maybe 5 minutes. Fast forward to today, it hasn't been started since last week, try to start it and I hear a nice clunk. Pretty sure its a cracked head since the motor now seems vapor locked.

Worth it to tear it down or just go full on replacement?

 

Pull your plugs, sounds like water in the cylinder. Take off valve covers and pull the plug on the cylinder that has both valves closed

 

Yep,
Probably water in cylinder. Mine had water in 2 cylinders, as pizzi-man says "pull you plugs"
Water does not compress to well...
Hope it turns over with plugs out.
JR