If anybody has any good advice on bleeding air pockets out of the coolant system in an LTx engine / LTx radiator, please fill me in. Any help is appreciated.

The water pump works, but the temp goes up and the radiator is cold

 

I added the water with the motor cold. Filled it up, heard it gurgle gurgle gurgle, watch the water go down. Filled some more rinse/repeat until you get no more gurgles. Then started the engine up with the cap off, waited until the water got pushed up to the top of the radiator, put the cap on, opened the bleeder valve on the thermostat neck (after putting some towels down so it wouldn't drip on the opti) and waited until I got a good stream coming out of it. Then shut it down, popped the cap filled it some more. It takes a while to get it all out, I would say it took me close to 30-45 min to get it all out. Mine runs at 190 driving with no problems.

Now if yours is heating up while driving, do you still have the front air dam on the car? I took mine out for a test drive before I put it back on, and she overheated on me, never touched the coolant but put the air dam on and no problems.

Also do you have all the lines hooked up or a couple capped?

 

The air dam is still there and it overheats regardless of if it is sitting still or moving. All of the lines are hooked up as well. It seems I have tried what you said, but with no luck.

What is odd is that I am not really getting much hot water into the radiator as the radiator is cold to the touch.

I am begining to blame the water pump, even though it seems to be partially working. I can see water returning to the radiator from the head return line by looking through the radiator cap opening. Also, the head return line is hot as are the heater lines. The main hoses dont get overly hot.

When I hold the heater hoses, the water going through them feels cavitated.

I have everything plumbed the same as last year, just that the pump sat over winter in a parts bin. Last year the temp never got over 180, even with continuous runs at the strip. I now also have a new thermostat and radiator cap. The radiator is only a year old.

Is it possible for a water pump to work partially but not very well (i.e. the impeller slipping on the drive)?

 

have you tried removing the thermostat and running it like that?....also, how is your heater core, i've seen a lot of cars overheat because of that

 

What happens on mine is the temp gauge goes all the way up to 260, then the thermostat opens eventually and the temp goes down to like 160. Sometimes the heat coming from the vent is cold until that first time the thermostat opens, which is normal, then it gets hot like it should. This continually happens unless I'm driving on the highway, then once it gets to 160 it stays. Do I need to bleed the system more?

 

do not remove the thermostat, it will only make cooling matters work. I proved that time and again to myself when I was searching out my cooling problems. Mine ended up being the radiator. I had used some stop leak before when I had a pinhole in it. Come to find out it had clogged up the lower half of the radiator. Had it rodded out, NEVER gets above 180ish now.

 

Because of the reverse flow cooling, LTx cooling systems need to be bled. On the Tstat housing, there should be a bleeder. Jack the front of the car up as high as you can(helps get air out of the back of the heads). Start it up, open the bleeder. Leave it open till your getting a steady stream of water and no more air out of it. Be sure to have a rag under it so you don't get to much water on the Opti.

 

I've never jacked it up. just start it up, let it get up to temp, open it up and let it sputter. close it and let it heat back up again. repeat until steady stream.

 

I noticed today that my headers are too close to one of the heater core inlet/outlets where you hook up hose to go to the waterpump. As a result the hose melts and coolant leaks out. My temporary solution is to not use the heater, but how can I fix it? Sometimes it gets cold in the cab and I would like heat, and it also helps bleed off a lot of heat if the car gets too hot.

 

I assume you're using LT1 heater hoses. Just buy a few feet of heater hose from a parts store and route it over the top of the engine going inbetween the valve cover and the intake manifold. Or figure a way to route it differently.

 

I'm using just regular heater hose. I'll take a picture today, when I posted last night it was dark.

 

Here is what I thought was happening. I thought that the header was melting the heater hose. What was really happening was that the hose clamp holding it to the heater core wasn't on tight enough so there was air getting into the system. Well on the way home I had overheating problems, and then I come to find that the coolant temp sensor for the gauge melted, and the block heater shot out of it's hole, leaking all the coolant on the ground. There musta been hella air pressure or something to make that happen, hopefully I didn't crack the heads or block.

 

Thanks for the help guys. Right now it is cooling fine without the thermostat. It still gets up to temp properly,etc. The radiator is only a year old. I am guessing that the radiator is too small for the new engine. I will leave the t-stat out until funds allow for a bigger radiator.

I also popped my heater core while working on this. It was probably bad for a while and not helping matters either.

 

I fear I have either blown a head gasket or cracked a head. How can you tell which happened? My car overheats when driving in cold weather even with the fan on. I know the thermostat is working because the return line to the radiator is hot. I get no hot air at all from the heater core. My exhaust smoke seems to be more white than it should be, and seems that there is more condensation than normal dripping from the tips. I tasted the condensation and it seems that it is a little sweet. How can I tell what happened, and how hard is it to change head gaskets, like how long would it take?

 

I am starting to think the same thing as far as the head gasket for my situation. I dont think it is the head (or at least hope it isnt) as they are fairly new.

The reasons I think mine has something related to that is as follows:
1) LARGE amount of condensation in exhaust on startup
2)coolant disappearing (and not into the oil)
3)HIGH amount of pressure on hoses when running
4)cooling system failed a vacuum test
5)I had 1 loud knock on startup the other day (thinking it was a possible slight hydraulic lock on the bad cylinder)

The car is going to have to sit until I pull the heads. I will probably let it sit for a few days and pull the plugs and crank it. I see if I blow any coolant out of the plug hole of the bad cylinder.

I just hope I didnt wreck anything when I had that possible lock. I couldnt figure out what that was at first as it was only one loud knock and not repetitive. This would explain it.

 

We are having similar issues. I pulled my heads today and definately noticed that I had a blown head gasket on the driver's side. The passenger side seemed ok. I am going to have the heads checked this week for cracks or warping. Let me know what you find out.

 

Will do.

What heads and head gaskets are you running?

 

When I put my motor back together, I went with the stock Fel-Pro PT gaskets.

You guys did change the headbolts as well, at some point in '95 they went to the torque to yield bolts that have to be swapped when the heads are pulled.

 

Thanks for the info on replacing the head bolts, I'll be sure to do that. These are the original head gaskets and the heads are stock. I am almost certain this is the first time this engine has been taken apart.

 

Quick update. My heads are warped. I am having them resurface the heads for me, it only costs $25 a head. I was going to have them ported and polished too, but nobody in town will do it for me.

 

The current gaskets are Fel-Pro 1074's. I replaced the stock bolts with Manley bolts.

I hopefully will have time to pull the heads tomorrow before work.

If I can narrow the problem to one specific cylinder, I was planning on leaving the other head alone and bolted on. Is that a bad Idea?

 

I'm running the 9966PT gaskets, no problems at all so far. Also used the Fel-pro head bolts.

 

I knew it wasnt good when I pulled my number 6 spark plug and coolant ran from the hole.

I pulled the heads (both) and number 6 was near the bottom of the stroke and was full of coolant.

Nothing stood out as an obvious problem. Heads look OK, but are getting checked out at a local engine shop. There appears to be a ridge around the bottom side of the gasket (block side) around the cylinder on number 6 only.

At first, I thought Fel-Pro messed up the gasket, but the closer I look, it looks like the the cylinder may have a liner in it and it may be getting pushed down when the head is put on.

I am going to talk to the guy that built the engine tomorrow and see what he says. Ill keep you guys posted.

 

The cylinder is sleeved and there is a small crack between a head bolt hole and the sleeve. The guy who built it is going to build a new one for me out of his pocket.

On the bright side, I definitely found my cooling issue

 

I put my car back together this weekend and it is working fine now. The only problem now is that I have the fan wired to a switch that is on the same circuit as the foglights that I also installed and I keep blowing the fuse. For now I will fix it by not running both at the same time and I should be fine. You sure got lucky that he is going to fix the problem for you. After I fixed mine I had spent about $200 in parts and prolly about 12 hours in work. I got a couple other things done, I removed all the a/c stuff and also got the emissions garbage cut off my headers so it is easy to get at and also easier to work on.