Help! 1994 LT1 Service engine soon light turns on and off

[SnakeDr]

New to this area is O'Reilly's parts who will sell/take return on a testing kit; so, it's free as long you return it within 48 ( I think) hours. Their kit includes a cap tester.

Emphasis MINE, in case you need it; an amazingly SHORT time for corrosion to start, especially on those aluminum parts... like heads. OI didn;t think it'd be alone in there for long, then life happened.

Don't repeat my mistakes, please.

Yep. Flushed it again this morning to prepare it for coolant. Got everything out and removed/cleaned the overflow bottle pretty good. Also used my wet vac to blow all the water out. I filled and flushed the system several times until water was clear.

I bought a bottle of water wetter and filled her up with Dex-cool. She appears to run a bit cooler than before.

It was 90 degrees today. In stop and go traffic, with the A/C on using the digital gauge it peaked at 230 degrees in stop and go traffic. Then took her on a back road cruise turning the a/c on and off temp was in the 217-225 range. This was about a 1.5 hours of driving.

My last test was to let it sit in the driveway and idle for about 10-15 minutes. Temp held at 230 degrees.

So far so good.

 

[WhalePirot]

I love happy endings.

 

[John Robinson]

That looks normal. I was driving the wifes' 2006 Pontiac the other day in 100 degree weather. The temp on it was at 220 degrees and that reminded me that it runs that temp all the time summer or winter. Apparently GM has engineeried the cars to now run at these temps. Our problem is that for a number of years the manufactures did not provide any type of gauge just an idiot light. With the Corvette being a sports car it was expected to have a full set of gauges so we could monitor what it was doing. I to was concerned about the temp I saw until I read somewere that GM expected the Corvette to run as high as 240 degrees without being in trouble. Having a gauge saved me from a problem when I developed a leak in a radiator hose on the highway and I noticed the temp going up because I was losing fluid. That allowed me to find a service station and to fix the car before it stranded me out in the boonies somewere. For that reason I vote for having a full set of gauges. Thanks for letting us know what fixed your problem I am sure it will help others as well.

 

[SnakeDr]

That looks normal. I was driving the wifes' 2006 Pontiac the other day in 100 degree weather. The temp on it was at 220 degrees and that reminded me that it runs that temp all the time summer or winter. Apparently GM has engineeried the cars to now run at these temps. Our problem is that for a number of years the manufactures did not provide any type of gauge just an idiot light. With the Corvette being a sports car it was expected to have a full set of gauges so we could monitor what it was doing. I to was concerned about the temp I saw until I read somewere that GM expected the Corvette to run as high as 240 degrees without being in trouble. Having a gauge saved me from a problem when I developed a leak in a radiator hose on the highway and I noticed the temp going up because I was losing fluid. That allowed me to find a service station and to fix the car before it stranded me out in the boonies somewere. For that reason I vote for having a full set of gauges. Thanks for letting us know what fixed your problem I am sure it will help others as well.

Special thanks to Hib and John and everyone else who pitched in.

I smoked my 1969 442 motor over a idiot light in the early 1990's. It had over 100k miles but a pinhole leak and a undersized replacement radiator were the root cause. Ended up rebuilding the engine and transmission. Also this car LOOKS really nice, I hear it all the time but was behind in maintenace and neglected.

Just wanted to make sure before I moved on to other pricey projects on this car that the engine was okay. The car was sitting for 3 years and i must have stirred up the pudding (sludge) when putting it back on the road. I should have changed it on general principle.

Thanks again.

 

[93Rubie]

Yep. Flushed it again this morning to prepare it for coolant. Got everything out and removed/cleaned the overflow bottle pretty good. Also used my wet vac to blow all the water out. I filled and flushed the system several times until water was clear.

I bought a bottle of water wetter and filled her up with Dex-cool. She appears to run a bit cooler than before.

It was 90 degrees today. In stop and go traffic, with the A/C on using the digital gauge it peaked at 230 degrees in stop and go traffic. Then took her on a back road cruise turning the a/c on and off temp was in the 217-225 range. This was about a 1.5 hours of driving.

My last test was to let it sit in the driveway and idle for about 10-15 minutes. Temp held at 230 degrees.

So far so good.

Not to alarm you but I still think 217-225 on the digital read out is too high for open road driving. In the city yeah, it will get up to around 230 then go down once the fans kick on that is normal.

My 93 runs right around 190-194 on the open road (above 45MPH, few stops, A/C on) on even 80+ degree weather with high humidity. I've never had it out when its like 95+, low 90's=same. Runs this temp. all the time regardless if A/C is on or not. Granted my cooling system is in top notch shape, new hoses, t-stat, cap, coolant, etc....you could just about eat off my radiator and condenser, it is clean. Lots of heat transfer to the air, because the air can flow across my rad/condenser. Make sure you don't have a bunch of junk clogging up your rad/condenser.

 

[John Robinson]

Not to alarm you but I still think 217-225 on the digital read out is too high for open road driving. In the city yeah, it will get up to around 230 then go down once the fans kick on that is normal.

My 93 runs right around 190-194 on the open road (above 45MPH, few stops, A/C on) on even 80+ degree weather with high humidity. I've never had it out when its like 95+, low 90's=same. Runs this temp. all the time regardless if A/C is on or not. Granted my cooling system is in top notch shape, new hoses, t-stat, cap, coolant, etc....you could just about eat off my radiator and condenser, it is clean. Lots of heat transfer to the air, because the air can flow across my rad/condenser. Make sure you don't have a bunch of junk clogging up your rad/condenser.

I don't disagree with you on these temps but since he had done a flush and had not run a number of hot cold cycles to purge the air it probably is acceptable. I think after he has driven and let it cool 4 or 5 times(with the overflow tank nearly full of water) the temp will settle down into the range yours runs in. This last summer when I blew a radiator hose on the road and did a road side fix and filled mine with water it ran in the range he is seeing now. When I put in a 50/50 mix and drove it for a week I noticed that mine was running 193 to 197 in town also.

 

[SnakeDr]

Not to alarm you but I still think 217-225 on the digital read out is too high for open road driving. In the city yeah, it will get up to around 230 then go down once the fans kick on that is normal.

My 93 runs right around 190-194 on the open road (above 45MPH, few stops, A/C on) on even 80+ degree weather with high humidity. I've never had it out when its like 95+, low 90's=same. Runs this temp. all the time regardless if A/C is on or not. Granted my cooling system is in top notch shape, new hoses, t-stat, cap, coolant, etc....you could just about eat off my radiator and condenser, it is clean. Lots of heat transfer to the air, because the air can flow across my rad/condenser. Make sure you don't have a bunch of junk clogging up your rad/condenser.

:ugh Darn...

 

[SnakeDr]

I don't disagree with you on these temps but since he had done a flush and had not run a number of hot cold cycles to purge the air it probably is acceptable. I think after he has driven and let it cool 4 or 5 times(with the overflow tank nearly full of water) the temp will settle down into the range yours runs in. This last summer when I blew a radiator hose on the road and did a road side fix and filled mine with water it ran in the range he is seeing now. When I put in a 50/50 mix and drove it for a week I noticed that mine was running 193 to 197 in town also.

Let see what happens over the next week. System should be purged by then.

 

[SnakeDr]

Let see what happens over the next week. System should be purged by then.

Where is the dirt usually caked in at? Is it the rear or front of the radiator?

I think my next step is remove the radiator. It's very hard to see if its clogged with dirt. Whatever condition its in I will take some pictures.

How do you know the water pump is bad on this car? A pressure test? This is more of a closed in water pump.

This car spent most of its life in the South East. It's last home was in Florida before coming to NJ.

 

[93Rubie]

Yeah, I did not know you had not had the 3 hot/cold cycles yet. Keep an eye on it and see what happens.

You don't need to pull the rad to clean it out. Just pull the shroud. Any junk on/between the rad/cond. will be obvious.

 

[John Robinson]

Earlier I pointed out that I was able to clean the radiator by putting a crevice tool on my shop vac. All you have to do is lay under the front of the car (you dont even have to jack it up) and you can get between the AC condensor and the front of the radiator. Vacuum the front of the radiator and then reverse the vacuum hose so it is bowing and blow the back side of the condensor. This is easier than removing it. If you really want to know if the radiator is ok or has a blocked section of coils get a infrared temperature checker. With the car to temp go under the front and spot check the radiator to see if the temp is even all over it. That will tell you if you have a blockage or plugged section in the coils of the radiator. You can also use the temperature tester to see what the engine and head temp is.

 

[SnakeDr]

Yeah, I did not know you had not had the 3 hot/cold cycles yet. Keep an eye on it and see what happens.

You don't need to pull the rad to clean it out. Just pull the shroud. Any junk on/between the rad/cond. will be obvious.

Thanks for the good news Rubie. I was dreading pulling out the radiator.

I may pull the shroud off tomorrow night. Today is a holiday...got to spend time with the Mrs...

 

[SnakeDr]

Earlier I pointed out that I was able to clean the radiator by putting a crevice tool on my shop vac. All you have to do is lay under the front of the car (you dont even have to jack it up) and you can get between the AC condensor and the front of the radiator. Vacuum the front of the radiator and then reverse the vacuum hose so it is bowing and blow the back side of the condensor. This is easier than removing it. If you really want to know if the radiator is ok or has a blocked section of coils get a infrared temperature checker. With the car to temp go under the front and spot check the radiator to see if the temp is even all over it. That will tell you if you have a blockage or plugged section in the coils of the radiator. You can also use the temperature tester to see what the engine and head temp is.

Real good information. Like I said before dreaded removing the radiator. Dealing with the coolant is so messy.

 

[SnakeDr]

The Mrs got misty eyed, when I told her helpful you guys have been...

 

[SnakeDr]

What I found

Earlier I pointed out that I was able to clean the radiator by putting a crevice tool on my shop vac. All you have to do is lay under the front of the car (you dont even have to jack it up) and you can get between the AC condensor and the front of the radiator. Vacuum the front of the radiator and then reverse the vacuum hose so it is bowing and blow the back side of the condensor. This is easier than removing it. If you really want to know if the radiator is ok or has a blocked section of coils get a infrared temperature checker. With the car to temp go under the front and spot check the radiator to see if the temp is even all over it. That will tell you if you have a blockage or plugged section in the coils of the radiator. You can also use the temperature tester to see what the engine and head temp is.

This is what I found. Some previous posts around the web, showed dirty radiators/condensors with heavier debri, for example like the car sucked up a bale of hay or leaves. What I found was a bit deceiving.

Looking at it from the passenger side slot was deceiving. However what I actually found was the radiator appears to be clogged with sand. Now since, this car was actually in the south, lastly in Florida this makes sense. I didn't put it back to together tonight. I did a combination of blowing out the dirt/sand with compressed air and blowing out the air with the shop vacuum. If anyone has anymore tricks let me know. I will blow it out one more time tomorrow night before putting it back together.

Do you guys think there was enough dirt to cause it to run hot?

 

[93Rubie]

The close ups of the fins tells the story. The way they are packed full of sand, that would definitely cause it to run warm. No heat transfer, very poor at the very least.

 

[SnakeDr]

The close ups of the fins tells the story. The way they are packed full of sand, that would definitely cause it to run warm. No heat transfer, very poor at the very least.

Getting the sand out was not easy. I couldn't get it all out 100%. I made several passes with a combination of of compressed air and reverse flow of the shop vac. Then repeated the same process above several times again.

I just put it back together and fired her up. Took her for a spin but of course it's now cooler about 69 degrees. Using the digital gauge and cruising from 45 mph to 60 mph my temperature readings where about 186 to 195 degrees. For long stretches of cruising it was in the 185 to 188 degrees range.

Despite the weather, turned on the A/C and was in the 185-188 degrees.

I will keep an eye on it and update in a couple of days.

 

[John Robinson]

How difficult was it to remove the shroud?

 

[SnakeDr]

How difficult was it to remove the shroud?

Not hard but time consuming. I have air tools so it was easy to take apart except for one area. There are three small screws on bottom front left and right in the very front of the car. You have to take out the overflow tank and A.I.R. Pump to get to them from the side. Wasted a lot of time trying to get those 6 screws out and back in. I have big hands so I had to sit on the tire or straddle it and turn my hand a certain way to start the top screw when putting them back in.
The bottom two screws I used a 7 mm socket with some masking tape to hold the screw in with a extension to start them.
You can also lay on the ground in front of the intake and realign the clips if need be.
One more thing, its probably better to drop the coolant and remove the radiator. You can clean the radiator fins thoroughly and have better clearance on both sides for the condensor.
I will probably clean it thoroughly sometime down the line in spring 2013. For now lets see if this is good enough. Sure its the cleanest its been in years. We will see over the next couple of days.

 

[John Robinson]

Thanks for the information. I have started to remove mine a couple of times and quit because it looked like I was getting most of the front of the car disassembled