Had the 93 out Friday for a drive. On the way back the low coolant light came on. Temps on the DIC never got about 190 and in fact held about 181/182.

However at one stop light it did belch hot coolant out of the auxiliary coolant tank so even though the temps at the temp sensor (DIC sensor in the radiator? or he head?) weren't high obviously got high enough for a hot bubble to escape.

Got home filled it with distilled water and went to start it up and it ran very roughly finally evening out nicely. I let it idle with a code reader on it from cold up to 188 deg F where I have Fan 1 turning on. No problems and no codes. Little bit of coolant was used from the aux tank. Topped that up and buttoned it up.

Tonite went out to do another coolant heating cycle and it wouldn't start. Strong battery but obviously no fire or no fuel at least at the right times.

No codes either.

I don't have my injector tester here but it is at my garage, but I can easily check spark tomorrow at the plug.

I can't imagine the heat (which I can't quantify as the temps never got high on the guage) cooked anything major as once I got it started it idled beautifully with no codes for the 8-10 minutes it took to get the coolant tips up to the mid 180's.

But the no start now does have me puzzled.

 

LT4Obsesses posted a good menu on another thread. I will stop by the garage tomorrow and get the fuel pressure guage, injector checker, and my spare pcm.

Quote from him:
There is the old fashioned way to check spark. start at the plugs with spark tester, test each one. If you're getting good spark at 3K+ rpm then it's not the ignition system.

If not, check for spark from the coil. If you're getting spark from the coil but not to the plug, then it's the distributor.

If no spark at the coil it could be a couple of things. Either the ICM is shot, of course the coil could be bad, or the opti harness is not secure or is bad, or of course the ecm itself is always a remote possibility.

Just for the fun of it, I would get a fuel pressure gauge and test pressure at the rail through the rpm range. Unquote

 

Blown head gasket? You might want to check for water fouled plugs.

 

I think not. Primarily because it ran so well after I let it cool and as I idled it up from full cold to 188 deg F or so after replacing coolant.

I will do the diagnostics but with the vented 93 opti I am concerned the steam generated from the burp may have gotten in the opti. And one of its failure characteristics is to run well after a wetting event and than corrode as it cools and die.

I have killed a number of optis with steam in my 93 Camaro. In fact I have several spares sitting in the garage but I think the optis are different as they are reversed in orientation. I may pull this one and rebuild it with internal parts from the F body opti's I have in stock.

With the F Body the opti replacement can be done in little over an hour. But we don't have interference with the front frame rail so can get the dampener off quite easily. Doesn't the motor have to be raised a bit in the Y body?

 

I've replaced the opti on a 95. We did not have to raise the engine. It did take a BFH, long piece of wood and some patience to beat the balancer off from the back side. It was not a fun project.

 

My first thought was head gasket as well. These systems are sealed and air tight, there should be no "air bubble" to push coolant out of the auxilary tank. Check you oil for signs of coolant, and check your coolant for signs of oil. Also, as mentioned, check the plugs to see if coolant fouled.

A head gasket leak isn't always a sudden event. They can be slow and progressive as well, then show early warnings, like this. What happens is the compression slowly expands the leak until it reaches the water jacket. Then it pushes the combustion gasses into the cooling system. It may start as very little air, but either the heat makes the surrounding coolant boil, or the air gets caught up somewhere an collects into a bubble that may get pushed through by the systems pressure, until it hits the overflow tank. But the car runs well, and at this early stage may not reflect a high temp yet, because it may be already passed the sensors when it happened.

The reason for the hard start and rough idle at first, is due to the engine cooling, and the coolant system still having pressure. It pushes coolant into that cylinder, thus fouling the plug. So on start up, it doesn't spark and that cylinder, or other affected cylinders will misfire on cold start. As the coolant works out of the cylinder, the plug will begin to fire and it will run better.

You may not have enough coolant in the oil just yet to create a change in overall appearance. But pulling the plugs is a good way to check for coolant in the cylinder. Also watch your temp gauge (digital) to see if the coolant temps rise faster than normal. On cold start, you can remove the cap from the surge tank, and as the coolant starts to flow, look for air bubbles, if you see those, it may very well be compression gasses in your coolant.

Due these simple checks first, you don't want to run with a bad gasket too much or you can warp the head. However, there can be other things. There could be air creeping in the system from a corrupted hose, the heater hose back flow preventer could be going bad, the temp sensor on the water pump could be going out, there could be a leak in the radiator, water pump going bad, or even simply the t-stat going bad.

But the air bubble in the overflow tank, and the followiing hard cold start would be a red flag for me. Check the plugs. Silly me, I almost forgot the sure fire test...a compression test will answer the question for certain.

 

My first removal of the balancer on my 93 Camaro was the same problem. At least on it I was able to buy and than use a huge open jaw pulley removal tool that gave me great leverage. The F body has huge space in front of the motor from underneath once the fans are removed from behind the radiator.

That lack of space is what I may be thinking about when I heard of the troubles doing the Opti on a Y body.

My first F Body opti change took about 4-6 hours. My last took little over an hour. After a while you get good at some of this stuff.

Actually the Y body looks easier excepting the crank pulley as there is more room to get at the front top of the motor once the air intake is off. But there is less room to get at the bottom.

The more I think of it, the more I am suspecting the Opti. It was a pita to start after it cooled down but once it did it ran like a dream while it was warming up and I was watching my autoxray all the way paying particular attention to sensor readings and codes for that 10-15 minutes.

A day later no start but strong crank. That delayed problem is so typical of steam or water generated opti failures.

The one thing I do worry about is that another sensor (cheaper and easier to access) may have gotten cooked by the steam from the burp and that it is not setting a code now because I can't get it to run long enough for the pcm to set a code.

The reason I have a couple of spare lightly used Optis in the garage is because I have twice replaced Optis on the Camaro thinking that was the problem and than to find out that it was another sensor at fault.

 

As far as your opti goes, before pulling everything apart, check the harness connector. I had a coolant hose blow. Got everything running, and did for awhile, but I happened to check harness connector some time later as I had a misfire once driving in the rain. When I pulled it, there had been a puddle of dried coolant in the bottom of the connector, that had started to erode the connection on the harness. Put a new harness on and quite frankly I realized that the car hadn't run this good since before the hose blew.

The optispark is more durable than many give it credit for. It was designed to live in a harsh environment.

 

Will do that now. My biggest problem is that I and the car are at home and my lift and tools are in my garage which is 18 miles away. So I am going to try the ez stuff first and your suggestion so far is the easiest. <g>

For those that suspect head gasket. Help me with where the temp sensor is that picks up the temp for the DIC? In the radiator? In the block? Or in the head? If a head gasket the hot water would be in the head. I was closely monitoring the DIC when the low coolant light came on and that never got over 190 deg F but that my not have reflected a hot spot forming by gases entering the cooling system.

My Helm manual is also at the garage.

 

The digital temp sensor, which is the one that supplies info to the ecm is located on the water pump.

 

So that could have been cool even with a bubble caused by combustion gases going into the coolant in the head couldn't it as it is reverse flow.

My experience with a "pushed" head gasket was 50 years ago on a 2 year old AH 3000 and in that case it would overheat but once cooled down would start again without problem but would overheat very quickly.

This is simply not starting. The female portion of the opti harness (as well as the male portion were bone dry when I disconnected it. The wires down there were somewhat wet however even though all the coolant lines seem intact without tears or leaks.

All this has me continuing to think of a steam incursion into the vent on the bottom of the 92/93 opti, which is why they took that vent and closed it up with a small tube in 94 and later.

I am pretty sure I can remember the tools I need to pull the front of the car off to get at the water pump and opti and have learned to replace both while you are there. The car only has 39,000 miles on it but it is the original opti and original water pump.

So lots of 13 and 15 mm with an occasional 10 mm and that bfh and wood to get the dampener off. I do have a number of very large pry bars that also might work. I also have a gear puller that I might be able to get in there.

Prior to pulling it apart I will check a number of the plugs but I am not to certain of a head gasket causing a no start condition but it is easy enough to check by looking at the oil on the dipstick.

 

Very cool!! Although the accessory drives are reversed 93 Y to F body the Opti is not. So I have two slightly used Optis from my Camaro in the garage that will fit.

Next decision is whether to replace a working water pump when I pull this one. And at $300 for the part, I may not.

 

Well I couldn't find either of my old slightly used Optis so ordered one from Sac City Corvette. It arrived and all I needed to get in the car and replace it was the gaskets for the water pump.

However there is an advantage of not using an older car as a DD.

I went out last night just to see if it would start and it did. So apparently I was correct and the overheating had gotten steam in the Opti. But a couple of weeks of sitting allowed it to dry out.

No codes and smooth idle with all sensors reading well within their normal ranges. I will actually take it out for a drive today. Gotta love good Chebbys.



Perry

 

Found the problem. And how simple. Remember the TB Coolant Bypass mod? Simply plug the tee from the upper radiator hose to the TB and plug the return line. After 15 years that female rubber cap I put on to cover the tee finally developed a pinhole leak. As the coolant heated up and the pressure in the radiator increased that pinhole leak would open and hot coolant would spray on the front of the motor. And that is not a good thing for an opti.