98 Z/28 got a problem- help please

**LETHALxLS1** · 09-22-2010, 07:28 PM

A few weeks ago I notice the low coolant light on my dash lit up. So I fill the overflow res next to the radiator up with dexcool 50/50 mix with H20. I hardly ever drive the car and it stays stored in the garage. The other day I drove the car and noticed the low coolant light on again (it was off for the first 15 minutes I drove it).

I run the ac every time I drive and the temp only gets to 180 max (I guess cause the fan is always on if running the ac).

I decided to check the level in the radiator and it was full. Before putting the cap back on I started the car to purge the air from the system. I let it run for 15-20 minutes with the ac off and after it bubbled the level went down a little- I added more dexcool and put the cap on. The temp was 210 on the gauge. I noticed a weird sound when I shut the car off like a shpshhhhhhhhhhhhhhh sound. I never heard this before ever.

So I decide to try to purge the system again. I let it run 10 minutes with the cap off and all of a sudden coolant starts spewing out of the fill hole on the radiator and its boiling/steaming.

I never heard the fan cut on the whole time it was running but when I turn the ac on I hear the fan for that. Can you hear the fan that comes on first or is it a low velocity fan? I can'y get down there to look due to recent health issues.

Why would the coolant do that? Could my thermostat be stuck? or could it be a fan problem? Temp sensor problem? The coolant seemed much hotter than 210 degrees.

Any ideas? Thanks in advance.

**My00Z28** · 09-22-2010, 09:45 PM

any car when the coolant gets too hot it will start to over flow thats what happens when your cap is on and it goes in the overflow tank. my car ALWAYS runs at 210 no matter what i do it never moves. iv noticed my car make the "shpshhhhhhhhh" noise also but never think of it being a problem. your coolant level sensor could be going bad...

**LETHALxLS1** · 09-22-2010, 11:00 PM

Originally Posted by My00Z28

any car when the coolant gets too hot it will start to over flow thats what happens when your cap is on and it goes in the overflow tank. my car ALWAYS runs at 210 no matter what i do it never moves. iv noticed my car make the "shpshhhhhhhhh" noise also but never think of it being a problem. your coolant level sensor could be going bad...

Maybe I just never heard that noise because (according to the temp guage) the car never runs hotter than 180 degrees?

I think the level sensor is bad- like you say. Do you know if the temperature sensor (located in the drivers side head) would cause the check engine light to go on if it was bad?

I am wondering if my temp guage is reading low because of a bad temp sensor.......

Thanks for your reply I appreciate it.

**My00Z28** · 09-22-2010, 11:14 PM

The check engine light can come on from a bad thermostatt the code would be like "coolant temp under thermostat threshold" or "over" if its a stat but our ls1's take a 186* stat OEM... and yes bad temp sensor will also cause ses lights...

**F55c6** · 09-23-2010, 10:33 AM

I have a 98 and the coolant level sensor went bad. Its a very easy fix. Remove the battery and look on the passenger side tank of the radiator about 3 inches below the filler neck. You will see the sensor with a wire that goes to your light on the dash. The sensor has a spring loaded wire clip that holds it in the tank. Drain the radiator a few inches below this point and use a small screw driver to pop the clip over the lip, which will allow you to pull the sensor straight out. I tried cleaning it and it was a waste of time. Just buy a new sensor and be done with it. Pop the sensor in, refill the radiator, put the battery back in and no more light. I would not allow the car to heat up while filling the radiator. It is going to boil over at a lower temperature since it is not under pressure. Turn on your heater and run the engine while filling, but do not let the temp go to 180. put the cap on and fill the overfill tank. Let it cool then recheck.

**LETHALxLS1** · 09-23-2010, 11:57 AM

Thank you guys for the replys. I really appreciate it.

So a bad/stuck thermostat would cause the check engine/ses light to come on? That is pretty amazing but I don't understand how it can do this.

I am going to get a laser thermometer for $30 bucks just to be certain my temp guage inside the car is accurate just to be sure.

**My00Z28** · 09-23-2010, 06:32 PM

If your thermastat is stuck open that would cause your coolant temp to be lower than its suppose to be causing the an ses light if it wwere stuck closed your car would over heat....

**LETHALxLS1** · 09-23-2010, 06:41 PM

Originally Posted by My00Z28

If your thermastat is stuck open that would cause your coolant temp to be lower than its suppose to be causing the an ses light if it wwere stuck closed your car would over heat....

Ok I was thinking he meant it would throw a code if the thermo was stuck closed- which made me be like

Thanks man

**LETHALxLS1** · 09-29-2010, 10:42 PM

OK.... I am certain the low level coolant sensor is bad (like someone mentioned earlier) and like I was suspecting.

I purged the air from the system, put the cap on and let it run for 15 minutes.

I bought one of those thermal laser temperature guns and checked the accuracy of my Z's temperature gauge. The gauge tested accurate. The gun read about 5 degrees cooler than my car's guage which seems about right.

According to my owners manual- you don't have to wait for the thermostat to open to purge the air from the system.

Anyways- thanks for the help. I feel like this now-