KnowYurEnemy54

Hello everyone,
I’ve had my z28 for about a year and a half and I’ve been trying to chase down an over heating/coolant overflow issue for pretty much the whole time. Most recently replaced the thermostat,temp sensor, and heater core. The heat is now working perfectly,where it wasn’t working at all before, and the car is running strong. The problem is still with the rapid overheating and overflow of coolant from the overflow reservoir. Most recently, I was driving it the day before Christmas and took it for a five minute drive, parked it for about 15 minutes and got back in and the temperature was fine. Started up and drove fine and then on the way home I hit the gas really hard a few times to get on it for a few seconds. I noticed the cars tires weren’t gripping right, remembered this happening from previous times, looked at the temp sensor and it was immediately all the way at the top. Luckily, I was a block from home and parked the car on my driveway, which is on about a 22 degree incline(I don’t know if that matters at all) and just like before, the overflow is pouring so much coolant. I was pretty disheartened and feeling like nothing is going to fix this issue.

I’ve been visiting this site for over a year and reading all the advice, but I thought it was time to come right to the source with my issues.

the car also has the Ligenfelter upgrades. Not sure if it’s stock that way or was added after the fact. I am the 3rd owner. 67k miles.

thanks in advance and happy new year!

shoebox

Anytime I hear of coolant flowing out of the remote reservoir, it is usually because the overflow and steam pipe hoses are switched at the radiator. The other possibility is a bad radiator cap.

KnowYurEnemy54

I’ve kept seeing this as a possible cause in other similar threads. I will investigate further into this. Is there any other diagram I should need or will this one picture suffice?

thank you!

Injuneer

This is another Shoebox aid…. clarifies the routing of the radiator hoses.

Radiator overflow hose from top connection on fill neck is #27, steam pipe flow is routed through throttle body, then hose #5 to the lower connection at the fill neck. If someone has bypassed the coolant from the throttle body the steam pipe may be routed directly to the radiator.

http://shbox.com/1/95-97_hoses.jpg

Rapid heating could be a blown head gasket, over pressures the coolant system, the 18 PSI cap opens to relieve the pressure, and coolant dumps into the reservoir.

KnowYurEnemy54

we have had multiple head gasket test done to eliminate that as a possibility. I’m not getting any of the other telltale signs of a blown head gasket either. I’m not saying it isn’t that, but I’m hoping it isn’t. Early on, we replaced the radiator cap, had it overflow again, and then went back to the original cap. It seemed to help for a while. I did read on another thread about someone buying a Scant radiator cap that was like 3mm deeper than the original cap and that helped him. I don’t know what a Scant cap is though and I’m wondering if it was a typo. I have found a Stant radiator cap online.

I also saw on another post that there is something that is supposed to remove the coolant from the overflow system but I can’t remember where I read it or what it was. Apparently it deteriorated in this other persons issue.

Injuneer

“Stant” is a radiator cap brand.

The radiator developes a vacuum as the coolant cools down. That pulls the coolant out of the reservoir into the radiator and keeps the radiator full. If there is a leak in the coolant overflow line, the vacuum is lost and the radiator doesn’t refill.

KnowYurEnemy54

could the radiator itself be clogged or need to be replaced?

Injuneer

A plugged radiator could cause the overheating. So could something as simple as debris blocking the front of the radiator. A simple plastic bag can cause major issues. A missing air dam under the front bumper can cause overheating at freeway speeds.

Are you sure you installed the correct LT1-specific thermostat (what temperature)? Which coolant temp sensor did you replace? Are you sure the fans are working? Have you scanned the PCM for codes?

Both fans should come on at low speed at 226°F, and switch to high speed at 235°F. The PCM reads the temperature from the sensor in the water pump housing. The gauge has its own sensor. The two sensors sometimes don’t agree.

Injuneer

No, because you are a SPAMMER from Bharti Airtel in INDIA with a fake name.

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ACE1252

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