FL87Z52

So, I've replaced everything and now when I start it up the temp gauge climbs rapidly all the way to 260 so I shut it off and check everything. Everything is fine. The thermostat is opening. The car isn't hot to touch when the gauge says 260. The coolant is full. The thermostat is opening like I said because I can feel stat open a make the radiator hose hot. The sensor did climb to 230 then drop to 193 then back up to 215 and bounced up and down a little. Could I have an air bubble or something. How would I get rid of this or is the sensor in the cyclinder head bad now. 87 L98 Z52

lefoy84

Year of your car? L98s and Lt1s are different.

FL87Z52

sorry 87 L98 Z52

AGENT 86

Open the rad cap and start the motor. When the stat is surely open, have someone keep the rpm steady at about 2000 rpm while you fill the rad. Once full, cap it and return to idle. That should take care of any air.

FL87Z52

Would that solve the gauge problem also?

AGENT 86

Good chance if you have air trapped in there.

Aggravated4life

Ive seen this happen many times with the L98 engine...I have a TIP for people doing coolant part changes,such as water pump,always,and I mean always,top your engine off with coolant before the radiator top off.

I would pour coolant into the intake hole where the T stat goes and keep filling slowly until it wont take anymore,then put the T stat back on,etc.This will greatly help the air problem and I also pump the coolant hoses by hand to increase the air burping before putting the cap on the radiator and starting it up.

Takes longer but ensures it wont overheat and act up.I sometimes turn the pump pulley by hand a few times after topping rad off and watch the bubbles push out of the radiator filler cap area.Then I cap it off when it seems FULL and cant get anymore air bubbles out.

Of course the tip posted earlier to rev the engine and top off to purge it of air works great too.

The reason you see 260+ degrees is the engine isnt full of coolant,but your radiator is,and it will show it get real hot and the T stat isnt gonna open yet,even tho dash says otherwise with temps.I believe the dash reading is from the sensor in the Head.

With continuous air pockets,youre gonna get hot spots in the block or heads and show the dash reading to go way up,even though the coolant in the rad is nowhere near as hot.

runner140*

I don't think you have a gauge problem, you have an air in the system and need to burp it.
Use both hands on this---With radiator cap off, bring up to temperture, and when you see the coolant flowing, with your right hand, rev engine to about 2000 rpm's and with your left, fill coolant until it is full. While still at 2000 rpm's --left hand, put the radiator cap back on.

You may still need to open the bleed screw to get all the air out of the system.

I'm not sure even I understand the above. Good luck.

FL87Z52

Thanks everyone for the help. I did let the car heat up enough for the thermostat to open then reved it to 2000 it then took almost a full thing of coolant fill it back up. Thanks again.

CALI C4er

I changed my radiator last weekend. Put in a DeWitt's. I have a new 160 thermostat and a new water pump. When I started it up it shot up to 250. I shut it down and checked for leaks. I couldn't find any. I checked the fluid level and it was full. It started it and again it ran awhile till it got real hot this time I had the cap off. I tried to add more coolant but it was full. When It cooled down I decided to take it for a quick ride. I figured it was running hot because it was idling inside my garage. The temp dropped like a rock. It went from 250 to 190. I drove it back and it took about another gal. I went for another long ride this time and the temp never got over 190. I have a 88 z52 so you problem is similar to mine.