Thread: Temp rising and falling after w/pump install

Hey Guys,

Need help...Temp gauge rises and subsequently falls as I am driving. This is after I installed a new water pump. New coolant was added after a complete flush. In fact, this is the second flush. The first one was just last week when the LIM and v/c gaskets were replaced. Apparently the water pump decided to quit after the LIM job.

I checked the coolant level and it seems fine. Not sure if bleeding air would help. Do I need to replace thermostat, radiator, temp sensor etc...

I just replaced the rad cap...So let's see if this fixes the problem.

id think u prob have air in the system still... did u bleed it out at all?

Originally Posted by gtpinsc

id think u prob have air in the system still... did u bleed it out at all?

Yes...Used the bleeder screw along with some suction..My GM mechanic performed the work and pretty much said the same thing about air in the system...I know I had to add a little coolant (1-1.5 cups)...Not sure how else to bleed the system.

the bleeder screw is the only way i kno how too... maybe crack that thing open and bleed it for 10 mins or so til all the air bubbles stop and its just coolant leaking out.

Do I do this with the motor running?....I did not personally do this before...The mechanic told me about it and indicated that he did it.

yes car must be running. it must get to proper operating temp, so about 10 min at idle should do it, open the screw and let it idle untill just coolant only is coming out of the bleeder.

Originally Posted by Fivefingerdeathpunch

yes car must be running. it must get to proper operating temp, so about 10 min at idle should do it, open the screw and let it idle untill just coolant only is coming out of the bleeder.

There is a nut that I loosen first and then back off the screw...correct?

yea that nut on top of the thermostat houseing, just loosen that about 1-2 turns, then leave it and then you just wait.

Originally Posted by Fivefingerdeathpunch

yea that nut on top of the thermostat houseing, just loosen that about 1-2 turns, then leave it and then you just wait.

what about the screw?...

that nut on top is the screw/nut, thats all you need to do, is just turn it a few times and it opens up to let the air out.

my bad for not explaining.. i thought u bled it before.

Originally Posted by Fivefingerdeathpunch

that nut on top is the screw/nut, thats all you need to do, is just turn it a few times and it opens up to let the air out.

****I tried this and the unfortunately, it has not resolved the problem. Not sure what else can be done***

try thermostat next.

Do I have to drain the radiator first?

Replaced both thermostat and coolant temperature sensor below thermostat housing. I had to use a 19mm long box end wrench to get at it. Needed also to loosen dog leg for more room. Bled the system for about 15 minutes. There is less fluctuation in the temperature gauge. It hovers around the normal operating mark. When I stop at a red light it might rise about 5-7 degrees but it settles back down when I resume driving. I removed the rad cap and the fluid was right at the top. I might bleed it one more time tomorrow to see if I can get it to not fluctuate at all.

raising a lil bit when car is stopped is normal.

Originally Posted by gtpinsc

raising a lil bit when car is stopped is normal.

***Alright, but it still moves up and down a little (+-5 degrees). It could be that I am more aware now than before...It seems that before for the most part, the gauge would just sit in one spot after it reaches operating temperature..I will bleed it one more time.***

Everything is back to normal. Temperature gauge is reading normal again. The only time it rise above normal operation temperature is first thing in the morning. It rises from 158oF to about 194oF, and drops back to 158oF. The thermostat is 195oF. I suspect that it must have opened which resulted in the drop back to normal operating conditions.

P.S. I did bleed the system again. Guess it must have helped. I am going to hold off on replacing OEM radiator. I will do it only as preventative maintenance in the next 2-3 months. I have never had a problem with the original factory radiator (no leaks or overheating etc....). My only motivation to replacing rad was due to gauge fluctuation.