binks0678

iTrader: (7)

98 trans am that i have on my lot. If it sits at idle for a while or cruising at a low rpm it warms up to about 235* (used a scanner not the guage). As soon as you rev it up or run it harder it cools back down to 210. No pressure in the cooling system so im thinking it has to be thermostat or water pump. Any input? also where is the thermostat on these car and how much of a bitch is the water pump change?

LS6427

iTrader: (2)

The water pump is fine....they only leak, they DO NOT stop pumping water.
DISCLAIMER....you could be the 1 in a million that has a sheared shaft.....but then you would overheat into the red zone in 10-15 minutes of driving.

What do you mean it has NO pressure.......?? Can you take it for a 30 minute drive, pop the hood and take the radiator cap off and no pressure is in there????

NOT THAT I RECOMMEND TRYING THAT............


Usually if you have heating issues at low speeds or city driving....the fans have a problem.

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binks0678

iTrader: (7)

thanks for the reply ls6427
i meant not like blown headgasket type pressure.....the fans kick on right at 210. As far as the pump if they will not completely stop pumping is there any way for them to get weak and not pump enough at idle? I just thought it was kinda odd that if you sit there and rev the motor repeatedly the temp goes down pretty quickly, then let it idle and back to 235 it goes.

LS6427

iTrader: (2)

First thing I would do....change the t-stat. Its cheap and takes 5 minutes to change.
***If you have a partially stuck open t-stat, which I had happen to mine last week, when you rev it more coolant will flow past simply because its ramming the coolant by the t-stat and helping it circulate and cool....but when it idles less coolant will be flowing by that partially open t-stat causing the temp to increase because of poor circulation. Maybe thats whats happening.***

The water pump will increase its volume of flow as rpm's increase.

Are BOTH fans coming on together...and do they go into LOW and HIGH settiings together? If they don't work TOGETHER all the time and at both speeds...something is wrong.

I would try a new t-stat......if thats not it, you can just return it for a refund......10-15 minutes of work to rule that out and your money back. Just clean it real good and tell them it didn't fit.

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LS6427

iTrader: (2)

Also....allot of people will tell you that 235*F isn't something to get concerned about.

Hell if I'd ever want my engine running that damn hot................I drove around yesterday and the day before with my new t-stat and purposely got the engine hot, with the A/C on the entire time. No way I could get higher than 216*F. Talking temp readings right on the head, brass temp sensor and the coolant line coming right out of the head.
If I cruised steady and then pulled over to check....temps were hanging around 188*F and 198*F.

Thats how I like it.

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binks0678

iTrader: (7)

alright sounds like a plan ill run to the store and grab a tstat. Hope they have them in stock! Im honestly not sure about the low and high fan settings (I really didnt know they had 2 settings ) But ill check that also. Thats kind of what i was thinking about higher rpms "raming" coolant through a partially stuck tstat.

LS6427

iTrader: (2)

Also.......these cars are getting up to 10-14 years old............an often missed part of maintenance is cleaning the a/c condensor in front of the radiator. They get dirty as hell and all kinds of road debris clogs up the surface area.

Mine was about 50% clogged with debris after 5-6 years. It was ridiculous what I found in there. I cleaned it and I ran ALLOT cooler. Actually, if I turned the a/c "on" I would straight up...overheat, nothing I could do except except shut the a/c off to cool it down.

So again....if its dirty as hell it might not get that suction of airflow by the fans at idle or in city driving......but once that ram air is rammed up in there while the car is moving..might help cool it down.

Pics of mine below.

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O2Form

!st thing is replace the rad cap................

LS6427

iTrader: (2)

Unless he left out that coolant was boiling over or low.....ain't the cap.

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binks0678

iTrader: (7)

Update i got some more time to work on the car today (been busy as hell lately). Still no luck on her, checked fans they both go into high and low setting at the same time. Changed the thermostat, and topped off coolant. Started her up and let it run and sure enough starts creeping back over 210. This time around revving it did not cool it back down. So got under the hood while it was running with both fans on high setting, both radiator hoses feel soft and cool to the touch, the radiator feels cool, and the fans are blowing cool air. So clealy my coolant is not circulating. Tomorrow i am going to try a different thermostat but if thats not it then it would have to be water pump or a blockage right??

joecar

Or trapped air.

LS6427

iTrader: (2)

Listen..........
-start it up when COLD with the radiator cap off
-while you are standing there waiting for it to warm up...squeeze the upper and lower radiator hoses rapidly and firmly 20-30 times each. Go back and forth 3 times to each hose. This will move the air bubble past the t-stat allowing hot coolant to touch it, allowing it to open and let coolant flow through.

If that doesn't work, the t-stat is not opening.

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O2Form

did you change the rad cap?

Its gonna cook over if its not holding full rated pressure.