gixxertsi

iTrader: (6)

Having trouble with my 98 z28 running hot and I am starting to run out of ideas. The car was running at around 235 so I started to look into a fix.

1st tried bleeding the coolant system, no fix.

2nd replaced that t-stat, still no fix.

3rd replaced the water pump thinking it had to be the problem since nothing else worked.

Just filled the coolant and ran the car trying to bleed the coolant and still getting hot. Now its even running hotter than before.

To me it seems like the t-stat is not opening because the coolant level in the radiator does not go down when it reaches operating temp. So I'm now thinking I bought a faulty t-stat and replaced a working water pump or I'm over looking something.

Any ideas?

Stone17

iTrader: (3)

Remove the t-stat and see what happen.

LS6427

iTrader: (2)

Remember something for the future.......water pumps ALWAYS pump coolant, they just spring leaks because the seal goes. So you changed a good water pump. There is a 1 in a million chance a water pump will shear a shaft, then water will not move. So rare though.

I put my t-stat in a pot of water a couple days ago to test it....try that. See if it opens at the right temp, use a cooking thermometer held next to it while its in the water as it gets hotter.

Also, how do you know it was at 235*F??? Scanner or just looking at the gauge?

.

Metal Muscle

Is your fan working?

senicalj4579

iTrader: (41)

Its not uncommon for stock settings car to get 235 in hot weather. We dont really have enough info.

wssix99

iTrader: (5)

Is it ever going above 235? If not, it could also be something simple like blocked airflow over the radiator (dead squirrel, etc.) or the fans.

gixxertsi

iTrader: (6)

I am using the stock guage for temp. I noticed some coolant under the car over the last couple of weeks, not alot but a few drops here and there.

It usually runs right at 215 and has rarely gotten over that, but in the last week it has started to run warmer every couple days up to about 235 before I tried to bleed it the first time.

after that I replaced the t-stat and now it seems like it will not bleed at all. Its almost like the t-stat is not opening. I'm going to try and boil the t-stat when I get home from work tonight and see what happens.

Oh and now after changing the water pump and losing the coolant from the motor it just keeps getting hotter until I shut it off. Also no change in level of radiator at any time.

Fans are working fine and no blockage of the radiator

wssix99

iTrader: (5)

Did the coolant leaks under the car stop when you changed the water pump? (Your old one may have been weeping.)

Did you replace the radiator cap? If you aren't keeping pressure in the system, that could cause you cooling performance problems.

Do you still have the vent line going from the throttle body to the radiator? If you modded that out, it could make bleeding more difficult.

Aside from that, testing the thermostat is a good idea. You may also take a measurement of the true coolant temperature to see if your coolant temperature sensor is lying to you. (Since its really the only thing giving you an indication that there is a problem.)

gixxertsi

iTrader: (6)

Not sure if the leak stopped after the water pump change. I just did it last night, but it doesnt seem like its leaking anywhere from what I can tell.

Havnt replaced Rad cap, been trying to bleed the system right now so it has been off most of the time. It seems like the coolant is just not getting past the thermostat into the motor. No hot air comes out with heater on even when temps read high

I do have the tb bypass mod, should I do something to with that to make the bleeding easier?

Also just tested the new thermostat which I had in when I changed the water pump and it works perfectly in boiling water.

Not to sound ignorant but if I wanted to take the true coolant temp. where would be the best place to test it? and would using a cooking thermometer work?

Fosnot

iTrader: (15)

When you replace the coolant did you make sure to fill the top of the engine?
If not take the hose that attaches on the drivers side of the radiator, off the radiator side, and fill the black/hose to the brim, reattach hose to radiator.


When you replace the thermostat it drains the block, and without coolant to kick the thermo-actuator, no fluid is going to move. Just an idea, ik the same thing happened to me when I replaced the thermostat that jammed closed with a 180* one, once the block got topped back off viola! done.

gixxertsi

iTrader: (6)

Finally got it bled. Filled the upper radiator hose and its running right at 210. Prob didnt need to replace the water pump right now but its good piece of mind because I think it was starting to leak.

Thanks for the advise guys, I was lost there for a while.

wssix99

iTrader: (5)

My guess... is that your water pump seals were going bad, leaking coolant, and injecting air in to the system.

With a stock system, the car will bleed air itself and push it out to the radiator and on through the overflow system. If you bypass the TB, air can get trapped and cause issues.