C Murda

iTrader: (24)

so finally got the motor in the new chassis and i filled up the radiator started it up had the heat on full blast and the radiator cap was off but it seems as f the thermostat doesnt wanna open up?? everything was working fine when the engine was fist pulled out. now while the car is running its begins to overheat and the radiator seems to fill up and overflow out...then when i shut the car off the radiator is like half full and if i top it off when i start the car up again the minute it begins to go past "210" the radiator will overflow again... if i start the car without topping the radiator off then the fluid inside will rise but not overflow and the car will REALLY overheat then i HAVE to shut he car off....

im not sure but if i remember correctly i thought the lower radiator hose is where the hot water is supposed to coe out of while the upper is were the cooler water is supposed to be sucked in??? if so then why is my lower cold to the touch and the upper is EXTREMELY hot???


EDIT also my heater doesnt seem to want to blow hot either?

crainholio

iTrader: (2)

Remove the upper rad hose from the radiator side and pour coolant into the engine via the open hose end.

Old smallblocks regulated temp by a thermostat that didn't let coolant *out* of the engine...

LSx engines regulate temp by a thermostat that doesn't let coolant *in* to the engine. Big difference.

You therefore want to fill the engine, so the stat will see heat as the engine warms up and open properly.

C Murda

iTrader: (24)

Hmm I'll try this when I get home from work thanks

crainholio

iTrader: (2)

PS: You may already know this, but don't be adding coolant to the rad when the engine is anywhere near operating temp unless the engine is running, cracked block is a show-stopper.

sjsingle1

iTrader: (1)

dont forget to let coolant bleed from the front crossover tube........works for me every time

DaddySS

You may be over thinking this. If the water at the bottom hose remains cool while the upper is hot it is a classic symptom of a bad therm or clogged radiator. It doesn't sound like the latter so why not replace the therm?

crainholio

iTrader: (2)

A block w/ cooling jackets full of air causes the same symptoms, and for the same reason...thermostat isn't open. In this case it's because there's no hot coolant present at the thermostat to actuate it.

DaddySS

I don't necessarily agree but it doesn't really matter. Whether it's air or a bad thermostat it's not flowing so he can try putting coolant in as you say, if that doesn't work, change the therm.

LS1-450

iTrader: (33)

Don't forget to run it for 10 minutes w/ the heater on high, a couple of times. This will purge air from the heater core.

+1 on filling the top radiator/water pump hose so that coolant gets into the block. This is a biggie.

bww3588

iTrader: (49)

the thermostat is in a different location than what you are thinking....if everything was working fine when the engine was pulled, why would it just quit over the build?

if it were in the traditional location, hot water would be pushing against the t-stat causing it to open, where it is in an LS1, the only water touching it is cold.

cutlass_455

iTrader: (2)

I ALWAYS, drill a couple small holes in t-stats. 2 1/8 holes guarentee that you are gonna get water and air thru there. Even just when you are pouring the water then you can tell its getting past it. I'd try that for sure.

C Murda

iTrader: (24)

Thermostat is new with 20k on it and the raadiator is a new griffin so I know it's not clogged...must be air I didn't pour anythig down the top hose so hopefully this will work

The Alchemist

iTrader: (19)

Another vote for cracking open the vent tube on the front of the heads. I do beleive it's the driver's side that you need to purge to vent the air out. I know the last time I helped a buddy swap heads, we topped off the coolant with the car cool including the overflow. We started the car and then cracked open the vent tube and withing 1-2 minutes water started to bubble out of the vent hole. It bubble for another minute or so, then I closed it went it became a steady flow. Let the car come up to temp, and then checked everyting and all was good.

5.3LJimmy

iTrader: (10)

Fill from the upper hose as mentioned, make sure you have water in the overflow jug and the radiator topped off, run the engine to operating with the cap on, shut the engine off and let it sit for 10 minutes(you will hear the water being pulled in from the jug), carefully remove the cap from the radiator and refill it and the overflow. Repeat until the water level stops dropping, which usually takes three or four times. It is not required to have the heater on while you do this because f-bodies don't have a heater by-pass valve.

C Murda

iTrader: (24)

ok so i tried fillin up the motor through the upper hose and started the car...still nothing it went wayyy too hot and it seems as iff the upper radiator hose is the only one getting hot meaning the motor is pushing water through the upper hose???? but this only happens when the car is getting hot and then start overflowing out my radiator. the lower one is still cold to the touch. what the hell is goin on?

5.3LJimmy

iTrader: (10)

If you filled the block and it is still doing that I would change the thermostat.

crainholio

iTrader: (2)

Amen, time for a new thermostat. Somebody mentioned drilling a hole, I do this also. 2 small holes in the flat surface, maybe 3mm diameter, on opposite sides of the mechanism.

C Murda

iTrader: (24)

Well I think the thermostat was just stuck cause I decided to rev the engie to 4k and held it there then all of a sudden my het was blowing HOT and temp gauge began to drop to my normal opperating temp...

joecar

It wasn't stuck, it just wasn't getting hot coolant.

See the attached pic, read the note on it regarding the bypass valve when the TS is closed (the blue note).

When the TS is closed, the BP is not open, it takes at least 5 psi of pressure differential to open the BP...

when you revved up the engine, the WP created enough pressure difference, the BP opened sufficiently to allow hot coolant hit the TS and displace colder coolant out of the TS pocket.

The BP has a hole thru the center of it, but coolant will not necessarily flow thru this hole while the TS is closed (i.e. the hole is like a dead end).


The fact that the TS opened after you revved could mean that your heater core/hoses may have been blocked or full of air...
the heater circuit is what initially supplies hot coolant to the TS before the TS has started opening...

while the TS is closed, the heater circuit is the only flow past the TS unless the BP valve opens.

joecar

But do keep an eye on the TS, if it plays up again replace it.

Edit: actually I meant drill a hole in it.