kraftada

Help!
Brand new build dart block etc 500hp
c3 81 dewitts radiator with dual spal fans.
fan switch 195/175 in the rad
160 t-stat
Heres what I have going on:
idle it at 180 degree all day, gauge sensor in pass head
down the road at 60 or so builds heat gauge climbs past 220+
fans not coming on. Pull over and withing a minute or so fans kick on
and temp drops.
No heater core no hose from pump to rear manifold

Any suggestions greatly appreciated.

Dynra Rockets

Have you called Dewitt?

Smells like a thermostat issue to me.

69427

Shouldn't the fan switch be in the head, not the radiator?

Gotta agree with Dynra. Is the thermostat choking off the coolant flow?

kraftada

dual spals ran off of switch in rad at fluid entrance. Some how it appear to me fluid is not moving, im leaning toward stat as well.
switch is 195 on 175 off. gauge sensor is in drivers head which show heat climbing down road at 55-60, it will slowly creep up too hot but fans arent on. Im thinking stat doesnt open all the way. but some off the fast drops seen after stopping and idle for a minute certainly adds some confusion.

v2racing

I would agree that the fan switch should be in the head.

Do you have all the weather stripping in place on the top of the radiator support for the hood? Is the radiator support sealed down both sides? Do you have the radiator sealed to the radiator support? Is your lower rubber fairing in place? If not yes to all of these questions, it could be an airflow issue.

Are you sure all the air is out of the system?

Mike

69427

I agree. One thing (and I've never actually witnessed this issue) that gets mentioned on occasion is the lower radiator hose collapsing at higher engine RPMs, reducing the coolant flow. (I'm still trying to figure out the conditions that would allow this.)

kraftada

no to the radiator sealed, not at the top, fresh air over the top, dual spal fans supersede any air flow issues. Lower hose steel coil no collapse.
Not sure if air is trapped.

3X2

Are the fans puling air through the rad towards the engine? i.e. not pushing air forward as in rotating the wrong direction or maybe pitch of fan blades reversed? Depending on the fan controller determines where the probe is mounted. I use a C6 fan and shroud in another application and the probe goes into the rad fins on the cold side of the rad, it doesn't use a sensor that sees coolant flow.

fishslayer143

sounds like the T-Stat is not opening properly,either not at all or just a small amount, allowing no hot coolant to flow to radiator which in turn doesn t tell the fans to come on.. you stop and T-stat finally opens or enough coolant gets thru to turn on fans

jb78L-82

What kind of water pump are you using?

My Stewart Stage 2 aluminum water pump requires a modified Robertshaw thermostat and will cause what you are describing with a normal theromostat.

I too think either way you have a thermostat issue (change it) or air in the system (not likely). I too have never seen the collapsed lower radiator hose issue personally and like others am still trying to logical understand that whole phenomenon......

FWIW-I too have had dewitts radiator now for about 10 years and it worked beautifully with the OEM L-82 and with zero issues I am using it now with the rebuilt/modded L-82 355 with 450 HP with the mechanical OEM fan and not the best seals around the radiator (most are original). The temp never goes above 180 degrees regardless of the temp outside or how it is driven....

kraftada

[QUOTE=jb78L-82;1595152815]What kind of water pump are you using?

My Stewart Stage 2 aluminum water pump requires a modified Robertshaw thermostat and will cause what you are describing with a normal theromostat.

I too think either way you have a thermostat issue (change it) or air in the system (not likely). I too have never seen the collapsed lower radiator hose issue personally and like others am still trying to logical understand that whole phenomenon......

FWIW-I too have had dewitts radiator now for about 10 years and it worked beautifully with the OEM L-82 and with zero issues I am using it now with the rebuilt/modded L-82 355 with 450 HP with the mechanical OEM fan and not the best seals around the radiator (most are original). The temp never goes above 180 degrees regardless of the temp outside or how it is driven....[/QUOTE

Thanks everyone for helping.
I went with the easiest thing to try:
Switched the t-stat.
Was a 180 stat put in a stewart 160.
Car warmed up to 160 gauge in head, and never moved from that except small spike after coming to stop after 60mph cruise. Just 5-10 degrees for a moment. However, although cooling has stabilized, I feel it is too cool. Will purchase another 180 stat.
THE PROBLEM, THE TERMOSTAT::::::::::::::::::
Again thanks all!

Big2Bird

At high RPM, the suction side develops low pressure. Unlike a thick walled vacuum line, the thin soft hose will collapse, then open back up at idle. Therefore, there is no tell tale sign.

george2066

after marker generic sender into oem gauge? do you have original stock sender that goes in intake near top rad hose? I think gauges and senders are calibrated to each other
I would also hunt down a Mr Gasket radiator cap that has a temp gauge built into it for another visual under the the hood
I fill the block thru the t-stat, top heater hose off(fill that hose) then drop in t-stat, connect heater hose, top off radiator, fill the reservoir.

was that the first run?

squeeze top rad hose, sound like water in it

the radiator fill and top of radiator is over an inch, so if fan sensor is up top by hose inlet and not sensing the water temp, maybe

my flexalite fan controller probe is up top near top inlet. I want the fans to sense the radiator temp.

fishslayer143

[QUOTE=
THE PROBLEM, THE TERMOSTAT::::::::::::::::::
Again thanks all![/QUOTE]

hmm, now where did I hear that? lol..

jb78L-82

oh I get that but millions of other cars on the road have the same setup with no collapse without a spring.....

Big2Bird

It is more prevalent with longer hoses.
Montes, Chevelles, Cadillacs come to mind. Remember the long hooded cars, with 3' shrouds and 6' hoses?
They all had springs.

This guy has a listing for NOS GM springs. Fits 887 cars.

http://www.ebay.com/itm/54-55-56-57-...19.m1438.l2649

chevymans 77

partially plugged radiator and efficient pump with no bypass system in place.

Neal

mrichi

You could take the thermostat out and try it like that . A 500hp engine is going to put out a lot of heat. What RPM is your engine at highway speeds ?

I fitted a 1979 front spoiler extension which is about 4" deep and made of heavy duty rubber belt ,that reduced my engine temp on the highway considerably.

Also make sure there are no restrictions on the exhaust side like blocked old cat converters

Finally the best mod ever was fitting a TKO500 transmission which dropped engine revs and the temperature

bmans vette

Thermostat test is so simple.
Pull it out and put it in a pot of water on the stove turn on the heat and if you have a meat thermometer put it in the water alongside thermostat.
Watch as water comes up to boil.
Note if the thermostat opens all the way and at what temp it opened at.

I drill 2 ea 1/8" small holes into the plate that moves on the thermostat before installing it. That eliminates any air trapped behind it.

Good luck