Robert Shaw Thermostat Problem

Robert Shaw Thermostat Problem

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By oldcarmark - 8 Years Ago

I just finished upgrading the Cooling System on my 56. Nice new Water Pump, 5.5 Inch Water Pump Pulley, Aluminum Rad, 6 Blade Fan, Plug in the Bypass Hose, and a Genuine NOS Robert Shaw Thermostat. Everything works and no Leaks( hopefully) EXCEPT the Thermostat. Its like no Stat at all. Water is flowing into Rad as Engine warms up. It maxes out at about 120 Degrees.
This is the same thing I experienced a few Years ago with 2 Mr. Gasket Stats. Put a conventional 160 Degree Stat back in and everything is good. I did test it in Boiling Water and then in Cold to make sure it closed. Worked as it should. I have heard of these sticking closed but not open. Any Ideas?

By 62bigwindow - 8 Years Ago

I did the same boiling water test on my Robert Shaw thermostat. Then I noticed my engine just wouldn't get past 140ish with a 180° thermostat. I took it apart to put in a 190° and discovered the t stat was broken and stuck in the open position.

By oldcarmark - 8 Years Ago

62bigwindow (7/28/2017)

The One I had trouble with previously I still have and retested it in Hot and cold Water. Still opens and closes as it should. This is the third Time I have tried using these type Stats and all 3 did the same thing? I am at a loss to understand why these type Stats don't work and conventional Stats work fine. And before someone asks-Yes it is in the correct way with point facing towards Radiator.

By oldcarmark - 8 Years Ago

I just put the Conventional 160 Degree Stat back in and it works properly. I don't know how the Robert Shaw Stat is being bypassed and not working. I have ordered one of the Napa # 6 Stats and see how that works.

By GREENBIRD56 - 8 Years Ago

Mark - Do you have these new t-stats drilled for the 3 bypass holes? I expect a fair amount of water to go through them when the engine is cold - when there is pressure on one side and no back pressure. It should be enough slow the warm-up process. If you've got the flow increased by the smaller pulley - and more air moving with the six blade fan - cooling equilibrium is going to be a bit different than before.

By oldcarmark - 8 Years Ago

I drilled it Steve. I tested it afterwards to make sure it opened and closed hot and Cold. There's hot water going into Rad within 2-3 Minutes as it warms up. Take it for a drive which should bring it up to at least 160+. Nothing. It goes to about 120 and stays there. Never gets near 180. Same thing I experienced all 3 Times I have tried these. Even with the regular 160 Stat the cooling System is much better. Temperature is more level at about 160. Stop at a light and it doesn't change. Before the Temp would start to move up when stopped. On the right Track. Just wish the Stat would work properly. Even if there is a fair amount going through the drilled Holes it should still regulate minimum Temperature when driving and its not. Previously I tried these without the Holes. Same thing. Never warmed up to operating Temperature.

By 2721955meteor - 8 Years Ago

my 57 has temp gauge the left rear of the head and 1 at the intake at stat they are never the same. 1in the head measures the coolest part of the head 1 at stat measures the warmest part of both heads. my opinion you ar screwing up the whole cooling system. when you stop at a light if running a auto shift to neutral.you drop the load and torque cools down engine speeds up a bit. drilling the stat and restricting the bypass slows down the warm up.ys run the best at 180 at the stat nd as the stat opens slowley temp is controlled at ideal number. if you are in to summer or hot part of the land heating the whole system including the rad will not give you any reserve at stop lights or traffic. there ws a group who did a test on 57 bird and replaced all the shrouding and belting as was when new. had smaller pulley and 4bladed fan,un restricted bypass and had no issues. the better water pump for birds with the goofy spacers makes good sense. if you measure the temp rad at the top tank and the bottom withe a heat gun as long as there s 10 dgrs diference and huge at stat is under210 you are not over heating. if the top to bottom reading at rad has a greater difference the rad is restricted or pump is cavetting. 90% it will be rad issue. this is always a wild issue,especially with all we experts. WE THINK.good luck

By Gene Purser - 8 Years Ago

r rigid?

oldcarmark (7/28/2017)

Nice new Water Pump, 5.5 Inch Water Pump Pulley, Aluminum Rad, 6 Blade Fan, Plug in the Bypass Hose, and a Genuine NOS Robert Shaw Thermostat.

Would you share with us what brands of water pump and aluminum radiator you used to get such good results?
Edit: and is the fan a flex or rigid?

By oldcarmark - 8 Years Ago

quote]Gene Purser (7/30/2017)

oldcarmark (7/28/2017)

Nice new Water Pump, 5.5 Inch Water Pump Pulley, Aluminum Rad, 6 Blade Fan, Plug in the Bypass Hose, and a Genuine NOS Robert Shaw Thermostat.

Would you share with us what brands of water pump and aluminum radiator you used to get such good results?

[/quote]
I got the Rad off Ebay from Patriot Cooling. $225.00 Approx. Made in Chine. Ships from California. Seems very well made. Fit perfect with no Modification. 3 Row thicker than Stock. Has built in Transmission Cooler for Automatic. They seem to have One for most Applications.The Water Pump is a Cardone. I also added a 5.5 inch Diameter Water Pump Pulley and 6 Blade Fan Blade.

By John Didde - 8 Years Ago

where did you get the Cardone water pump?

By charliemccraney - 8 Years Ago

Cardone is a company that remanufactures all kinds of parts. As such, it is more or less a stock pump, available through most auto parts stores.

By oldcarmark - 8 Years Ago

They are also available as a new not rebuilt Unit from Cardone ( 58-200 New 55-21110 rebuilt) and also from Airtex (AW488). I changed mine while I had it apart because its at least 20 Years old and only a matter of Time before it would have let Me down.

By 2721955meteor - 8 Years Ago

standerd ford rad with new core on my 57. rad shops hear use some sonic system not good. as hot tanks not allowed,if they dismantle rad to rod the cores, a new core is little more $. as cores age they clog up..water pump is a exchange from local parts. same for the stat. champion cooling supplied atom. rad for my 49f1 pickup with 292 y. my 32 ford which i no longer have had a shampion rad and a 302 no issues with any of them. re my 57 we had had 85 dg temp still no heating issue

By John Didde - 8 Years Ago

I did notice one thing I am using a mopar160 thermostat with 3ea 3/32 holes drilled in it, also I have a blocked off bypass, problem
I replaced my temp sending device in the left side back corner of head it would go to zero on start up after 3 minutes of running
it would go to max, though I had a bad sensor, come to find out I have a hot spot in that area and I don't know how many more
after the thermostat opened it would go back to normal operating temp. With the cap off It would boil over as the thermostat opened, then go back
to normal circulating. I am going to open the bypass again and try that.

By CSPIDY - 8 Years Ago

Agreed, with the by-pass blocked there is no flow within the engine and will tend to get hot spots

By oldcarmark - 8 Years Ago

John Didde (8/1/2017)

When You changed Stat etc did You let it run with Cap off until Stat opened and let the Air in the System escape? I just did mine as you know with regular Stat( removed the Robert Shaw) and bypass restricted and had no problem. I have a Mechanical Gauge in front part of Intake( drilled Hole and Tapped) as well as the Dash Gauge. Both Gauges moved up as Engine warmed up.

By GREENBIRD56 - 8 Years Ago

Only specific trouble I've had, was with the 180º version of the Robertshaw style of t-stat. Didn't behave at all, the one I tested in the engine was inconsistent (as reported by others). With the 160º back in there - it all worked as I expected. The "leaking" (drilled) version slows the warm-up - and switching to the smaller pump pulley showed water flow before my temp gun showed enough heat to open the 160º t-stat.
Being sure the system is "burped" is sort of SOP I think - and the t-stat hole mods help to do that.

By oldcarmark - 8 Years Ago

GREENBIRD56 (8/1/2017)

I have tried 3 of the 180 Robert Stats and had the same problem with all 3. I have One of the Napa 170 Stats coming so I will see how that works out. Changing the Rad, 6 Blade Fan, and smaller Pulley has made a big difference already. Temp is much more stable driving or idling at a Light. Doesn't move much from 160 which is what the Stat in it is right now.

By charliemccraney - 8 Years Ago

I haven't had any temperature regulation issues with any Robert Shaw style thermostat USA, or Chinese. I've had 160 and 180 Mr Gaskets (China), 180 Milodon (USA). However, none of mine are modified with the holes

By paul2748 - 8 Years Ago

After many of the comments I took out the plug with the 1/8 hole in the bypass and everything returned to normal. I am not using a Robertshaw type thermostat and at this point do not plan to. I plane to do some engine work and am going to try the new space for Tbirds. I may go to the smaller pulley too. I really don't have a heating problem, but I want to make sure I don't.

By Lord Gaga - 8 Years Ago

paul2748 (8/2/2017)

I tried the plug with the 1/8" hole in the bypass too. The first time I got on it and wound out to around 5.500 RPM one of the heater hoses ruptured! A big mess! Just glad I was close to home. That plug is a bad idea.

By CSPIDY - 8 Years Ago

Lord Gaga, Did you drill the 3ea 3/16 holes into the thermostat? there has to be the ability for the engine to flow coolant before the thermostat opens, otherwise it is dead head pressure and the coolant in the engine is stagnant. this could also cause hot spots.

By GREENBIRD56 - 8 Years Ago

The cross sectional area of the bypass port is about .150 in² (so are the heater hoses if the valve is open) - anyone trying to put full output of a waterpump (at 5500 rpm) through it with a closed thermostat is going to get.........?? Sometimes I read things here that must have hurt.

I usually start my outfit - and let it run on the electric choke setting until it hits something like the t-stat setting - 160º. Haven't seen any evidence of the "hotspots - water seems to flow through the thermostat into the radiator at fast idle. What am I missing here?

By charliemccraney - 8 Years Ago

What condition were the hoses, to begin with? If pressure got high enough to rupture a good hose, then it should also have been boiling out of the radiator cap. Were the clamps sufficiently tight? Was the engine was up to operating temperature and therefore the thermostat was open before the 5500rpm sprint?

By Lord Gaga - 8 Years Ago

The hoses

charliemccraney (8/2/2017)

The hoses looked to be in good condition but I don't remember their age. The coolant was at approx. 180* for some time so I assume the thermostat (large hole type with 1 drilled eighth inch hole) was fully open. The clamps were tight, the hose split open. This engine is a 322" Y running a large shaft truck water pump with the small dia. truck pulley and a flex fan behind a '55 Caddie radiator. I'm glad the heater core held up! lol