1970 Deville - 472/500 What temperature thermostat?

[chrisntam]

It appears from the factory, the 1970 cars used a 180 degree stat.  I have a 195 stat in there now (Marty/MTS recommended the 195).  I think the motor runs a little warm, but I'm not 100% sure.  My temp gauge detects metal temperature at the bolt holding down the t-stat housing.  The metal temp running down the road is about 215.  I have no idea what the water temp is, don't have a gauge in to detect water temp.  Once it gets to operating temp and while idling at a stoplight, the metal temp creeps up to 230 or so.  I have an IR temp gun, the exhaust manifolds and heads are 500 degrees plus (my gun only goes up to 500).  I can't recall what the upper and lower hoses are, but checking the bolt where the temp sensor is shows the temp showing on the gauge is about right.  New four core radiator, 5 blade factory fan (no clutch) and a "Flow Kooler" water pump.  So I wonder if I should put a 180 degree stat in it.  What benefit is a 195 stat?  I've never experience a boil over or anything like that, I'm just not used to (yet) this metal temp gauge and am moderately uncomfortable with the temp it is showing.   I have a factory sender in the stock location for the idiot light and a metal temp sensor as well, neither have lit up.  It is a newly rebuilt engine with less than 200 miles on it.

As a side note and as a companion question to the oil pump thread, the "Flow Kooler" water pump and the oil pump only have about 1/8" to 1/4" clearance between the two.  So tight I could barely get the lower hose on.  Any one ever have that issue?  It's like the water pump lower hose outlet isn't angled out enough.

And another thing............unlock the '53 Eldo thread! 

Your thoughts?

[Scot Minesinger]

The shop manual prescribes 180'F thermostat and I would use that.  Keep in mind the thermostat regulates minimum operating temperature.  If you drive in a real cold climate I could see the 195'F thermostat.  I guess it really does not matter too much.  My car has the 180'F thermostat and operates in 195'F to 205'F range most of the summer.

[Scot Minesinger]

Chris,

230'F is too hot.  Generally with 90'F weather it should be in the 200'F range I think at idle at a stop light.  If it is 95-100'F with a/c on and idling in slow traffic for an hour, OK 115'F or so, but 230'F is up there. 

My 1970 ran hot once after had the 4r radiator - check your shrowd.  Make sure no air is passing around the radiator on sides and bottom - visualize the air flow thru the fan and make sure it all must be drawn thru radiator, not any around.  That rubber piece on the bottom of the radiator is important.  I did change my five blade fan out for a seven blade commercial chassis fan, and it does provide more air flow.

It goes without saying all your timing, fan belt, and everything else is good. 

Make sure your snorkel damper is open to draw air from engine compartment (use flashlight in snorkel blade should be horizontal) and not drawing intake air in warm up mode across exhaust manifold.  This set up fails in the draw air across exhaust manifold mode because heat switch fails in open position.

[chrisntam]

Thanks for the replies Scot.  The wild card in this is what should the metal temp be?  Is it safe to assume that if the water temp is say, 200, the metal temp is the same?  I'm thinking I may put a 180 stat in it and while I have the system drained, I'll install an actual water temp gauge.  I also think I'll install a 7 blade fan as well.  Will probably just get an aftermarket metal flex fan as opposed to hunting down one from an Eldo.

[TJ Hopland]

I wonder if tending to run warm was one reason they went to a light instead of a gauge?   I have had a lot of cars I drove for years happy as can be.   I then decided to put gauges in and from then on just stare at the gauges and worry.   Probably also why many of the factory gauges don't have numbers on em,  just a C and F. 

The 472/500 seems to make a lot of heat so they need 100% of their cooling system capacity.  At this age it can be difficult to maintain that capacity.   There are dozens of things that could be causing a reduction in efficiency, could be something as simple as some of those rubber flap things missing from somewhere under the hood.  Airflow is way more complex than most people think.   

The stat these engines use is overall a pretty common physical size but where its different is its supposed to have another disc valve at the bottom that closes off the bypass circuit when the main part of the stat opens.   I'm not sure what percentage of cooling you loose if that bypass is open but it was apparently enough that they bothered to design it so the stat would close it.  I think I took apart 2 or 3 of these engines before I found one with the correct stat and I have got them without that disc from parts stores.   I have always fixed / changed other things at the same time when I have swapped a non disc one to a disc one so I can't say if the disc was the magic or some other repair that made the difference. 

I too have a gauge that uses metal temp under the bolt.   I ran it for a while with my old mechanical gauge and they seemed to agree maybe +/- 5.  If I point my IR gun at the sensor I read higher (I think) than the gauge so apparently in my case the gauge is calibrated knowing that the metal temp won't be exactly the coolant temp.  If I point the gun at other water parts of the block up front or the hose just after the stat it agrees with the gauge. 

Modern antifreeze seems to develop a clear goo layer inside the system.   This goo seems to thrive in things that don't get real regular driving and according to an old time radiator shop its difficult to remove and acts as an insulator.   Looking down through the coolant I could not see it in mine but after I drained it and it was on the shelf for a while it did kinda turn crusty. 

The other thing that the radiator shop guy pointed out is that over the years the copper radiator makers have got the fins thinner and more spaced out.   Mine was an early 1990's Modine one that I thought was pretty good but the guy showed me the 'standard' core material he uses on rebuilds, it has at least twice the fins. 

[Scot Minesinger]

Do not install an aftermarket flex fan.  I did that, and it was promptly replaced:

1.  The fan is extremely loud, at 60mph unbearable - Great audible tachometer though.
2.  Those are made generally not high quality, and my mechanic friends said they have seen them come apart at 3,000 rpms, and it basically cuts the front end of the car off.  Those stainless blades are at high velocity and if they let loose it is a disaster - your car is badly damaged.

DO NOT INSTALL AFTERMARKET FLEX FAN

[Scot Minesinger]

I did install gauge and drive my car regular, it has 124k miles on it now and engine was re-built.  Highly recommend the temp, oil press, volts, vacuum, and tach gauges.  I replaced the sensor under compressor that activates light with temp gauge sensor.  You still have the "hot block" warning light.  Never tried but, you could remove your ported vacuum switch and put the sensor there and retain all original warning lights. 

[EAM 17806]

CHRIS!  "STANT" Company lists a 195* degree thermostat for the 1970 Cadillacs as original equipment. Their part number is #13459 for the 195 and #13458 for the 180* as an alternate thermostat.  Check it out; I would use exactly what the factory recommends.  EAM

[Scot Minesinger]

It does not matter.  Your car as is will operate at 230'F if it has a 150'F, 180'F, or 195'F thermostat-the thermostat controls the minimum operating temp, not max.

1970 Shop manual calls for a thermostat that starts opening at 182'F and is fully open at 205'F.  I equate that to a 180'F thermostat, not 195'F.  A parts catalog is not a reliable source of information. 

Look on e-bay under 1970 Cadillac parts and witness hundreds of wild interpretations of "fits 1970 Cadillac", which usually means with a reciprocating saw, sledge hammer, numerous crazy modifications and pry bar the part may be able to be installed.

[mgbeda]

For what it's worth I've been running a 180 deg stat in my '76 (195 was original) for 30 years and never had an overheating problem.  I also changed over the 195 stat to a 180 one in the '75 Buick 455 I got three years ago and it also seems to like the lower temperature better.

-mB

["Cadillac Kid" Greg Surfas 15364]

Chris,
Not to pipe in here late, but there are two things that I see. First is that there is an exponential difference between a 5 bladed (factory) fan and the 7 bladed ones used for HD cooling and AC.  I know this from personal experience here in Southern Texas.  The difference really shows up in traffic and slow speeds where all the air flow is dependent upon the fan.
Secondly, These (472/500) motors were designed to run warm in order to run efficiently.  The higher temperature thermostat gets the engine up to operating temperature quicker, and although it is counter intuitive, colder is not necessarily better.  When I bought my 72 Eldo new I was concerned about the (perceived) high temperatures, so I put in a water temperature guage.  After freaking out at seeing 220-235 degrees most of the time and being told by the dealer that was normal, I took the gage out. For conversation sake, knowing your year does not have this device, but the 71's and for a few years, have a vacuum control device that allows full manifold vacuum ABOVE 230 degrees, and is part of the normal operational envelope.  Not a Chebbie.
Greg Surfas

[Scot Minesinger]

Chris,

Yes use the 7 blade factory Caddy fan that was std on all commercial chassis.  It provides more air without noise and risk of destruction, unlike JC Whitney/Summit fans that make you deaf and risk slicing your car in two.

The 1970 has the switchover to run vacuum advance and speed up idle at 220'F.  After I changed the intake manifold out the timing was way off for a week before I re-set it to factory and of course car ran hot, especially at idle.  The car does not like 230'F.  Maybe the retarded timing made this more apparent.  Now that the car is timed right it runs cooler. If is 95-100'F w/ a/c on, idling for a while and car gets to 215'F it does still run perfect.  Seems to be better at plus 205'F - 210'F than 180'F I agree.  The 180'F stat starts opening at 180'F, it does pop full open at 181'F and close at 180'F.  Does not open all the way for a good 15'F or so at least -these are not precision made for a rocket ship and calibrated by NASA - they are made in China for a dollar a piece.

The 71 and newer may run better at 230'F.   

[chrisntam]

Where would a kind sole such as I find a factory 7 blade fan?  eBay?  In the parts wanted section here?

As a side note, I abandoned the temperature controlled vacuum switch (ported vacuum switch) and associated vacuum lines and am now running straight ported vacuum to the distributor.

My vacuum lines are as follows:
1) manifold vacuum to the brake booster
2) manifold vacuum to the trans modulator
3) ported vacuum to the vac advance
4) manifold vacuum to the PCV valve.
5) carb vacuum to the choke pull off.
6) manifold vacuum to the heater/ac system

Am I wrong to abandon the PVS?

["Cadillac Kid" Greg Surfas 15364]

Chris,
You might call Honest John's over in Denton.  The 7 bladed fan cam on EVERYTHING (NOT JUST CC) with AC and HD cooling from 1966 through at least 1973. Scott with all due respects, no one said the cars are supposed to run at 230 degrees.  The example was for a later vehicle, and what the factory had figured as an upper edge of the operational envelope.  Scott if your engine was retarded enough to run that hot it is a testimony to the structural integrety of the motor itself that (with 10+:1 compression and your camshaft (stock timing) that you did not destroy something while driving.
Greg Surfas

[chrisntam]

Thanks for all the insight gentlemen!!

I'd want to find a fan that doesn't use a fan clutch, that was one year only ('70), right?

[The Tassie Devil(le)]

I run full manifold vacuum to the distributor on my '72.

Got rid of all the anti-pollution garbage, including the AIR Pump, and it runs sweet.

With full Manifold Vacuum to the Distributor, it really livens up the engine.

Bruce.

[Scot Minesinger]

Greg,

Everything you wrote is right on the money, I agree 230'F is for later year cars, and the car running hot for 10 miles or so is testimony to a rugged engine.  I really like the 472/500 engine.  The 1970 Cadillac was standard with five blade fan, I have three and the shop manual collaborates my five blade fan post.  The 1969 had a fan clutch and 7 blade fan.  The 1971 I do not know (I will go with what you wrote 7 blades).  The 1970 had a 5 blade fan and no clutch, and it was claimed to flatten out at speed.  This is nice because you don't have a fan clutch to fail, although they are durable.

I think they did this in 1976 too, Cadillac did not have a fan clutch in 76, but did in 75.   

Cadillac King, Honest John, USA Parts are all sources of the 7 blade 1970 commercial fan, cannot quite remember where I got my two, think it was USA Parts (but they sourced it).

[Jeff Rosansky CLC #28373]

What is "ported" vacuum?   I haven't change a single thing on mine.....actually I assume it is correct but haven't even checked that. 
Is there something that most of you in the know recommend we modify.  I have a 70 also.
Jeff

[The Tassie Devil(le)]

Ported Vacuum is where the vacuum source if from the port on the front of the Carburettor, and is partial vacuum, and not complete full vacuum all the time.   This is designed for Anti-pollution stuff.

Full Manifold Vacuum is from a port on the top of the actual Intake Manifold, and is there all the time.   A constant source.

Ford vehicles use Port Manifold for their Vacuum Advance, and their distributors are set up for that, but GM Distributors are designed for full manifold vacuum.

I always find it funny when I see a Holley Carby on any GM engine, and the vacuum advance is connected to the side of the body, as it is when on a Ford.

Bruce.

[Scot Minesinger]

Jeff,

Fairly certain I have a factory comprehensive vacuum hose diagram for a 1970 Cadillac.  This was published subsequent to the shop manual by Cadillac and it is very handy.  If you want, I can run you a copy if I have not already (cannot remember) - send me your address.  Then you can check to make sure everything is hooked up correctly.

Scot