1971 454 thermostat question

[Jim K.]

I have have a 71 big block that is running at a steady 220 degrees for all types of driving. Not bad, except it would be nice on hot sunny days to have it run a little cooler to keep inside temp down.
Will changing the thermostat help to reduce the temp. I just took out a 195 degree thermostat and the manual shows 180. Will putting in a 180 make it run cooler?, would a 160 make it run even cooler? Will Water Wetter help it?
The coolant I removed was orange, should I use the same or change to green?
Thanks, Jim

[John H.]

Re: 1971 454 thermostat question

Jim -

Changing to a lower-rated thermostat will have no effect whatsoever on operating temperature - the thermostat only determines MINIMUM operating temperature (like in the winter), unless your cooling system is capable of cooling the engine below the thermostat's rating in warm weather, which is rarely the case.

Step #1 is to make sure you have a problem, by using an I.R. gun to "shoot" your thermostat housing and comparing that reading to your temp gauge at the same time so you know what your gauge is really telling you; Corvette temp gauges are notorious for reading high, especially if the original sending unit has been replaced. If an I.R. gun shot confirms an accurate gauge reading, 9 out of 10 marginal cooling issues are radiator-related; nobody ever expected them to last more than ten years, and if the cooling system hasn't had regular maintenance (flush/replace coolant every two years), it doesn't take long to build up scale in the tubes.

Being something of a Luddite, I prefer the "green stuff", as its behavior is a known quantity after 50 years; GM is still up to their eyeballs in field problems with the "orange stuff", and I won't use it myself until those issues are resolved.

[Joe L.]

Re: 1971 454 thermostat question

John and Jim------

Yes, "the-thermostat-is-the-cause-of-my overheating" must be one of the more pervasive myths in the automotive world. I believe that it has its roots in "wishful thinking" on the part of car owners. In other words, thinking that if they can just replace this cheap and easy-to-replace item, then all of their cooling problems will go away.

Thermostats can and do fail, though. Since a thermostat is what amounts to a normally closed valve, when they do fail, they usually fail closed. This produces VERY rapid overheating, especially in cars not equipped with a bypass. In bypass-equipped cars a little coolant flow remains available and the overheating comes on a little slower. In other words, when a thermostat does fail, it usually does not cause a subtle problem.

[Dick W.]

Re: 1971 454 thermostat question

I have used the basic principal, if it does not boil over and lose water, 220 deg is permissible operting temperature... Getting a big block to run much cooler is a very tough task. Aux cooling fans will help a few degrees, but not very much.

[Chuck S.]

Duke Must Be Off This Weekend...

Jim, I concur with John on the "orange stuff". After installing Dexcool about two years ago, I am changing all my vehicles back to "green" as soon as it's warm enough to flush them good. It would be about time to change it anyway.

Want your hair curled?...Type "dexcool" into your browser window and see what comes up...mostly warranty and maintenance problems with factory-fill GM vehicles. The problems revolve around frequent coolant exposure to air, combined with frequent heating/cooling cycles.

A description often used is "brown gunk". I haven't seen that in my vehicles, but I have been plagued by coolant loss (no leaks, no indicated overheating) that leads to overtemperature problems with extended idling. That never happened until I changed to the Dexcool.

Dexcool is no longer cheaply available in this area; discount and auto parts stores no longer sell it. The only place I can find Dexcool to makeup for my loss is Texaco stations and convenience stores for $11-$20/gallon (OUCH!!!).

[Patrick H.]

Re: Duke Must Be Off This Weekend...

Chuck,

I've noticed that same unexplainable loss of coolant with DexCool since switching my truck over a few years ago. It's been only a gallon in almost 4 years, but still.... Unusually enough the previous owner put DexCool in my 72 coupe, and it's fine. Original rad, motor, etc. Maybe it will get switched back, though.

Patrick

[Duke W.]

I'm here!

I've been hanging out with the 12 year olds over at the Corvette Forum C6 discussion board trying to give them some education on automotive engineering and marketing, but it's an uphill battle.

I have noticed that Dexcool has more of a propensity to develop small leaks than green stuff - probably because the inorganic salts in green stuff tend to plug minor leaks when they precipitate out at the site of the leak.

I've had a pesky intermittent leak (very minor) on the Cosworth Vega that appears to be the coolant pump gasket, a couple of hose coupling leaks on the Merc, but none on the MR2.

I'm sticking with Dexcool because I still think it provides superior corrosion protection and will not clog up radiator tubes like the green stuff eventually does.

No problems with the "brown gunk", but then my cars get a coolant change every two years and don't go more than 6K miles between changes, so they don't get many cycles.

There have been problems with Dexcool, but consider that GM has built about 40 million cars since they started using it in '96 as I recall. Certainly only a fraction of one percent of those owners are experiencing problems and GM has laid some blame on owners themselves for running the cars for extended periods with insufficient coolant level.

The Zerex G-05 coolant used in all Daimler Chryler cars is worth considering as an alternative to Dexcool. It is a "hybrid" in that, like Dexcool, it has a organic inhibitor package, but, unlike Dexcool, a very small dose or inorganics, particularly silicates.

Duke

Duke

[Frank H.]

Re: 1971 454 thermostat question

I had a 70 that ran hot at times,turns out the radiator was 1/4 plugged in bottom tubes,and all the heater core tubes were reduced to a 1/3,The little old radiator shop nearby recored both my tank ends with new old dead stock units way below what replacements would have cost ,if I could have got them on a sat. and the car never acted up again.