Not necessary at all. I didn't expect to hear that from the people at this forum....

 

I actually had a similar issue with a 400. It had the solid fan rather than a clutch version. I swaped the solid one on a 400with a clutch and it didn't make a difference. The test truck still warmed up. I eventually pulled the motor that didn't get warm for a rebuild. Its not finised yet but I have yet to solve the issue. I am interested in seeing what you find.

 

Alex, you're not out of line. I have searched for problems I have had with my truck and have found a lot of your threads to be helpful.

Same for you, montana, you've helped me a lot.

This forum is for helping, and just because someone posts a lot does not mean that they are trying to be annoying or trying to increase their post count.

Anyway, I have the same issue with my 400. In the winter, I notice if I let it idle before I get in it'll stay a little warmer. (Start it when I wake up, drive it away when I leave for school) then it'll almost run hot. Installing an aftermarket temp gauge is the best way to monitor this I believe. For example, I can fill my gas tank 4 gallons past full, and when I have a 1/4 tank left I have 3 gallons left in a 19 gallon tank. These gauges are more or less idiot lights.

When you drive, is most of it at highway speeds? It'll always run cooler highway than idling, because the air is flowing around the block and radiator way faster. 0mph w/ 800RPM of fan movement vs 65mph with 2500RPM of fan movement. I'm in the same boat as you and am watching eagerly to see what you find

 

Nah ya I totally get that it's always gunna run cooler on the hiway, but this has been weird. And well, I do do quite a bit of hiway driving, just being that I'm in New England, but at least half my miles are under 55. And beyond that, I don't want it to run at 145 on a mild summer night, hiway or not you know.

Good to hear I'm not the only one though......

I'm running an aftermarket gauge right now, but I will test it as I said.

But geez ya, I know I post alot, but I don't even look at my count?

And that's what I go for. I enjoy going deeeep deep into detail, one because I like to talk, but two, for just the reason you said, I hope the information in my posts that I had to work to find, will be more like a one stop shop for future readers. And I'm not out for blood with anybody..... I dunno, that caught me off guard.

Anyway though, very interesting input on these 400's, keep it coming if it's there..... I'll letchya know what I find.

AleX

 

My 400 also registers fairly cold even after driving it a lot, and it rarely if ever registers into the middle section of the temp gauge. This seems to be a common problem especially for 400 engines. I've wondered about it, but haven't done anything to address it yet. I'd rather have it run cold I suppose, than to have it run hot. At least my heater heats up quickly in cold weather, so that's fine with me.

 

I wasn't sure if I should revive an old thread for this or not, so I thought I'd just contact you directly., but your mail box is full .... so here we are

There is a good tech article by Marlin Davis in the back of the current Hod Rod Magazine about thermostats. Someone wrote in to HRM and asked just about the same question, but with a different engine (LS1 Chevy or something I think).

The gist of the tech blurb was that modern t-stats are dual rate units that do not "open/shut" at constant rates or temps. The older units are more desireable for situations such as yours.

anyway, just thought i'd pass it along. Should be the issue currently on newstands.

good luck

Mike.

 

Ya I hafta do something about that mailbox..... but thanks for passing it along anyway.

I'll have to take a look at that. If I get the very general idea of what you're saying though, you're saying that an older thermo (say 192*), wouldn't open at all until the temp was very close to 192*, and would be fully open very shortly after hitting that mark, but a newer one of the same temp rating might staaaart opening at 162* or something?

I wonder why it would be done that way. Guess I'll have to do that pot of water test and see what's really going on. Truck's been off the road for several days recently as I'm working on the steering, but I'll be able to test stuff more soon.

Thanks for the info! I'll pick up a copy, AleX

 

Hmm well I read the article. Nothing I hadn't really already thought of/had suggested to me.

I've had a couple Robert Shaw T-Stats in, and everything I've EVER heard says that that's as close to perfect as you can get for a Clevo.

I will check it on the stove, like I said, and I think I'll disconnect my heater and loop a hose, just for the heck of it, but beyond that I don't really know.

I'm trying to think if there's any way that stuff could be flowing the wrong direction. Maybe my water pump is bad, not turning, and the water's just kind of floating back and forth through the bottom hose, into the radiator? That just seems kind of stupid.

I guess I should see if covering my radiator helps at all, like the guy from the magazine did. You know though that makes me think. If that guy was able to change his temp by covering half the radiator, then that means his radiator is affecting his engine's temp, meaning his radiator is flowing, meaning his thermo is flowing. That means that his issue likely IS that he has a partial on/off thermo, but I don't know what that means for me, with 2 different Robert Shaws.......

Oh well, let's hit the stove!

 

So let me get this straight because I'm a little more than a little confused. Old thermostats opened at 192* only, not before then, and it was all open or no open? And new thermos are fully open at 192*, but they're starting to open before then too?

Looking forward to your results!

 

That seems to be what the article implies. Although I have no idea whether the new therms are fully open at their noted temp (192* in this case), or whether there may be an even bigger spread (say they begin to open at 152*, are halfway open at 192*, and fully open at 232*).

I could see why that would be beneficial. Far smaller temperature swings, much more constant temperatures, the metal parts of the engine expand the one amount, and hold there you know. Just an on/off works in theory, in a perfect world. But in reality, by the time the closed thermo has come into contact with 192* water/steam, the water at the beginning of the cooling loop is going to be even hotter. Then though, when the water goes through the radiator, it may hit the beginning of the cooling loop pretty cold, but the thermo will still stay open until that cooler water touches it. That's alot of swinging, all the time. Staggered opening allows the thermo not to overcompensate.

That's how I see it in my head at least. Someone correct me if I'm wrong.

 

I have been reading all of the post . I can't remember if you tried a mechanical guage or not with out reading them all again. If not, remove the sender for your original one and use that same area of the engine for the mechanical sender. Don't just try it in a different area on the engine. The original in my 79 shows about 2/3 of the way to the right side all the time ,but a mechanical one shows it working from about 170 to 192 ,up and down depending if i'm in city traffic or out of town. Original guages in these old trucks are just there to fill in the space, I'v owned four of them plus my bronco and none of them work the same if they work at all.

 

Nah I took the original sender out long ago. My gas gauge has always worked pretty well actually, but my voltmeter is permanently frozen right in the middle, my old oil pressure gauge was all over the place, and I don't even remember what the temp used to do.

I have new mech. temp, oil, and tach.

 

Well, we have data!

I tested my OLD Robert Shaw 333-192, the one that was in there when I first reported this issue, in a pot of water on the stove. I found the test almost impossible to perform as the water heated up (rolling boil, bubbles, and steam all obstructed the view), but once it was for sure open I turned off the burner, and the temp FELL at a perfect speed for observation.

I used a BRAND NEW, never installed, first time uncoiled mechanical supra(?) gauge, with the tip of the probe, and the thermo, both HANGING, NOT TOUCHING THE PAN BOTTOM, at the same level in the water.

The thermo began to close at right about 190* water temp, and was fully closed by just over 180* water temp. I believe the water cooled slightly faster than the metal of the thermo, and that that was responsible for the 3-5* "delay" in it's closing. The gauge or the thermo also could just be slightly off.

Regardless of that small discrepancy between what I saw, and what I assumed I would see though, I am very comfortable saying that THIS THERMOSTAT WORKS..... at least in the fact that it closes at the proper temp.

I also did a cold start test run on my truck today. I took advantage of the cool weather, let the truck cool off for like 2 days since I started it last, started it up today, and watched (and FELT) what happened. This test was done 100% NOT MOVING, in park. All seemed pretty normal as it warmed up, but upon hitting about 155* (on the installed mech gauge), the top of the radiator around the top inlet started getting very hot! I have a brand new Robert Shaw 333-192 in there!

By 165-170*, about an 8-10 inch wide area, right below the inlet, FROM TOP TO BOTTOM of the radiator, was very hot! The lower radiator hose was also very hot.

In this cool weather (though only about 63*, no breeze), it took twenty minutes to even break 190*, at which point I stopped the test, because the entire radiator was already fully hot anyway.

This all means one thing, the thermostat is LEAKING, and pretty badly. I *believe* badly enough to cause my underheating problem!

I have not cross checked the therms yet (new one on stove, old/stove one in truck), but I believe I will get very similar results.

Furthermore, after these two tests, I got an idea, and did the simplest experiment of all. I put the old thermo in my mouth, sealed around the outer rim, and guess what, I didn't die! AKA I COULD BREATHE THROUGH IT!!! It wasn't quite sustainable for breathing, about as well as you can breathe through a coffee stirrer, but I got several full in/outs before I had to stop. That is how much it leaked at human breathing pressure (maaaybe 1-2 psi??)! Imagine how much it must leak at engine steam pressure (up to 13 PSI on a standard radiator cap)!

This is not good!

 

Continuing in second post so people won't get scared way by length:

My next test will be to see just how much the thermo leaks before it even opens up. I will do one test on a cold start, one on a warm.

I will accomplish this by disconnecting the radiator hose at the radiator inlet (top), and simply letting it flow into a container, and replacing the lost coolant/water periodically until the thermo actually opens (at which point I will try not to get burned).

I know this will be disregarding the normal backpressure in the radiator inlet hose, radiator, and outlet hose, but that shouldn't be an issue anyway, because Robert Shaw thermostats are not supposed to LEAK based on pressure!!! That's one of their main selling points! No leakage, high flow water pump or not! And I'm running a stock pump! This test is just to get a baseline for just how much one of these can leak, on a cold start (when there shouldn't be backpressure anyway, except for the pump).

No matter what I find in this test though (I'm hoping for some juuuust stupid results), we now know that the radiator is a factor WELL WELLLLLL before the thermo's designed opening temp! That's not OK!!!

I'm sort of at a loss as to what to do here though.

FYI, to do the mouth test, you must put the cup (bottom) part in your mouth. This is the way that water actually flows first of all, but also, if you put the cup part outside it is very difficult to NOT have your lips seal around it too, and the water passes between the upper edge of the cup, and the bottom of the main ring/lip.

Anyway though, I don't build thermostats.... I'm not sure really what to do here. I could just go to the parts store and pick up a normal cheapie, but that won't seal that rear cylinder cooling port under the thermo, allowing the rear part of the block to heat up much slower, and possibly less, than the rest of the engine, which is just as big of an issue as the underheating. It's the whole reason you need a Robert Shaw type for a Cleveland.

In my mind, some rubber is required on the top edge of the cup to insure a real, total, positive seal, but I have no idea how I would do this, and what it might do to the other properties of the thermo. All that really comes to mind is installing different types of limiters past the thermostat, but that makes me imagine alllll sorts of weird overheating problems. There are reasons a thermostat was used in the first place, and not just static flow limiters.

Anybody else got any ideas???

I would encourage/even ask all those others who have posted similar problems here to do the very simple cold start, watch the gauge, and feel the radiator test, and see if your results are the same. AND REPORT THEM HERE PLEEEEASE! Whether or not they support what I've found!

What baffles me though, is how everyone with a Cleveland hasn't found this problem to be true. Maybe some R-S's seal better than others? Some engines surely run hotter and cooler than others. And some radiators are certainly more clogged than others, " " water pumps certainly flow more or less than others. Maybe all these factors combined, along with the choice in thermostat opening temps, the myriad of different radiators available in the aftermarket, and people's different climates have been enough to hide the problem of leaky thermostats?

I'm not sure, but there's something here. Let's get some more numbers YOU GUYS, and figure out what's going on!

Whew, back to real stuff, fingers are sore, AleX

 

What a difference a little (or actually alot) of antifreeze makes....... And now I see why.

I have recently been stepping up the amount of coolant in the radiator (the strength of the coolant/water mix). The stronger the mix has gotten, the more constant the temperature has stayed. The engine still heats way uppppp, but I still have no fan shroud. It was fairly warm out today (mid 70's), but I think this trend will continue. Driving around 25-40, the temp was just over 190. 40-55 or so, it was in the mid 180's, and didn't get lower than 180, even on a rainy day on the hiway.

My theory is that since the antifreeze raises the boiling point of the mixture, that there is less pressure in the system, the more coolant in the mixture, since less liquid will turn into gas (a process of massive expansion, think steam engine), and that the less pressure there is, the less force there is to force liquid and steam through the imperfections in the seal of the thermostat.

I can test this theory by measuring, on days of the same temperature, while parked, how quickly say, 1/2 of the radiator gets hot, with pure water, and pure coolant. This sill indicate volume of liquid passing through the therm before it should be.

Keep you guys posted, WAHOOOO!