Cadillac inconsitant Heating problem ???

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PowerdogCadillac500
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Cadillac inconsitant Heating problem ???

Post by PowerdogCadillac500 » Sun Apr 04, 2010 2:11 pm

I have a Cadillac 500 engine.. ill go out riding and most the night the temp is 180. Then all the sudden the temp goes 210 to 220. :shock:
I would understand if i was running dry , but this is running in water. i can run dry most the night at 180 and then it will go to 220 on the water ???? :?: I have an expansion tank,and burp tank... Any ideas would be greatly appreciated... Thanks in advance Dan.....

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watersports7
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Re: Cadillac inconsitant Heating problem ???

Post by watersports7 » Sun Apr 04, 2010 2:23 pm

are you using a thermostat or restrictor plate
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Re: Cadillac inconsitant Heating problem ???

Post by PowerdogCadillac500 » Sun Apr 04, 2010 2:27 pm

i tried 160 thermastat and it did this... now I took out thermastat and doing same thing...

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Re: Cadillac inconsitant Heating problem ???

Post by watersports7 » Sun Apr 04, 2010 2:38 pm

for whatever its worth, the caddy seems to run a little warmer than other c/m engines on an airboat
IMHO ours ran around 180 normally and as high as 200 (never stayed there long though) you would see it rise then fall immediately
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Re: Cadillac inconsitant Heating problem ???

Post by PowerdogCadillac500 » Sun Apr 04, 2010 2:49 pm

right, Mine at 200 it starts bubbling in the burp tank.. i'm wondering if my cap is bad or just not enuff lbs.. cause it runs great sometime at 160 180 and then starts bubbling the expansion tank cap will even let steam out...... and burp tank bubbles hott.. gets real frustrating for sure........

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Re: Cadillac inconsitant Heating problem ???

Post by plumcrazy » Sun Apr 04, 2010 2:55 pm

a 71 cad 500 ran 210 in the car from the factory, the blocks have a high nickle content and really were designed to run a little warm , heat in a engine makes hp

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Re: Cadillac inconsitant Heating problem ???

Post by watersports7 » Sun Apr 04, 2010 3:02 pm

very true Plum, you could try a higher psi cap, for every 1 psi increase in cap pressure, boiling point is raised 3 degrees
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Re: Cadillac inconsitant Heating problem ???

Post by Deano » Sun Apr 04, 2010 8:58 pm

Dan,

If it's bubbling over into the burp tank at 200, it sounds to me like your cap is bad. How many pound cap is it? I had a similar scenario a while back and going from a 14 to 16 lb sovled the problem. That's running a gutted 160 thermostat and a drilled idle bypass plug.

You did plug and drill the idle bypass when you put in the 160 thermostat didn't you? If not, I'd suspect that as well as the cap.

Deano
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Re: Cadillac inconsitant Heating problem ???

Post by SwampMatt » Sun Apr 04, 2010 9:12 pm

Like Deano said, you can't take out a caddy thermostat without plugging the bypass hole directly under the thermostat.

And you can't run any normal GM thermostat in a caddy either. ALL caddy thermostats have a special shape so that when they open, they plug the bypass hole.

Use a freeze plug to plug the bypass hole. Drill a 1/8" hole before pounding it in. Then you can run a GM thermostat or a gutted one as a restrictor plate. But you can then NOT run the caddy thermostat any more.

I'm told that there are only two thermostats for the caddy (over the counter - not counting custom or special order) - they are a 180° and a 195° (i believe) I think 190° was stock in most of those motors. They are definitely meant to run warm. I've also heard it said that they are less fuel-efficient when run at lower temps. I never noticed it on mine. It sucks gas all day long. LOL

I'm surprised more people don't know about this. Even the airboat builders. Without naming names, the fella who built my caddy boat took the thermostat out himself. And it still ran hot. It was obvious that he (a reputable builder we all know) did not even know about this caddy quirk. I plugged the bypass hole myself after I learned it was there.

Good luck.

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Re: Cadillac inconsitant Heating problem ???

Post by PowerdogCadillac500 » Sun Apr 04, 2010 9:50 pm

i appreciate the help guys... ill change caps and get a restrictor and thermastat and give it a try.....Thanks Dan...

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Re: Cadillac inconsitant Heating problem ???

Post by Deano » Mon Apr 05, 2010 9:29 am

Dan,

Just to expand a little on what has already been said. If you didn't plug the bypass hole under the thermostat, that may be your problem, in that you may not be geting all the air out of the system, and it surely isn't flowing correctly when it is warmed up. The water coming out of the heads that should go past the thermostat to the radiator is getting back in the block. That would very likely explain it puking prematurely.

This is not a great picture, but the first one I found without digging.
(If this bypass talk has you non-caddy guys wondering, this should help.)
caddy bypass.jpg
caddy bypass.jpg (245.38 KiB) Viewed 1104 times
The standard Caddillac thermostat has an extension under it with a plug the same size as the bypass hole (shown here plugged). When the thermostat is shut the plug is up and this bypass is open and allows some coolant flow through the block. When the thermostat opens and the plug goes down, it shuts this bypass hole and routes all the coolant through the block in the normal fashion. The hole(s) that Moodfood eluded to that you need to drill is to let air bleed out of the block when it is cool and you are filling it. I drilled two small ones in this one, but plenty of folks use one. In either case I would put it (them) toward the front of the plug as that is where the air will accumulate when you first fill it.

With this plug in place, you can run any available Chevy thermostat you want (gutted or not). (FWIW, mine seems to run more consistent with a gutted thermostat as a restrictor, but a lot of guys claim no poblems with none at all.) If at another point in time you wanted to revert back to a Caddy thermostat, just remove this plug you'd be good to go. Could be that will fix your problem without replacing the cap.

Given the limited expense, and the potential for considerable grief, I would just replace them both if it were me. Hope that solves your problem.

Deano
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but it is not the path to knowledge; it has no place in the endeavor of science."
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Re: Cadillac inconsitant Heating problem ???

Post by PowerdogCadillac500 » Mon Apr 05, 2010 11:23 am

Dean-o thanks that makes it real easy to understand..i just got back from parts store...lol... i got the caddie thermastat and a 20 lb cap...
wish i would of seen this earlier....lol.. if i just put the caddie thermastat in. do i need to also drill a hole in thermastat plate to let air out?
or should i take thermastat back and do it the way shown in the pic? or will either work the same? thanks,

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Re: Cadillac inconsitant Heating problem ???

Post by Deano » Mon Apr 05, 2010 12:06 pm

The difference between running a Caddy thermostat or a different one is that the Caddy 'stats are only available in 180* and 195*. This means the engine will run hotter than if you use a lesser heat range.

While they do normally run around 200 - 220 in a land barge, they are not stressed, loaded and revved like in an airboat. The real drawback to that difference is like Maddog pointed out. You have a MUCH smaller window of time and temperature to catch something that may be or go wrong. In other words if you're normally running 170 and you see the gauage at 210, you know something is amiss and can check it out BEFORE you've down damage to the motor. If you're normally running at 210 and see the gauage in the same timeframe it's probably going to be closer to 250 and then you'er gonna be real close to the Oh Sh!t mode. Then, if it's not hurt, it will also take a LOT longer to cool down before you can even persue what the problem is.

Not that it can't be done. If you got a 180 and you can run with it around 195 or 200, that isn't really going to hurt it. (If you got the standard 195, I would reccommend that you regroup.) However, my luck doesn't seem to be like that, I prefer the cushion of "other than stock Caddy" setup in both time and temperature.

Again, I've had the best luck with a gutted thermostat and a stiffer cap. You're radiator may be up to a bigger task than mine though. If I were you I think I would try it first with the 160* stat, plugged bypass and the cap you have. Then if it still wants to get hot, you could gut the thermostat and try it again. If it still gets hot after that, you'll have to go back to the drawing board, but will have good information as to what is NOT the problem.

Deano

Oh . . . and yes, if the thermostat isn't gutted, I would put a couple weep holes in it perpendicular to the bridge holding the guts.
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but it is not the path to knowledge; it has no place in the endeavor of science."
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Re: Cadillac inconsitant Heating problem ???

Post by Ruagatr » Mon Apr 05, 2010 1:29 pm

Fyi...a John Deere thermostat has the proper blocking disc on the bottom AND can be purchased in a 160 .

Maddog

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Re: Cadillac inconsitant Heating problem ???

Post by crowhater » Mon Apr 05, 2010 1:58 pm

I have never had any of my Caddy motors spike up and down like that. 180 is the norm and they might get around 200 if I am running dry ground real hard. Caddy's like a little water temp before they start running good but they do not like high oil temps!!!! oil coolers are cheap and are a good insurance policy!
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Re: Cadillac inconsitant Heating problem ???

Post by Deano » Tue Apr 06, 2010 12:46 pm

Maddog, that's interesting. I knew about the oil filters but now that you say that, I think I may have been told about that before.
Must not have been from someone with your crediblilty though, or I would have remembered. I'm beyond that problem at least for now, but that's good information to have in any case.

Now for the million dollar question . . . What was the arragement that you ran in yours? The John Deere or other?
And what about you Bonds, Crow? I relayed my experience as I figured it would help Dan. I surely don't have any difinitive answers though. You guys have exercised these things enough that I figure that you probably do.

Deano
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
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