Hey guys. Trying to fix my overheating problem in my Cadillac. (1950 with stock 331) I ran some prestone cooling system flush, which I know is weak, but I figured why not. The radiator has been acid bathed and flow tested. New water pump. Here is the interesting thing. I ran it for a while without the thermostat. What I noticed on my temperature gauge which has 3 tick marks (right most being hottest) is that while driving down the road or up hills the gauge ran up to the 3rd right most tick mark indicating running hot. When stopped at a red light the gauge would eventually lower back down to the center. I figured that the coolant must be flowing too quickly for the radiator to cool it off so yesterday I re-installed the thermostat, new coolant and distilled water, and burped the system. Well sure enough once the engine warmed up that temp gauge went all the way right again. To double check myself against the old temp gauge I ran the car with the cap off and a metal meat thermometer from the grocery store. Once the car warmed up it pretty much hung out around 205-207. Still sounds hot to me. My next plan is to knock out some of the freeze plugs in the block so I can try and hose it out. I hope to God its not a cracked head, block, or head gasket. My questions are - how bad is that running temp of 205ish, am I going about this the right way? Any suggestions, words of wisdom, or good lucks would be greatly appreciated!
well.....331s and 365s are known for cracked heads. Do the hand test. Place your hand in the center of the radiator. If its cold its plugging up. It should be hot all over. Radiators tend to start plugging in the center and works its way out toward the edges. I know you said it was cleaned and flow tested.....but if there is crap in the block then its now in your radiator.
That sounds like a fairly normal borderline temp to me, but check to make sure your fan belt is tight if its getting hotter under acceleration as the belt could possibly be slipping a little if it didnt get tightened good during the water pump change. Were you having problems before the work was done?
Well I just got the car about 5 months ago. I installed a new pump myself because the old one went bad the second we ran it to pull off the tow truck. Ive changed the coolant about 3 times roughly since then, and hosed it out a good bit, but never pulled the freeze plugs yet. From my understanding a car of this vintage can build up some hefty rust and scale down there. I pulled the generator pretty tight when I put a new belt on so I dont believe thats the case. Rad feels quite hot throughout. I'll check it again though.
Does it have a fan shroud? Have you checked the timing and if the advance is working correctly? Is the exhaust system partially plugged?
No fan shroud. I have not checked the timing but it runs smooth, revs up smooth, idles well etc. exhaust is pretty much rotted away before the muffler.
Shroud.. those cars ran as cool as can be with no shroud from the factory. 205 is not really that hot. With the t-stat open, how is the water flow in the radiator? It should be moving pretty well. Go with the advice in post #2, even though the radiator has been cleaned, it is still 64 years old. I would go with popping the freeze plugs next.
Flow seems fine, I dont really see too much movement. Not sure how obvious it should be. My shop manual says to test flow I could race the engine up with the rad cap off and it should flow over the top if it was restricted. I did that and it seemed fine, no over flow.
My shop manual doesnt clearly indicate what the standard operating temp should be. It says it starts to reach normal operating temperature around 170. Also it says high temp thermostats should be fully open at 185 to 190. I think 205 is still too high. Whoever owned this car before me had no thermostat in it either. Something is wrong here. I hope its just s build up of junk somewhere.
Look for a post on here regarding running vinegar through the cooling system. It seems to have had good results in a lot of cases.
I drained everything. Partially was able to get a freeze plug punctured but not out yet. Theyre not like usual plugs, theyre really solid and inverted. Now, when looking down the rods of the radiator closely with a flashlight, of the few that i could see, two looked partially clogged and one looked fully. I removed the rad and plan to take it back to the shop where it was cleaned and flow tested on monday. I really hope this is the issue.
Ok. Got all the freeze plugs out today. Quite dirty behind them. Looked like black/brown mud. Scratched it out with a hanger and then removed the thermostat/rad/heater hoses and hosed everything out really well. Theres still a little bit of greasy mud at the bottom. Im going to put in 6 rubber expanding freeze plugs and fill it up with some degreaser, let set for a couple days, and pull some plugs and reflush it out.
Heating up on the road or hills, cooling down at stop lights sounds like an air or water flow problem. I don't think some scum in the bottom of the water jacket is your problem
Well, that scenario was while the thermostat was removed. I was thinking the water was circulating faster than the radiator had time to cool. However, it seems to have some partially clogged rods so it needs to be rodded out.
205-ish is not overheating!!!! it won't even make steam at that that temp in a non pressurized system You worry too much. Does it call for a pressurized cap and if so is it relatively new? You would be flabbergasted at the actual cooling system temps in a modern pressurized cooling system. If it is not boiling over and making steam you don't have a problem.
I remember my 56 buick wagon would heat up fast too while testing the used motor and trans I put in it. I look down the radiator like you did with a flash light and saw it was clogged .I tried everything people said to try on here but nothing worked.I found a small radiator shop in town and the guy rodded it out for $50. and then no over heating. Best $50 I ever spent. Bruce.
What a deal! The shop that acid washed and flow tested mine wants 150-175 and thats per side or something? The lady said crud from the engine likely reclogged it, which I could understand, BUT there was part of a rusted spring sitting on top from the old rad hose. I think they didnt look too closely, especially because I took the new rad hoses I bought from them (which are springless) and put them in when installing the freshly cleaned radiator. So who knows. They have a good reputation in town.
It was steaming some. And that 205 was just from sitting and idling for about 10 minutes or so. I think the thermo I have in it is 185? The temp gauge in the car was pegged too.
Like Bruce said, at the very LEAST have the radiator rodded out. The shop will pull both tanks off the core and run a rod through each tube. The ONLY way you will know for sure. Best is to install a new core. Part of owning an old car. Ben
Thanks. I was made very aware of that potential problem by an older mechanic friend. The rad shop I bought the hoses from said the hoses for my caddy didnt comr with springs anymore because the rubber was stronger nowadays. They checked their catalogue in front of me and called their supplier. Those hoses werent cheap either. I think I paid $40 for 2 and they were cut to fit types made by gates.
check the timing too. cads have a reputation of overheating if the timing is off even a little. I drove my avatar for YEARS with the same symptoms you listed above--running temp 205 ish and after running it crept up to as high as 220. I just recently retarded the timing some and dropped the running temp by 15-20 degrees on average. should have done that long ago!
no need to rent really. that's why it took me so long--I don't have a light. f it's running fairly well it's close it's just a matter of tweaking and you can do some of that by feel/sound. loosen the distributor retainer while it's running and turn counter clockwise (if you were looking at it from the driver's seat) until it just about stalls out then go forward enough to smooth it back out. I had problems with dieseling when it was hot--retarding the time took care of that too--that's really the main reason I finally bit the bullet and adjusted it. I'd juste resolved myself it being a hotter than I'd have liked.
Yeah my fiance's step dad who was a mechanic for many years and knows old cars adjusted it by ear for me doing just that. I think likely the radiator needs to be rodded out.
Once you have the radiator reinstalled please put some form of filter in the top hose to stop any more crud or rust going into the radiator. I 've mentioned this before on HAMB - I put a new radiator in a car and didn't think any more about it till the car over heated - the new radiator was as blocked as the old one because the crud in the engine kept circulating. Even a bit of the ladies pantyhose slipped over the top inlet pipe of the radiator with the radiator hose slipped over the top will catch the debris - check it after a few runs and you will be surprised at what it stops/collects. With any old engine like this the amount of scale or crud in the internal passages will be considerable and with you now running the engine this scale/crud needs to go some where. As firstinsteele said - it's part of owning an old car. Once you have cleared this she will run and be cool for a long time - don't forget some anti freeze while you are at it even if it doesn't freeze your way
Update. I installed all new freeze plugs, 2 gallons of apple cider vinegar and topped the rest off with water. No thermostat. It ran much cooler for a while. Took over a half hour for the temp gauge to go over the middle which was great. However after around that time I revved it up and the temp gauge got up high again. I can see rust bits floating through the water. It would go up and down with occasional bubbles when it started to get hot. Ive made progress compared to before, and Im hoping the rad is just not flowing well enough. Otherwise it would seem like a cracked head or head gasket.
A cracked head or blown head gasket would show different symptoms to what you have described. My bet is your radiator cooling fins are blocked from all that rust and the engine cannot cool once it gets moving. A cracked head or blown head gasket could pressurise the system and blow all the water out - or suck the water out via the crack and then over heat but that's not what you are describing. My money is still on a blocked radiator
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