I've been watching the temp gauge on my '55 Bel Air lately, and although its not problematic I'm curious. When sitting in traffic it'll heat up to 215 or so, but cools right down to 190 when I begin moving forward. Mechanical fan, no clutch, no shroud, and 190 thermostat on a mild 350. Granted, its 110 here all summer so you come to expect a warm running car. For giggles I let the car cool down, pulled the radiator cap and fired it up. It sat for a good 15 minutes idling at 190, never hotter. I don't remember ever seeing a 16 pound radiator cap before (really high PSI in my mind), I was thinking 8-10 would be more appropriate. What do you guys recommend? Sent from my DROID device using the TJJ mobile app
16 pound is standard on late model vehicles and has been for some years. Your Chev was probably about 7 pound when new. Your radiator and engine may be OK with 16 pounds pressure, if you have a new rad and good rad hoses. But what about your heater? Other than that, you car seems to be running perfectly and the cooling system is doing its job. It won't go under 190 once warmed up because you have a 190 thermostat. 215 is not that much higher especially on such a hot day. You can go to 240 with a 16 pound cap before you even start losing coolant.
Thanks Rusty, the rad is in good shape, hoses are new, heater is not connected. Sounds like I might be worrying about nothing.
Yep a 16 lb cap won't help the engine run cooler as it actually allows it to run hotter without boiling over. I'd have to believe that up to 215 in slow traffic and dropping right back down to 190 with a 190 thermostat is called NORMAL without a thing wrong with it. More fan might keep it a bit cooler but I don't think you have a thing wrong except maybe a bit more cap pressure than an older radiator could handle. If it is a new replacement radiator there is nothing to worry about.
all the 16 pound cap does is raise the boiling point of the water. I have a buddy who's car would over heat in the texas weather. one day he switched to an 8 pound cap from the 16 pounder and has never looked back. he swears it made it run 20 degrees cooler.
16 lb will blow a hole in the heater core and dump boiling coolant on your better half's feet. If its only overheating in traffic I think you probabaly need to hook up your vacuum advance to manifold vacuum so you aren't running retarded timing at idle. That's what Chevy did.
I don't believe a stock 55 radiator will live long with a 16 pound cap. My 56 split open like dropped watermelon with a 14.
You can also buy 180 degree T'stats... I'd also hook up a clutch fan... So what if it ain't traditional... Who cares! Those things do work!..
I picked up and car (gasser) from a buddy and on it's first drive, it got up to 215 and wouldn't come down no matter how fast I went. It was an aluminum radiator with a 20 lb. cap. It had a flex fan, no shroud with a big moon tank in front. I checked the thermostat and found none. Also the vacuum advance wasn't hooked up. I put in a 180 thermostat and hooked up the vacuum advance. She ran at 180 after that and I kept the 20 lb. cal.
I wonder if he topped off the radiator a gallon or two while he was at it... I don't have the heater plumbed in right now, hasn't been since we picked it up seven or eight years ago. For all I know the heater core is bad, but good thinking! HEI distributor too but thanks for the ideas, I'll file them away and use them on countless other projects. Kinda what I was afraid of. I'm sure it's been recored, but the top and bottom tanks look like nice originals. I just may do that, thanks. Could do the 180 thing for sure, but wanted to address the problem itself. And I have no issue with a fan clutch, the sucker has HEI for hell's sake! And two tenths in the quarter! Thanks. Sounds like it couldn't have had a worse airflow situation! So often there are simple fixes to problems that elude others for years, which is exactly why I asked the question!
So I've got a question. My 50 dodge with a 360, brand new mustang v8 radiator runs at 190 while going down the road but stopped and idling it goes up to 235. I'm running a stock thermostat for a 79 cordoba, a clutch less flex fan, no shroud, and whatever cap came with the radiator. I guess I should keep in mind it's been about 105-110 degrees lately... Never spews coolant but 235 seems pretty high to me....
The boil point of a 50/50 water / antifreeze mix is raised 3 degrees, for each 1lb of pressure. Doing the math,.. 16 lb raises the boiling point 48 degrees. Add that to 212, and the "new" boiling point is 260 degrees. 215 degrees in that situation is well within the range of acceptable. It would be well worth the money to have the radiator and heater core checked out by a good radiator shop. Happy Roddin' 4TTRUK
Why run a 190 degree thermostat? I would go with a 160 degree thermostat and a stock 7-8 lb radiator cap. If this does not work have the radiator cleaned and check the water pump for corroded fins. It is stupid to run 190 degree thermostat and then wonder why the engine coolant temperature is high. Do not buy a new aluminum radiator. Copper radiators have a "R" value that is half of aluminum. You seem to be going in the wrong direction.
I'm no expert (obviously) but I've always understood that 160 isn't even operating temperature. I'm not wondering why the car runs at 190 when I have a 190 thermostat.
Just had the top radiator tank split on my 59 chevy...took the radiator to a radiator shop to have it repaired, and he said that my 13lb. cap was way to much, then he asked me if my heater core leaked...sure enough 6 months earlier it started leaking...so he repaired both and then told me to run a 7lb cap.
I was always taught in the pre-smog 60s that 180 was the proper temp for a thermostat. I never heard of a 195 thermo until the federal emissions requirements went up. The higher temp was for emissions. If you are running a vacuum advance dist., make sure that it is hooked up to the manifold vacuum source so the timing is advanced when idling in traffic. If it is hooked to the modern emissions ported vacuum source then the engine will tend to over heat when idling in traffic due to the retarded timing. This is often misunderstood so I bring it up. Just something to check before you start to throw money at it. I've never had a problem with overheating on any of my cars that could not be fixed without heroic feats and money. I fought one high temp problem once only to find out that it was actually running normally at 180. I had the wrong sender for the gauge. A 55 Chevy with a SBC never needed any shrouds in the 60s.
Make sure the fan blades are in the right direction. I fixed a jeep the other day that had the fan blades installed backwards.
Not to hijack, as they say... While I think I understand the relationship between the system pressure and the boiling point of the coolant, the blown / EFI'd 2000 GM 3800 V-6 in my truck runs a steady 207 most of the time, which is pretty normal these days for smog motors, as I understand it. But I'd be interested in using a slightly lower pressure cap if I could to get the overall engine temps down to, say, 195 so that operating temp would be much closer to the rating on the thermostat. A worthy goal, too? Or another problem? What are the common pressure ranges of radiator caps? Gary
Reread what was said above...the rating of a pressure cap will have NO affect on the operating temp at all. It merely affects the temp at which the coolant in your system will boil over. If your car never gets above 200 degrees, there is no reason to have a high pressure rating. It's not a status symbol. I've never had a pressure cap above 8Lbs for any hotrod. My late model shit runs a higher pressure cap for emission purposes and I use what the manufacturer recommends.
Excellent reply. When these new cars run above 200 degrees, they get really hot when the engine is shut off. There is no coolant circulation and the coolant meets the temperature of the engine block. This is hot and the coolant will boil just sitting in the driveway. The high pressure caps keeps the coolant from boiling and covering the driveway. An old SBC, flathead and SBF are not designed to run at high temperatures and high pressures of the modern day engines. The thermostats do not always open and close as marked. The Ford Barners always recommend placing a thermostat in a pan on the stove with the wife's candy thermometer and see what temperature the thermostat actually opens. Some temperature gauges and thermostats are probably off by (+/-) 10%
REALLY glad I found this thread! I have a 16 lbs cap on my recored '54 radiator that I wanted to replace for cosmetic reasons, and then I read about the heater blowing the hell up and it all makes sense! My heater was leaking, so we bypassed it. Not sure if the core is shot, but I plan on fixing it and getting a lower pressure cap! Thanks!
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