New to classics.... The heater core in my Buick is leaking causing overheating of engine. Can I run a hose from outlet tube to inlet tube on waterpump, without running hoses to the heater core? Will this cause damage or more issues? Thx

Why are you saying your leaking core is causing overheating?
From your other posts, I assume you say it's overheating because you have steam from your defroster vents.
Steam coming from your vents means the heater core is leaking. That has nothing to do with overheating.
Unless you can provide other reasons. What else makes you believe you're overheating?

What happened to the prior posts to his question? I know I answered this, telling him to disconnect and block both hoses.

I'm with you, RocketDude. Sounds like he's seeing a mist and he thinks it's overheating.

Here's another brainstorm... If you know it's bad, replace the heater core! If you're not sure, bring it to a radiator shop.

Thanks guys...I'm not able to find another Heater Core anywhere. Thus, my dilema. It seems to only overheat when the steam starts coming out of the vents. Also, I have a new rad, t-stat, waterpump, hoses, and there is no blockage in the heads. I have also flushed engine 3 times and it does not seem to be blocked. Still, I only see an overheat when the core starts steaming or leaking. I don't have any other clues........ thx

Overheat..I have a new rad, t-stat, hoses, belts, wp. I have flushed engine 3 times and it does not seem to be blocked. I have checked heads. It only overheats when the def vents steam or heater core leaks. Temp goes to 280+ and boils over. No AC on. All belts are tight. I have seen newer cars overheat if the core is leaking, not sure if this applies to this car, though. Rad shop says rad is not blocked and I have done a pressure test on system, no leaks anywhere. No coolant in oil. Oil pump is accurately pumping. So, I'm wondering if anyone might have another idea......Thx

I had a bad core did not cause overheating. Is the cap on the radiator correct? And is the condensor in front of the radiator clean? For air flow. Is anything wrong with the fan, or could the wrong fan be on the car? Just a thought.

hmmm...I will check.. thx

Now we're getting somewhere..! Some information to go on. You did mention the parts you replaced, but not that the gauge reads hot ant it was boiling over.
Was all of the mentioned work done to resolve said heating problem, and it existed before the new parts parade?
Does the overheating occur both when driving and standing still? Have you had a radiator shop, or mechanic do a block test on it? You put a chemical into the cooling system and warm it up, then put a tool in the radiator and with draw some radiator fluid. If you have a cracked block or blown head gasket, the exhaust will turn the fluid blue, and you know if your have a problem in that area.
Always start with the basics. Too many novices tend to throw money at a problem, and end up buying many unnecessary parts.
Don't worry about the heater core until you fix the problem. Bypass it and forget it until later. If finding one is impossible, take the core to a shop and see about getting it repaired. That is not the best way, but it may be the only way, while you continue to shop for a new one.
I have some more ideas, but first I must quell the screaming coming from the next room. It seems I'm taking the wife shopping. Go get busy and feed us more info...!

I think that's where you were at when you asked about bypassing the heater.

Locate your heater valve. (The hoses go to it) and determine if it shuts off all the way, or if it diverts hot water back towards the radiator. If you aren't sure, you can test it by blowing through it. That will tell you whether to block the hoses or run them together. Simulate the valve closing off water to your core. Then, take the heater core out and have it replaced/serviced. Modine may make one to fit your application. (They seem to have one for every app.)
http://www3.modine.com/v2portal/page/por...content_012.htm
They're in Racine WI.

Harrison also makes cores for GM. If none of that works, you can always get a universal heater core. Measure the size of your OEM core. Good radiator shops have all the books that show crossreference, substitution, etc. Your '61 Buick isn't that hard to fix.

In the mean time, pressure check your system. Radiator caps maintain proper pressure to raise the boiling point. If you're in the mountains, and you don't have any pressure, your boiling point is below 200 degrees F (eggs won't get hot enough to hard-boil). Adding the proper cap will raise the boiling point to around 240, even though the thermostat opens at ~180. In short, you cannot run without a good radiator cap screwed down tight, and a system that holds pressure.

I assume you are driving normal speeds and you have reasonable air flow.

Well...I disconnected Heater Core, routed a hose from inlet to outlet on waterpump, flushed system again and put in new coolant. Also put on another Rad cap. Car now runs @ 210f at its' hottest. Evidently, the heater core leaking was the cause. Also, it was pretty nasty when I pulled it out, had major blockage. Thanks for all the advice...

Also could've been the radiator cap. That's one of the most common causes of overheating (and cheapest to repair)..aside from the thermostat.

The only thing a blockage in the heater core will cause is a problem with the blower blowing hot air.

On the other hand, if the heater core leak was bad enough, it could cause a problem with the cooling system holding preassure, and wanting to boil over at lower temps.

When the "overheating" happens, is the engine more prone to have "spark clatter" during acceleration periods? If so, does it sound like many cylinders doing it or just from one cylinder consistently?

Is the mechanical advance in the distributor free and working PLUS the vacuum advance operating as designed? A retarded spark situation can cause elevated coolant temperatures, sometimes.

With all of the parts which have been changed, there should be no significant overheat issues (even with a 195 degree thermostat). You can get one of the non-contact infrared thermometer "guns" (usually about $50.00 or so for the lower temp range versions) and check the thermostat openning and radiator temps to correlate them with what the gauge or light might indicate.

Was the radiator "completely new", rebuilt with a new core by a radiator shop, "rodded out", or "fixed" with some of the water passages closed off (where the leak might have been at an earlier time)? A cross-flow radiator can look fine at the top and be completely clogged up on the bottom . . . and you won't know it except with an overheat situation you chase and can't fix--been there, done that . . . where the heat gun thermometer can come in handy to check for "hot spots" or "cold spots" in the radiator core.

What about the condition of the fan clutch? Does it "kick out" and "kick in" as engine temps demand? This might sound a little flaky, but does the fan blow toward the engine with the engine running (as in bolted onto the fan clutch the right direction)? Presence and condition of the fan shrouds AND other air dams under the front of the car and baffles between the radiator and the front body structure?

Is the "overheat" at idle or driving down the road? How long does it take to happen? In what ambient temperatures?

What about the condition of the transmission? Is the trans fluid darker brown and smells "burnt" or fresher and still bright red?

I'm not sure where this deal is going to end up . . .

NTX5467