Just back from my first car show outing with the winter project, a 45,000 mile barn find '72 Riviera Boattail (455 Code U). We replaced every component of the cooling system- recored the Harrison radiator (4 core copper), 160 degree thermo (I live in Palm Springs, CA), all new hoses, lower has spring in place, heater core and hoses, block pressure flushed, new vacuum advance and lines, new water pump and fan clutch. Timing and dwell were set to stock per manual. Drove just shy of 700 miles with no overheating and no signs of the engine being warm, but upon stopping the coolant temp rises and spits out the overflow if I run a/c at all. Running 40/60 coolant and water with Purple Ice. I'd like to cool her down enough to alleviate this condition- am considering adding electric cooling fan on the front or an even larger capacity radiator. My other 455's have not tended to warm- am I missing something? What do the experts suggest?
What's the pressure rating on the cap, and does the cap test OK at it's rated pressure? What's happening is that after shutdown the coolant in the block gets an extra dose of heat because there's no more circulation. All the cooling fans in the world won't stop that from happening. Devon
If the car has the stock distributor, it will be 1112110. The stock specifications for initial timing call for 4* BTDC. That is retarded timing, and just that alone will make the engine run hot at idle and low speed. If you do have that number distributor, be aware that it has a maximum of 18* of mechanical advance. That means your total advance (without vacuum advance), will be about 22*, about 10* too little to make maximum power. I recommend you power time the engine to get 32* total advance. If you want to do something simple to alleviate the hot running, just hook the vacuum advance to a manifold vacuum source. That alone will boost you idle timing 14-18*. That will make a big difference. With 18* of mechanical advance, you can easily run 12-14* initial advance and have 32* total advance.
Pressure cap is 16 pounds and also new. The vacuum advance is connected to a three pronged block on top of the intake manifold. Are you suggesting bypassing that and obtaining a different source?
Yes I am. That three prong thermo vacuum switch is part of the Transmission Controlled Spark advance. It's a pollution device that doesn't allow vacuum advance in 1st and 2nd gears. The take off for it is ported vacuum, so there is no vacuum advance at idle either. If you connect the vacuum advance directly to manifold vacuum, it will advance the timing via the vacuum advance. The engine will run much better at part throttle, and it will run cooler. You may need to lower the idle speed with it connected that way. Try it, it's easily reversible.
Yes, I myself try to remember all my querky questions when I anticipate seeing the Wizard in person! He is the man!
I got all kinds of "new" rad caps that don't hold pressure. Do you have an overflow bottle or just a hose leading to the bottom of the radiator? An over-full radiator with no bottle does exactly as you describe.
Yup, sounds very typical to me. Let it spit and don't top it off again. Doing so is just overfilling by definition on a system with no overflow bottle, and it's just going to do the same thing again and again. Unless there's been some temp gage monitoring that demonstrates an actual overheat condition, everybody's making mountains out of molehills here. Devon
A 1972 Buick should have an over flow container, along with the requisite 15 lb. cap. Still, checking the cap is good advice.
I agree with posts 9 and 10. No need for modifications. Your car should have an over flow catch on it. Let it do it's job. I'm pretty sure the people that designed these Buicks knew what they were doing. Bob H.
My car HAS its original overflow reservoir and a 16 pound pressure cap. Let me give you an example. I drove one segment on Sunday from Santa Barbara to Pomona, CA, non stop with the a/c on at about 70 mph. It's a little over 120 miles, and was the second segment of the day (Total run that day was 347.7) I popped the hood before I shut the car off, and the coolant was almost exactly between the ADD and FULL markings. Then once I shut it off, the level rose and overflowed to the point where the overflow reservoir was empty. I've had several big 455's and none of them have done this, so I'm not inclined to believe that it is normal.
Then some diagnostics are in order. (1) Have the new cap tested, it may be defective. (2) Check initial timing and for correct vacuum advance function, it's a good idea regardless of the symptom. (3) Put a real water temp gage on the car temporarily so you can get some numbers written down to correspond with the circumstances in which the problem occurs. Devon
Thanks, Devon- Your suggestions are most useful. I'm aware that new parts aren't necessarily good (I had to throw a brand new coil in the trash and make the drive on a 37 year old one) but I hadn't been suspicious of the cap. Timing and dwell were reset the day before the trip but can be easily rechecked. I'm thinking I need to hide a real temp gauge in the ashtray or somewhere just so I can see what is going on. I'm also going to try the suggestion on connecting the vacuum advance directly to the manifold. I appreciate everyone's assistance and will keep you posted. Jeff Stork www.reynoldsbuickracing.com
I like the hidden gage idea, but don't disable the stock warning light, you'll need that functional since you can't drive and watch the temp gage at the same time. With some brass fittings you can tee off the senders for the gage and light together if another coolant port on the intake manifold isn't available. If you hide the new gage, make sure you go with an electric version if it's going to move every time you open the ashtray...the capilarry tube on a mechanical gage won't tolerate repeated flexure. Keep us posted! Devon
What the actual coolant temperature? You really need to install a water temp gauge and even more importantly a oil pressure gauge while your at it. Much better than just guessing what the temp and oil pressure is at.
This is right from a 75 shop manual: BUICK COOLING SYSTEM DESIGN LEVELS: Road cooling--- 90 MPH with a outside temp of 125 degrees---no time limit city traffic----stop and go----outside temp 115 degrees---30 minutes MIN. Idle---70MPH to stop----outside temp 100 degrees----12 minutes in DRIVE 7.2% grade ----60 MPH--- outside temp up to 110 degrees--no time limit 7.2% grade----with 2000 lb trailer----50 MPH----outside temp up to 110 degrees----no time limit
