zeeke

Issue with coolant coming out of the cap when I shut the car off. Running a 71 455 .30 over with a 70 W-455 aluminum intake and 70 Quadrajet, G heads, stock exhaust manifolds and dual exhaust. 180 thermostat and a wide 2 core aluminum radiator (the one Pep Boys was saying was copper last winter) with a 16lb cap. Points distributor advanced to 10 BTDC, AC Delco RS45 plugs gapped at .40. At best the car reaches 190* for a short time but runs consistently between 180 & 185 closer to 180. Every time the car is turned off fluid comes pouring out of the overflow tube. Haven't purchased a reservoir yet due to the extreme cost, but the time has come to take my lumps. I do have the heater core disconnected and the hose runs directly from the water pump to the back of the engine. The AC compressor belt is off as well. New fan clutch also installed. The car is a 71 Cutlass Convertible with a TH400 trans. rebuilt 2 years ago.

At present there is no trans temp gauge installed. Which leads me to another question: where does that get installed to?

Also anyone had any good or bad issues running a 160* stat? I've heard the oil needs the higher temperature to function correctly so I'm a little hesitant to go that route.

1970cs

Where do you have the fluid level at in the radiator when cold?
Have you pressure tested the cap?

Pat

RetroRanger

These cars run w the coolant~2" below the cap level w out an overflow. You can get an generic type overflow tank for $20 or a nicer looking polished cylinder type for $30. Or you can pony up an spend the bucks for a resto type type tank that does the same thing

oldcutlass

As the others mentioned, the level for your coolant should be about 2 or so inches below the water neck on the radiator. If you look on the firewall side of the radiator there should be a fill line. Sounds like you are in the never ending cycle of over filling after it pukes. There needs to be head space in the radiator to allow the water to expand, if there is none it will muscle paste the cap and onto the floor.

joe_padavano

Look for this mark on the radiator end tank.

Fun71

Yep, this is what I have on my car. Under 20 at the local parts store.

https://www.oreillyauto.com/detail/d.../54002/4528645

zeeke

The radiator doesn't have a noticeable mark on it but the 3 core I took out did so I just assumed to fill it to the ~2" level like the original.

Thanks for the tip on the res. I'll go for the aftermarket for the Cutlass but if I ever get the 442 back together I'll have to get the other one.

I'd have to assume even after it pukes it would be lower. This morning I checked it, it actually pushes pressure when I open the cap and it's about 1/2 way down. I haven't pressure tested the cap, but it was new. I know you can't go by that, but atmosphere being 14.7 PSI, yea I'm that kind of nerd, and it pushing slight pressure when I open it I'm betting the cap is good. I will test it when I get back home and let you know.

As for the coolant, I use a concentrate and do a real scientific way of measuring, dump the gallon in fill the empty with water, dump that in, then a 1/2 gallon of concentrate and another 1/2 of water. Is it possible to much coolant and not enough H2O or the other way around? Thanks again gents.

oldcutlass

Your scientific way is fine. The reason why you lose so much coolant is once the cap opens up it has to relieve the pressure until it can close again. It probably was not pressure you had when you opened the cap, it was vacuum. As water cools it contracts and forms a vacuum, similar to food jars.

zeeke

In VT now, Lake Bomoseen. I think I have about 1/3 of coolant and plenty of water. I'll put in what I have in the morning which should be close with a 1/3ed and a 1/3ed and look for an auto parts store.

Thanks again

I just thought of something else as I checked "What have you done to your Olds today". I changed the housing back to the original yesterday. The aftermarket one leaked at the goose neck connection as it's pressed into the housing. The coolant level was down about 2" (4" from the top) when I would check that and just thought it was the housing leaking. It did push from the cap but not nearly as much.

oldcutlass

See what happens on your next drive when you start with the proper level.

Fun71

Too much ethylene glycol can be an issue - the manufacturers recommend a maximum concentration of 70% for extremely cold climates, and more than this actually reduces the cooling abilities - but too little is not an issue for cooling, only for freezing. Straight water actually absorbs more heat than ethylene/glycol mixtures. I run about 33% as that gives me freeze protection down to zero degrees (0ºF), which NEVER happens in Arizona, and it absorbs more heat during the hot summer temps.

So I would say that you are good as-is and don't need to add more antifreeze to what you already have. Until winter, that is.

zeeke

Ok here's an update. Put about 1/2 gallon of straight water in the radiator, now guessing 2/3's water 1/3 glycol. Did some slow cruising this morning between 30 & 50 MPH. About 20 miles. Then got on VT 4 and did 70 for about 15 min. Never went above 160. Remember I'm running a 180 stat, so now wondering if the autometer gauge needs calibration. Temperature is about 68* fahrenheit here. Is it possible the water pump could move that much water through the bypass? When I stopped the car went to 170* with a slight drip. Usually goes up to 210*. When it cools I'll see if there is any change of volume for the coolant. When I get back home I'll see if there is an adjustment on the gauge and check it with a Fluke laser temp gun. It's the probe type with copper line into the back of the gauge.

After sitting in the shade for about 10 min. is't now at 195 which to me sould be completely normal.

oldcutlass

You should be running minimum temp of 180 with that stat. Are you sure its not a 160?

zeeke

Definitely a 180, that's why I'm now thinking the gauge is off. I'll know more when I can get a temp gun in it.

Fun71

There is no adjustment on the gauge. I would double check that reading with your temp gun, but I suspect the gauge is reading correctly.

zeeke

Drove home from the Adirondack park and puked a lot less with more water than glycol. Haven't had time to look it over yet, been on a 2 day grind since I got back.

oldcutlass

If the temps are in the proper range and its still puking, change the radiator cap.

zeeke

I know you guys like pictures. 1- existing cap cold, 2- Radiator cold, 3- existing cap after 5 min warm, 4- new cap after 5 min and 5- kit

Haven't gotten a chance to heat it up and test it with the temp gun yet. Left new cap on, but I'm ruling out the cap since they both read close to the same. The only stant cap they had was the flip type all the others were Car Quest. Maybe made by Stant maybe not.