Mysterious coolant consumption/loss
#1
Mysterious coolant consumption/loss
My 72 350 is losing coolant somehow. It was so low after a two hour drive today that the heater stopped working. When I opened the radiator cap, there was no water in sight. The inlet radiator hose was almost empty.
There's no sign of leak from the heater, or from any of the hoses/couplings. The spark plugs are all nice and tan.
My question: can the plugs be tan if I'm burning coolant?
There's no sign of leak from the heater, or from any of the hoses/couplings. The spark plugs are all nice and tan.
My question: can the plugs be tan if I'm burning coolant?
#3
It's amazing how quickly the coolant level can drop with even a very small leak. It only leaks when under pressure, which means while you're driving, making it hard to see. And then since it's so hot, it evaporates quickly instead of leaving puddles.
Get the engine good and hot (highway driving), then stop in a safe and quiet area and shut down the engine. The cooling system pressure will rise even higher, as the heads put their heat into the system but the radiator can't dissipate it, since neither air nor coolant is flowing.
Use your senses (sight, sound, and smell) to find the leak. Common areas are the weep hole on the snout of the water pump (typically indicating its bearing is almost gone) and all around the intake manifold (a mirror and bright light helps to see the back). But of course it could be the radiator, heater core, heater control valve, or a hose as well. And, of course, check your crankcase to make sure the oil's not getting milky, indicating an internal leak.
Get the engine good and hot (highway driving), then stop in a safe and quiet area and shut down the engine. The cooling system pressure will rise even higher, as the heads put their heat into the system but the radiator can't dissipate it, since neither air nor coolant is flowing.
Use your senses (sight, sound, and smell) to find the leak. Common areas are the weep hole on the snout of the water pump (typically indicating its bearing is almost gone) and all around the intake manifold (a mirror and bright light helps to see the back). But of course it could be the radiator, heater core, heater control valve, or a hose as well. And, of course, check your crankcase to make sure the oil's not getting milky, indicating an internal leak.
#4
My 72 350 is losing coolant somehow. It was so low after a two hour drive today that the heater stopped working. When I opened the radiator cap, there was no water in sight. The inlet radiator hose was almost empty.
There's no sign of leak from the heater, or from any of the hoses/couplings. The spark plugs are all nice and tan.
My question: can the plugs be tan if I'm burning coolant?
There's no sign of leak from the heater, or from any of the hoses/couplings. The spark plugs are all nice and tan.
My question: can the plugs be tan if I'm burning coolant?
At that time, my "coolant" was plain water since it was a new build and I didn't want to waste antifreeze if there was an issue. The plain water didn't make white smoke out the exhaust like antifreeze does, so it wasn't initially obvious that the head gasket was leaking.
#5
Well, I'm getting a form of whitish smoke, but it's also freezing over here, so I had put that down to being normal.
The pressure test will definitively tell me whether it's a coolant leak or not? I can do one easily. Second will be to get it hot, shut it off and listen/look/smell for a leak.
Would it make sense to torque down all my head bolts for good measure?
Will the milky oil be visible on the dipstick?
The pressure test will definitively tell me whether it's a coolant leak or not? I can do one easily. Second will be to get it hot, shut it off and listen/look/smell for a leak.
Would it make sense to torque down all my head bolts for good measure?
Will the milky oil be visible on the dipstick?
#6
Oil will only be visible on the dipstick if coolant is leaking into the oil.
There's no harm in retorquing the head bolts. They're not those fussy European torque-to-yield types.
I would do the pressure test both hot and cold - expansion of the metal can seal a very small leak when the engine warms up.
You should hear a leak even if you don't see one, but (I've never tried this...) you should be able to hear a head gasket leak into a cylinder by removing the spark plug and listening through a tube placed in the spark plug hole.
The cooling system should hold pressure for a good long time, theoretically for over an hour, so if it loses pressure while you watch, you know there's a leak somewhere.
- Eric
There's no harm in retorquing the head bolts. They're not those fussy European torque-to-yield types.
I would do the pressure test both hot and cold - expansion of the metal can seal a very small leak when the engine warms up.
You should hear a leak even if you don't see one, but (I've never tried this...) you should be able to hear a head gasket leak into a cylinder by removing the spark plug and listening through a tube placed in the spark plug hole.
The cooling system should hold pressure for a good long time, theoretically for over an hour, so if it loses pressure while you watch, you know there's a leak somewhere.
- Eric
#10
#15
You mean it goes from the "FULL" mark to the "ADD" mark on the dipstick, right?
If so, then that means you're using about a quart every 1,500 miles, which is perfectly reasonable, especially for a used engine.
As for the overflow - once it's out that hose and on the road - it ain't comin' back.
- Eric
If so, then that means you're using about a quart every 1,500 miles, which is perfectly reasonable, especially for a used engine.
As for the overflow - once it's out that hose and on the road - it ain't comin' back.
- Eric
#16
Yes, exactly. The engine has done at least 100k miles, (the odometer is at 63k km, and I suspect it's done at least 160k, if not 260k).
I meant if I installed an overflow bottle - I'm WELL aware that it doesn't magically whisk back up the hose once I park if there isn't a bottle.
I meant if I installed an overflow bottle - I'm WELL aware that it doesn't magically whisk back up the hose once I park if there isn't a bottle.
![Big Grin](https://classicoldsmobile.com/forums/images/smilies/biggrin.gif)
#17
Yeah, a quart every 1,500 miles is great for an engine with over 100k.
I had a Buick with a 350 and 135k once that used a quart every time I filled the gas tank.
As for the coolant... Now I understand.
If you get an overflow bottle (a soda bottle with a hose in the top will work fine), and you have a "Vacuum / Pressure" radiator cap, AND there are no signifcant leaks in the system,it will suck the fluid back in when it cools.
- Eric
I had a Buick with a 350 and 135k once that used a quart every time I filled the gas tank.
As for the coolant... Now I understand.
If you get an overflow bottle (a soda bottle with a hose in the top will work fine), and you have a "Vacuum / Pressure" radiator cap, AND there are no signifcant leaks in the system,it will suck the fluid back in when it cools.
- Eric
#18
Yeah, I rigged an overflow bottle, and switched to a rad cap that had "return overflow" or something similar on it. We'll see what happens with THAT.
Compression test read 100-130 PSI, those two being the extremes.
Compression test read 100-130 PSI, those two being the extremes.
#21
head gasket
I would suggest removing all the plugs and pressurize the cooling system over night try to keep 15 psi on the system and in the morning are after a few hours have some one spin the eng. over while some watches at the spark plug openings to see if coolant comes out the plug holes, make sure u stand aside and not directly in front of the plug hole. as an auto tech we cked. head gasket leaks all the time this way and it would tell on what cyl. the leak was
thanks ray
thanks ray
#22
Im with MD sounds like head gasket or head, if there is a crack in the head on the exhaust side it will just pump it out into the exhaust on the compression stroke and bypass the plugs altogether.
If the heater was leaking, inside the car would be muggy and the windows foggy but check the hoses anyway.
If the cars an auto check the trans isn't fuller than usual.
But a pressure test will confirm.
Scott
If the heater was leaking, inside the car would be muggy and the windows foggy but check the hoses anyway.
If the cars an auto check the trans isn't fuller than usual.
But a pressure test will confirm.
Scott
#24
Gotcha on all counts. I'll do what I can before I button her up again this weekend.
EDIT: The radiator caps in question:
hlrazMd.jpg
EDIT: The radiator caps in question:
hlrazMd.jpg
Last edited by Seff; February 2nd, 2014 at 04:26 AM.
#25
http://www.ebay.com/itm/VINTAGE-AC-R...194993&vxp=mtr
Any auto service shop should be able to test a cap for free probably.
Any auto service shop should be able to test a cap for free probably.
#26
Registered User
Join Date: Apr 2013
Location: Bonaire, Dutch Caribbean, Ft. Lauderdale Fl.
Posts: 141
Can't tell you, how many bad caps I serviced when looking for coolant leaks, it's the first place to look, also sometimes the rad. neck, inside where the cap is supposed to seal. Pressure test everything before you take anything apart.
#27
Seff, it's pretty busy at work today, so I can't get too deeply initi this, but the RC-15 that you had on your car originally is, according to my limited research, a pressure-only cap, while the other one looks like a pressure-vacuum cap.
The pressure-only cap let's pressure out, but not back in, while the pressure-vacuum cap allows the radiator to suck the coolant back in from the bottle.
Check the bottoms of the caps - the P-V cap will have an extra central flapper button that can move downward, allowing it to suck fluid in.
- Eric
The pressure-only cap let's pressure out, but not back in, while the pressure-vacuum cap allows the radiator to suck the coolant back in from the bottle.
Check the bottoms of the caps - the P-V cap will have an extra central flapper button that can move downward, allowing it to suck fluid in.
- Eric
#29
If you want the coolant to return to the radiator from your new overflow resevoir, there's two other things you should do in addition to using the proper type of suction cap:
1/ Make sure the hose extends all the way to the bottom of your overflow resevoir. Otherwise you'll be suckin' air.
2/ Fill the radiator all the way to the top, and even fill your resevoir about 1/3 full. That way, if you ever see the resevoir is empty, you'll know the radiator has sucked extra coolant back in, meaning you really are losing it somewhere. Your system will constantly be pushing coolant into the resevoir and sucking it back in. That's normal.
In contrast, with the older style, one-way caps, you never want to fill the radiator all the way. You need to leave air space so the coolant can expand without overflowing.
1/ Make sure the hose extends all the way to the bottom of your overflow resevoir. Otherwise you'll be suckin' air.
2/ Fill the radiator all the way to the top, and even fill your resevoir about 1/3 full. That way, if you ever see the resevoir is empty, you'll know the radiator has sucked extra coolant back in, meaning you really are losing it somewhere. Your system will constantly be pushing coolant into the resevoir and sucking it back in. That's normal.
In contrast, with the older style, one-way caps, you never want to fill the radiator all the way. You need to leave air space so the coolant can expand without overflowing.
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September 10th, 2013 06:48 AM