I need some help with a cooling problem Oppo!

"matthewklein220" (matthewklein220) 10/29/2013 at 12:49 • Filed to: Advice, help

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My '69 Firebird is having a major cooling issue. Has been since the day I started driving it. It always overheats and empties the radiator into the overflow tank to the point where the overflow is overflowing. I've tried flushing the system, replaced the radiator cap, even replaced overflow and its hoses. Nothing so far has worked. I could really use some help, since I'm out of ideas aside from completely replacing the engine and cooling system.

HammerheadFistpunch > matthewklein220 10/29/2013 at 12:51

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I had a similar problem with my cruiser. Replaced my thermostat, and did all that you mentioned....had to replace the radiator. Works great now! sometimes, the coolant passages just get gummed up over time.

CalzoneGolem > matthewklein220 10/29/2013 at 12:52

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I'm concerned by the lack of mentioning thermostat changing.

AutoSavant > matthewklein220 10/29/2013 at 12:54

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Thermostat or radiator. Replacing the thermostat takes about 10 minutes. It's under the water neck.

matthewklein220 > AutoSavant 10/29/2013 at 13:03

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*slaps forehead* How did I not consider that?? Guess I need to make a stop on the way home.

matthewklein220 > HammerheadFistpunch 10/29/2013 at 13:05

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Well the engine had been sitting for years, and there was some serious rust in the coolant. When we flushed it it was the darkest shade of red-brown I'd ever seen and about the consistency of a milkshake. So it could very well be all gummed up.

HeelToe Do-See-Do > AutoSavant 10/29/2013 at 13:06

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I'll jump on the pile and say thermostat. They're cheap, and could probably stand to be replaced anyway.

Tekamul > matthewklein220 10/29/2013 at 13:06

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Have you noticed how long it takes to start filling the overflow? Any bubbles or funny colors?

If not, you're in luck and you probably need a thermostat. If you see bubbles or a darkening of the fluid, it may be a head gasket leak blowing exhaust into the coolant.

HammerheadFistpunch > matthewklein220 10/29/2013 at 13:07

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If the radiator is overflowing though, you know you are getting flow to and from your engine coolant passages, its likely that just your radiator is clogged.

matthewklein220 > HammerheadFistpunch 10/29/2013 at 13:08

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And probably the thermostat (like others mentioned), Which could be causing it to stick too.

matthewklein220 > Tekamul 10/29/2013 at 13:09

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Well it's still slightly rust colored, even after the flush, but there are a lot of bubbles...

Tekamul > matthewklein220 10/29/2013 at 13:12

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Bubbles -> head gasket.

At least that's my opinion based on my experience with blown head gaskets.

*edit* By all means, you should probably start with changing the thermostat, since that is a $10, 20 minutes task, and could be the issue. It's always good to start with the least expensive fixes when you're unsure.

matthewklein220 > Tekamul 10/29/2013 at 13:17

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Well a new engine is going in anyways, so a bad head gasket would just move up the date when I put it in the car. But I am going to try the thermostat first.

desertdog5051 > matthewklein220 10/29/2013 at 13:25

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First thing is compression check. If it is good or acceptable and none are way different then replace radiator.

mrazekan > matthewklein220 10/29/2013 at 13:28

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I don't know what they call it in English, but in Spanish it is called sondiar . Basically, the radiators caps are removed and the individual radiator tubes are power flushed. I don't care how many bottles of flush you use you will NEVER get it as clean as having a radiator shop pull the caps off and clean the inside of your radiator. They they solder the caps back on. It is easy with older radiators. Any decent radiator shop can do this but you must take the radiator out of the car for it to be worth the price.

Try this if the thermostat swap doesn't do it and you know you don't have a blown head gasket.

matthewklein220 > desertdog5051 10/29/2013 at 13:33

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I have done that. They're a bit high, but all withing a couple psi of each other.

matthewklein220 > mrazekan 10/29/2013 at 13:34

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That's a good idea. It's an older radiator, so they shouldn't have problems with that process.

mrazekan > matthewklein220 10/29/2013 at 13:42

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I mentioned it precisely because it is an old radiator. Easy to take the caps off and solder them back on. I did this to my radiator on my '79 F-250. I followed this with a continuous flush of my cooling system. I just left the tap on until the water came out clear. Then drained and refilled with mix and did not have a problem for the rest of the time I owned it.

desertdog5051 > matthewklein220 10/29/2013 at 13:42

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You might be able to get 69 radiator re-cored.

matthewklein220 > desertdog5051 10/29/2013 at 13:44

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It's not the original radiator.

MR2_FTW - Group J's resident Stig > matthewklein220 10/29/2013 at 13:49

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When my MR2 was constantly overflowing the reservoir, it was because the head gasket was slightly blown and would leak compression into the water jacket. Oddly this only happened under boost or at highway speeds, but that was definitely the cause. I drove on it like that for a year.

matthewklein220 > MR2_FTW - Group J's resident Stig 10/29/2013 at 13:53

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Would all the cylinders still give healthy readings on a compression test?

desertdog5051 > matthewklein220 10/29/2013 at 13:57

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New thermostat?

MR2_FTW - Group J's resident Stig > matthewklein220 10/29/2013 at 14:09

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Mine did. It could be a very slight slow leak like mine was. Perfectly fine around town, but blowing compression on the highway.

matthewklein220 > desertdog5051 10/29/2013 at 14:10

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Trying that first, then look into getting the radiator flushed if it doesn't work.

matthewklein220 > MR2_FTW - Group J's resident Stig 10/29/2013 at 14:11

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Ok, because I ran a compression test not too long ago, and all the cylinders were reading good.

Bandit > matthewklein220 10/29/2013 at 16:48

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I'm a bit late but I'd suggest changing the thermostat. It isn't too hard to do on a 400.

Frank Grimes > matthewklein220 10/29/2013 at 18:30

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make sue there is a good fan shroud.

matthewklein220 > Frank Grimes 10/29/2013 at 23:40

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Actually it runs electric fans which, after discussing the car's past with my dad, always seemed to give it trouble and may be compounding the problem.

matthewklein220 > Bandit 10/29/2013 at 23:42

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Well all the Pontiac blocks are the same aside from displacement, so it's literally the same as a 400. That's our first move. Second it a leak-down test to check for a bad head gasket, and then the radiator. And my dad and I have a hunch that the electric fans are making the problem even worse by not drawing as much air as we thought.

Frank Grimes > matthewklein220 10/30/2013 at 00:10

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How so? Not enough amperage?

matthewklein220 > Frank Grimes 10/30/2013 at 02:02

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No, just don't draw enough air. They're about 15 years old, and fan technology has come a long way. There are fans with double the cfm now.

Frank Grimes > matthewklein220 10/30/2013 at 13:24

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I heard taurus fans are a good cheap option.

matthewklein220 > Frank Grimes 11/01/2013 at 14:01

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Actually, this was just mentioned to me yesterday! And it's something I'll look into.