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Bubbles in radiator... :-(


CMil's Avatar
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04-07-04, 08:26 PM   #1  
Bubbles in radiator... :-(

After changing the oil, oil filter and fuel pump on my '86 Chevrolet 1/2-ton truck and performing a vacuum check, I shut the engine off and heard a hissing noise on the passenger side of the engine, lasting for maybe 10 seconds. As the engine had only run 3-4 minutes, the upper radiator hose was not even warm, but the upper heater hose was QUITE warm. Upon removing the radiator cap, I found a thin layer of small bubbles floating on top of the coolant. My guess is that the hissing and the bubbles are related. I'm thinking (in order of expense) head gasket, cylinder head, short block and long block. Any advice on how to pinpoint the problem? BTW, the engine is a 1970 350 block, one 1979 305 head and one 1981 305 head. I know, I know... but the truck came this way from the previous owner (those darn kids!) and I just recently started researching this monstrosity. Any help would be greatly appreciated. Thanks - Chris

 
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04-07-04, 10:09 PM   #2  
first do a block check on it either by taking it to a shop or buying a block check kit at your local parts store to see if you are for sure getting exhaust gases in the cooling system some bubbles are not always an indication of any major problems, as for your heater hose being warm, it should be cause it bypasses the thermostat and the upper hose does not and the thermostat would not of had time to open up in that short amount of time.
then once you know for sure you have head or head gasket problems then you can decide whether you want to repair that engine or just replace it and if you have no idea how many miles the engine has on it your probably better off replacing it.

 
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04-08-04, 07:47 AM   #3  
Thanks, bejay. You mention a "block check kit" - what should I expect to find in one? I'm going to check at my local AutoZone and NAPA stores to see if they have them, I just want to be sure I get the right stuff.

 
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04-08-04, 02:27 PM   #4  
A block test kit is a turkey baster type tool with a chamber inside. You but a small amount of Bromythol Blue (probably spelled wrong)inside. You put it to the top of the radiator with the engine running and draw some fumes into the chamber. If exhaust gases are present, the blue fluid will turn yellow indicating exhaust in the cooling system.
Have you even considered that noise being a vacuum leak from the booster, vacuum storage tank or the like?

 
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04-08-04, 02:50 PM   #5  
Thanks, Desi501. No, I hadn't considered a vacuum leak, but I suppose it's possible. The only vacuum-operated device on the passenger side of the engine conected right now is the vacuum advance mechanism on the distributor; I wouldn't have thought it could take as long to equalize as the noise was occurring. I do plan to check the distributor advance mechanisms to make sure they're working right, though.
The noise really sounds more like it's coming from the area of the head, but I will also look into the vacuum leak possibility. Thanks again - Chris

 
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04-08-04, 03:44 PM   #6  
If the truck has a/c and was on at the time(or defrost) you may have heard the static pressure equalizing in the a/c system.

 
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04-08-04, 03:49 PM   #7  
Originally posted by davo
If the truck has a/c and was on at the time(or defrost) you may have heard the static pressure equalizing in the a/c system.
Or a vacuum door releasing in the air box.

Thes bubbles you refer to, did you actually see bubbles form while it was running or maybe just some foam for another reason.

 
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04-08-04, 05:17 PM   #8  
Nope, no A/C. The only things connected to vacuum are the distributor advance, the transmission modulator and the brake booster. I didn't actually watch the bubbles form, either, so I could be jumping to conclusions thinking combustion leak into coolant. But the noise combined with the bubbles seems suspicious...

 
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