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| TimoG | Coolant boiling/gargling sound when the engine is turned off | ||
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Guru Newb
 
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I've recently had the intake manifold gasket (and intake manifold as it was corroded) replaced by a local mechanic. The parts including the manifold were all OEM. Since the repair, I've had to top up the radiator several times within probably about 400 miles of driving. Usually what would happen is that the "low coolant" light comes on and when I check the level in the radiator once the engine has cooled down, the level in the radiator is between a 1/4" to 1" below the filler/pressure cap neck on the radiator. I followed the instructions in the owners manual - start the engine with the cap open, top up until the coolant level reaches the bottom of the filler neck, then put the cap back on. Header tank is filled to the "hot" mark at this point. Driving the car at this point shows normal engine temperatures (185-200 degrees, I rarely see the temperature hit even 210 in the mountains). After letting the engine cool down over night, I noticed that the level in the header tank only changed minimally, if at all. this behaviour was present before the repair, too - the level in the header tank pretty much never changed. Last night when I checked the level in the header tank with the engine hot, I noticed that there was a sound of gargling/boiling coolant from the front of the engine, somewhere below the throttle body. Given the engine temperature (coolant was around 200F when I turned off the engine), I was a little surprised by this, is that normal for a C4? The only other car/truck we've owned with a similar engine (a slightly newer GMC truck) certainly didn't do that, but that one also ran at an indicated 210F once the engine was warmed up. Apart from the new manifold and gaskets, the thermostat and the radiator cap were both replaced with OEM-spec parts (ie, no low temperature thermostats or high pressure caps). I guess the main question is - is this normal behaviour, or do I need to take the car back into the shop? I normally do most of the work on our cars myself and at this moment I'm kicking myself that I didn't do this job myself, too. |
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Posted on: 2012/10/6 16:58
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| BillH | Re: Coolant boiling/gargling sound when the engine is turned off | ||
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The Stig Moderator
 
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It can gurgle when parked hot BUT this is usually coolant going from the header tank back to the reservoir.
Gurgling under the T/B sounds like there's air in the system. It helps to jack up the car or park on an incline to put the radiator higher than the engine but - with the cap off and the engine warmed up enough that the thermostat is open, with the car running, open the throttle to 1500 or so and fill the header tank up to the cap, then put the cap on wothout releasing the throttle. Release the throttle after the cap is on. This helps push the air out. Ypu can also drill a 1/8th hole in the thermostat which will help purge the air. All this will work IF the mechanic did the gasket correctly. Ypu should probably have the system pressure tested, possibily Autozone or whatever would do that. I don't have a pressure tester buy feel free to stop by if you get up this way. Are you going to be at the racetrack next weekend? |
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Posted on: 2012/10/6 17:45
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| Matatk | Re: Coolant boiling/gargling sound when the engine is turned off | ||
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Webmaster
 
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What Bill said. You need to "burp" the system. You can easily do this by yourself. Start the car and remove the radiator cap. Use the throttle body linkage to rev the motor to 1500-2000 rpms. I just do it until the coolant starts dropping in the radiator, then fill as much as I can and put the cap back on. Usually once will do it, you might need to drive it and let it cool off then do it one more time to get everything.
I don't really do this while the car is too warm. Something about opening a hot radiator cap doesn't appeal to me. Good luck, Matthew |
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Posted on: 2012/10/6 17:54
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| TimoG | Re: Coolant boiling/gargling sound when the engine is turned off | ||
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Guru Newb
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Quote:
That's my impression as well. It doesn't *quite* sound like it's boiling, but it could well be air bubbles moving around. Quote:
The mechanic already offered to do a pressure test, plus I have a trip to Harbor Freight come up. I might just get a pressure tester... Thanks for the offer, once I have a better idea what's going on I might want to consult you for a second opinion. Quote:
Unfortunately I'm still hobbling about on an injured foot - it's getting better but I don't think it's not a good idea to drive a car with a manual transmission, especially on the track. Quote:
I've attempted burping the system the way you described it three times now, albeit not with the front of the car elevated. I'll probably give it one more shot with the front of the car on ramps to see if it makes a difference. Quote:
For some reason, it doesn't appeal too much to me either  . |
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Posted on: 2012/10/6 18:11
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| Matatk | Re: Coolant boiling/gargling sound when the engine is turned off | ||
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Webmaster
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I jack up just the passenger side of the car, it helps.
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Posted on: 2012/10/6 19:34
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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