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Car Forum / Honda Cars / October 200591 Civic cooling system pressure
My 91 Civic presurrizes the cooling system upon startup. The overflow tank is also under pressure and there is a slight leak under the cap. There was also a spare cap under the hood when I bought the thing not long ago. Is this pressure normal or is the head gasket going? There is no oil in coolant, no coolant in the oil, and it doesn't smoke. It runs good and doesn't overheat. But if you start it with the cap off it sprays coolant. Should the overflow tank be vented? I only see one hose. THanks in advance. On 10/19/05 6:24 AM, in article slrndlcato.6ma.chuck@localhost.localdomain, > My 91 Civic presurrizes the cooling system upon startup. The overflow > tank is also under pressure and there is a slight leak under the cap. [quoted text clipped - 4 lines] > sprays coolant. Should the overflow tank be vented? I only see one hose. > THanks in advance. Look carefully at the tank itself, there should be some sort of overflow tube built into it. I've never encountered a Honda with a pressurized overflow tank. My guess is that your radiator cap is bad and the overflow hole on the overflow bottle is plugged. > On 10/19/05 6:24 AM, in article slrndlcato.6ma.chuck@localhost.localdomain, > [quoted text clipped - 11 lines] > overflow tank. My guess is that your radiator cap is bad and the overflow > hole on the overflow bottle is plugged. I see no overflow tube. I pulled the tank off (it just slides into a groove built on the motor mount) and there's no vent tube. The cap to the overflow tank screws onto the tank and I can see no sign of tampering. I'll get a raditator cap and see what happens. BTW, the cap that's leaking is the radiator cap. Sorry I wasn't clear about that. > My 91 Civic presurrizes the cooling system upon startup. The overflow > tank is also under pressure and there is a slight leak under the cap. [quoted text clipped - 4 lines] > sprays coolant. Should the overflow tank be vented? I only see one hose. > THanks in advance. Something is seriously wrong here. Are you saying the expansion tank has a pressure cap on it? On your car there should be an 0.9-bar cap (13lb) on the radiator. This cap should allow pressure to bleed off into a tube in the rad filler nack that goes to a non-pressurized expansion tank. Is the rad cap aftermarket or OEM?  SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >> My 91 Civic presurrizes the cooling system upon startup. The overflow >> tank is also under pressure and there is a slight leak under the cap. [quoted text clipped - 7 lines] > Something is seriously wrong here. Are you saying the expansion tank has a > pressure cap on it? Well, it has a screw on type cap with the single hose from the radiator attached to it. > On your car there should be an 0.9-bar cap (13lb) on the radiator. This cap > should allow pressure to bleed off into a tube in the rad filler nack that > goes to a non-pressurized expansion tank. The cap is a 13 lb. I can't see how the expansion tank can be non-pressurized though. There's only the single hose going to it, and it screws onto the expansion tank unlike most snap on type ones that I'm accustomed to seeing. I see no apparent way for the tank to vent. The expansion tank is original...it slides right onto the motor mount bracket. Nevermind about the expansion tank...I found a hole drilled into a flat spot of the threads. > Is the rad cap aftermarket or OEM? It's an aftermarket. Does this *really* matter? I'm thinking about a thermostat, but it doesn't overheat and it does warm up as it should. What I'm thinking of doing is screwing my compression testing onto each cylinder and attaching to the air compressor and looking for bubbles in the coolant. I guess that would tell me if it is a head gasket. >>> My 91 Civic presurrizes the cooling system upon startup. The >>> overflow tank is also under pressure and there is a slight leak [quoted text clipped - 10 lines] > Well, it has a screw on type cap with the single hose from the > radiator attached to it. That's normal. >> On your car there should be an 0.9-bar cap (13lb) on the radiator. >> This cap should allow pressure to bleed off into a tube in the rad [quoted text clipped - 7 lines] > bracket. Nevermind about the expansion tank...I found a hole drilled > into a flat spot of the threads. The tank /has/ to vent. As your coolant heats up, it expands. As it expands it pushes into the reservoir, so the reservoir level will rise. When you shut down and the car cools off, the reservoir level will go back down again as coolant is sucked back into the rad. >> Is the rad cap aftermarket or OEM? > > It's an aftermarket. Does this *really* matter? Yes. If the cap is the wrong design for the car, or is defective, this will affect cooling system operation. Change it just in case. It's cheap enough. > I'm thinking about a > thermostat, but it doesn't overheat and it does warm up as it should. If it doesn't overheat, then the thermostat is fine. > What I'm thinking of doing is screwing my compression testing onto > each cylinder and attaching to the air compressor and looking for > bubbles in the coolant. I guess that would tell me if it is a head > gasket. Sure would. But if you're not losing coolant, then your head gasket is certainly fine. Other than your report of "spraying", it doesn't sound as if there's anything wrong with your car. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>>> My 91 Civic presurrizes the cooling system upon startup. The >>>> overflow tank is also under pressure and there is a slight leak [quoted text clipped - 54 lines] > Other than your report of "spraying", it doesn't sound as if there's > anything wrong with your car. I'm curious what effect a thermostat with the air bleed valve pointed downward would have on a system. This car also has hot/warm intermittant start issues and I'm wondering if these could be related to air (that I can't seem to get rid of) hitting the ECU temp semsor. It doesn't lose coolant and doesn't pressurize the expansion tank when running, but when cranking the engine and only when cranking the warm/hot engine, I hear air escaping from the vent hole in expansion tank. THe thing runs great except for the intermittant start issues. BTW, I've already resoldered the main relay and can hear the fuel pump at 'key on'. The next no start I guess I need to check for spark. I do get an Oxygen sensor code. From what I've read this wouldn't keep it from starting...would it? escaping from the vent in the |
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