My 96 LSS does not seem to be transferring overflow coolant back into the radiator. What I have done so far is replaced the radiator cap (twice because I thought the first cap might have been defective) and had a mechanic pressure test the system with up to 15 lbs. of pressure. The pressure test revealed no loss in pressure so the cooling system seems to be intact.

A little history on the car. The radiator is a new one, replaced due to an accident. The car does not overheat at all and there are no problems with the engine that I can tell (no loss in power, no drop in gas mileage, no sign of coolant in the oil, no steam coming out of the tailpipe). It has 183,000 miles on it but runs like a champ.

The only problem I am having is that the coolant from the overflow tank will not return to the radiator. I have to top off the radiator once a week to make sure the engine has a sufficient amount of coolant. Has anyone out there experienced this problem? Let me know if I need to add more detail. Thanks in advance!

 

Check the hose in the over flow tank it should be touching the bottom or its missing. Coolant will fill the bottle but air will be sucked back in.

 

Checked the hose and it's all the way to the bottom. However, being that the car is 12 years old, I was wondering if I should install new hoses for the overflow system? There might be a crack or a hole somewhere in one of the hoses. Other than that, I am still stumped. Thanks for the reply!

 

Ya try a new hose from the top of the rad going to the overflow and from the overflow to the bottom of the overflow. It sounds like a bad cap but it new so. You probably have a 1.1 bar thy have 1.3 bar caps.

 

Got new hoses and installed them today. I "modified" the hose that sits inside the overflow reservoir. I attached that hose directly to the "straw" that goes through the reservoir cover. The factory set up has the hose attached to the reservoir cap and not directly to the straw. I can't really figure out why it was designed that way, it just seems weird to me. Also, the "straw" was very loose and I saw coolant bubbling out from where the "straw" attaches through the cover. I almost positive that is where the air leak is. I'll give it a few days and post an update to let you know if my "mod" fixed the problem. Thanks for your help!

 

Cool ya make it easy for all of us.

 

It's been a couple of days and the problem still persists; the coolant is not returning to the radiator. I did notice something and it finally dawned on me. Everytime I remove the radiator cap to fill it, pressure is being released. It's like opening a soda can. Even when the engine is cold! I believe since there is never negative pressure in the radiator, the coolant from the overflow reservoir will never get sucked back in.

So now I am wondering if there is a problem with the head gasket allowing pressurized gas to get into the radiator. Like I said in my previous post, there are no obvious problems with the car. There is no oil in the radiator, no coolant in the oil, no steam coming out of the tailpipe, no loss in power or gas mileage. One thing I do notice is, the engine seems to misfire when starting up cold. I rap the throttle a couple of times and that clears it.

Should I open another thread on this topic to get responses from others? Thanks!

 

Keeping this same thread is fine. Even before I read your latest post I was going to suggest that your engine may be pressurizing your coolant. You can do a compression or leakdown test to find out if you have a headgasket leak. Or, if you have an air compressor, you could rig up a boost leak tester and see if you bubble your coolant with it.

 

My mechanic pressure tested the cooling system with up to 15 lbs. of pressure. He said it held the pressure but I am not sure how long he tested it. I'll see if I can get him to do a compression test. Could a leak flow one way (into the radiator), and not the other (into the cylinder)? I would think so because of the higher pressures of the combustion process versus the lower pressure of the cooling system. And once I "depressurize" the engine when I turn it off, the coolant may be seeping into the cylinders causing the cold start misfires. I am just speculating at this point but I guess the logical next step would be a compression test. Much obliged for the advice!

 

??? There are 2 different types of caps honda uses are you using the rite one ???. If it was a bad head gasket the pressure test would reveal a leak and you would probably be smoking.

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See how thy look different on the ears (not just the ears the hole cap is different). Is your cap hard to get off?