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How to fix a leak in the radiator hose


I have a 1995 Lexus ES300 in good condition, I discovered a leak in the connection from the upper hose to the radiator. Fluid is not spewing out, but I can smell it burning and there is some moistness after I have been driving. For now, I have just been filling up the reservoir every week until I can fix it.

I was hoping that the clamp is just loose. Should I buy a new clamp and tighten or just reapply the old one? The repair shop I took it in to recommended all new hoses, thermostat, fluid etc. but I don’t think that is necessary???

When mine started leaking there, it turned out the plastic radiator tank/fitting has a small crack caused by worn-out engine mounts. Hope that’s not your problem. You need to let the car cool (or do this in the morning), then thoroughly clean the area where the hose attaches, start the car up, let it warm up, and see if you can tell where the coolant is coming from. You could try replacing the clamp as a cheap fix, but it might not be the problem.

p.s. - you might want to find another mechanic, sounds like they just want to throw parts at it.

Your car is 15 years old! Change every hose and belt on it! Change all the fluids too!

I think that suggesting new hoses for a 15 year old car with one leak already is not “throwing parts at it.” (As long as you are replacing the hoses, you might as well change the thermostat. The OP doesn’t say, but they are probably way over due for a coolant change.)

Hoses may be needed, but I doubt that a bad hose is causing a leak at the joint. That’s what I mean by ‘throwing parts at it’. No evidence the shop did any actual diagnosis. If he has the problem my ES300 had (identical symptoms) he’ll pay that shop several hundred dollars and still have the leak.

You shelled out good money to get a reliable car that is trouble free. If you want to continue driving this car with the same attributes, have the hoses, thermostat, clamps, and belts replaced. It is quite possible that the leak is not in the upper hose to radiator joint but a crack in the radiator tank itself or the seal from the tank to the core. When the hoses get old and hard, they transfer more force and vibration to the attachment points likely causing the plastic tank to develop a crack or work the tank seal.

A new clamp is cheap and worth a try. It very well could be a crack in the plastic nipple the hose connects onto. If the hose(s) are old and questionable it would be a good idea to replace them.

If the upper hose has been taken off and reconnected a few times over the years it could be ready for replacing. If you overtighten the new clamp you might just crack the connector. If it wasn’t cracked before, it could crack from the extra torque if you overtighten it.

Obviously, I could just replace all the parts and hope that it works, but that doesn’t sound like a well thought out or cost effective solution. Thanks to those who actually try to solve the problem without just recommending I replace everything.

I think I’m going to try a new clamp, and while I’m installing the new clamp, I will clean the area and try to determine where the leak is coming from. I don’t think the hose itself is leaky, so the leak must be coming from this plastic joint fitting? How do I replace that or fix it?

If it’s not the hose, and not the clamp, then it’s probably a crack in the plastic fitting, which is part of the plastice radiator tank. If that’s the case you have to put in a new radiator, there’s no repairing it. As I said, mine resulted from worn motor mounts. I hadn’t noticed the resulting vibration (it must have worn out over time) but once I had the mounts replaced the car was quieter.

Good gravy, how much could a rad hose cost? $50?

Rubber deteriorates with age, regardless of miles, and a rad hose is a “single-point-failure” type of thing: if it quits working suddenly, you’re walking.

(Of course, you can “cheap out,” and try to get the old hose to re-seal. It’ll be difficult, due to the age (and loss of elasticity) of the part, and there’s an excellent chance you’ll have to re-do the repair in a year or two, when the hose fails entirely.)

As a cheap SOB, I know certain parts are good candidates for the “redneck repair,” to patch them up a bit and keep on drivin’. Rad hoses are a rather poor candidate.