ES - 5th Gen (2007-2012) Discussion topics related to 2007+ ES350

Coolant leak at upper hose

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Old 08-10-21, 04:00 AM
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craig72
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Default Coolant leak at upper hose

Hey gang,
A couple weeks ago, I replaced the alternator on my '07. As part of that, I had disconnected the upper radiator hose to pull the radiator forward out of the way. When I buttoned everything back up, I was getting a drip from where the upper hose attaches to the radiator. This was occurring only when the car was warmed up and the system pressurized. The hose was old and I felt there was a small split where it fits over the radiator nipple, so I ordered and installed a new Gates upper hose. All seemed well, but it appears the damn thing is leaking again. I have not torn the engine covers off yet, but I can see it is still from where the hose meets the radiator.

Anyone have issues with the spring clamps going bad, or any other thoughts what might be going on? I'm so looking forward to tearing into this when I get home, seeing as how it's supposed to be 97 degrees with 8000% humidity today.
Thanks!
Old 08-10-21, 04:19 AM
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jagtoes
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If the hose is new and the wire clamp is not strong enough due to age try replacing the clamp first . You should also look at the neck of the fitting as you may have damaged it while taking off the old hose. Check where the neck fits into the radiator.
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Hayk (08-10-21)
Old 08-10-21, 04:33 AM
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Originally Posted by jagtoes
If the hose is new and the wire clamp is not strong enough due to age try replacing the clamp first . You should also look at the neck of the fitting as you may have damaged it while taking off the old hose. Check where the neck fits into the radiator.
This. It sounds like the radiator outlet has a fracture in it. You can rent a cooling system tester and pressurize it while it’s cold.
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Wilson2000 (08-13-21)
Old 08-10-21, 04:39 AM
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craig72
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Originally Posted by jagtoes
If the hose is new and the wire clamp is not strong enough due to age try replacing the clamp first . You should also look at the neck of the fitting as you may have damaged it while taking off the old hose. Check where the neck fits into the radiator.
I sure HOPE I didn't damage that thing. I'd hate to have to replace the radiator out of my own stupidity. The Gates hose pamplet DID say they recommend new clamps when replacing the hose, but I never listen.
Old 08-10-21, 05:33 AM
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craig72
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Originally Posted by Hayk
You can rent a cooling system tester and pressurize it while it’s cold.
Didn't realize there was such a thing. Thanks!
Old 08-11-21, 03:55 AM
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craig72
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Well, I picked up the Radiator Test Kit from O'Reilly on the way home yesterday, but it turns out I didn't need it. When I got home and while the engine was still hot, I removed the plastic engine bay covers and intake scoop and was able to get a good look at the upper hose connection. The leak is at the plastic seam of the neck. I know this was from me twisting to get the old hose off during the alternator repair. I didn't realize it was so fragile. I've taken a 5/8" section of the old hose and clamped it around this back part of the neck temporarily until I can get to it this weekend. Good times. Nothing like completing a repair, only to make another one for yourself


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99RX300PDX (08-13-21)
Old 08-11-21, 08:11 AM
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Originally Posted by craig72
Well, I picked up the Radiator Test Kit from O'Reilly on the way home yesterday, but it turns out I didn't need it. When I got home and while the engine was still hot, I removed the plastic engine bay covers and intake scoop and was able to get a good look at the upper hose connection. The leak is at the plastic seam of the neck. I know this was from me twisting to get the old hose off during the alternator repair. I didn't realize it was so fragile. I've taken a 5/8" section of the old hose and clamped it around this back part of the neck temporarily until I can get to it this weekend. Good times. Nothing like completing a repair, only to make another one for yourself

Thank you for sharing. It could be my mistake in the future. I will be more careful when removing the upper radiator hose to avoid this problem.
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craig72 (08-12-21)
Old 08-11-21, 09:33 AM
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LeX2K
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Hate to say it but the radiators Lexus uses in their recent cars suck, they just do. Cheap garbage, it's very disappointing. You didn't do anything wrong if you can't remove a hose without ruining the radiator then the rad is not worth a damn. Good news is the replacement Denso will fit exactly as original and might actually be better.
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Wilson2000 (08-13-21)
Old 08-12-21, 07:46 PM
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Hayk
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Originally Posted by LeX2K
Hate to say it but the radiators Lexus uses in their recent cars suck, they just do. Cheap garbage, it's very disappointing. You didn't do anything wrong if you can't remove a hose without ruining the radiator then the rad is not worth a damn. Good news is the replacement Denso will fit exactly as original and might actually be better.
I also found Denso radiators (1998 ES300) to have a flaw at the AT cooler connection. If you’re in an area where they salt the roads, I highly recommend to coat the steel cooler connections with POR15 or something similar before you install the radiator to prevent it from leaking in the future. I’ve had to replace two Denso radiators because of rust. Currently on my 3rd with POR15 applied.
Old 08-12-21, 08:11 PM
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LeX2K
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Originally Posted by Hayk
I also found Denso radiators (1998 ES300) to have a flaw at the AT cooler connection. If you’re in an area where they salt the roads, I highly recommend to coat the steel cooler connections with POR15 or something similar before you install the radiator to prevent it from leaking in the future. I’ve had to replace two Denso radiators because of rust. Currently on my 3rd with POR15 applied.
Those fittings do rust badly, the original rad has the problem as well but it takes way longer. I don't have good luck with POR-15 on new, clean metal though I prefer Rust Bullet.
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Hayk (08-12-21)
Old 08-13-21, 03:59 PM
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Wilson2000
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Before I begin any automotive maintenance or repair job, I take the Hippocratic Oath: FIRST, DO NO HARM!

A cracked plastic radiator bibb is a common rookie mistake even veterans make. Another rookie mistake is replacing the spring clamp with a worm-gear clamp. Because of its design, a worm-gear clamp can easily crack a plastic bibb. Something else to watch for is non-OEM hoses with different OD's than stock. If you change the OD, it can make the spring clamp too tight or too loose.

To avoid cracking a plastic radiator bibb, some will slit the hose, parallel to the bibb, so the hose can effectively be peeled back from the bibb. However, if one doesn't want to replace the hose, one may need to use hook tools to separate the rubber from the plastic, without stressing the bibb. Patience is key!
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