Upper heater hose keeps popping off

2001 LEXUS LS 430

140,000 MILES • V8 • 2WD • AUTOMATIC

JONSOLOW13

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133 POSTS
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Two days ago, the upper heater hose popped off and we stopped the car before the engine locked up. I went out and bought a standard piece of hose (checked diameter) and put it on with clamps. It was very difficult to get on one end because there was no ridge on the part the hose fits onto (see photo).

Within 30 minutes of driving the same thing happened. Could it be the thermostat locking up? Never had this happened before. Also, we checked after putting on the new hose and saw when the thermostat opened (car was idling as we checked it).

Any ideas would be super helpful.

Apr 22, 2022 at 8:28 AM

SQM

CERTIFIED EXPERT
6,383 POSTS

Hello,

Are you experiencing overheating?
If you have a stuck closed thermostat, it will cause the engine to overheat. With overheating there will be higher pressure inside the cooling system and that can cause the hose to pop off.

Also keep in mind that unless you use the specific molded hose that is made for the specific application, it can also pop off, due to the universal hose is not designed to take the specific pressure and can have more stress on the clamp.

I did not see a picture. Please try to upload it again.

https://www.2carpros.com/articles/replace-radiator-hoses

Let me know of any questions.
Thank you.

Image (Click to enlarge)

Apr 22, 2022 at 2:48 PM

JONSOLOW13

MEMBER
133 POSTS

Thanks for your response. Here is an update:
It's not the thermostat. The darn heater diverter valve assembly upper hose end broke off with the old hose which was why there was no ridge. We bypassed the valve assembly, and everything is fine. Just no hot air on demand but it's getting hot in FL. so it doesn't matter (LOL).

I'm ordering another valve assembly unit.

Jon

Apr 23, 2022 at 10:59 AM

SQM

CERTIFIED EXPERT
6,383 POSTS

Glad you got it figured out.

Thank you for using 2CarPros!

Apr 23, 2022 at 1:53 PM