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very slow coolant leak -- hose parts?

569 Views 12 Replies 7 Participants Last post by  dmf415
2007 Sienna LE with ~200k miles. I noticed that my coolant was low in the overflow tank. It was a good bit below the "low" mark but I could still see that there was some coolant in the tank. There was no overheating issue. I was just doing fluid level checks.

I had to replace the water pump in March. I assume the coolant was filled to the appropriate level at that time. The next time I did any maintenance was in September when I got the oil changed. Not entirely sure if they checked fluid levels or just did the oil change. So this is either a 9 month leak or a 3 month leak.

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Red line is about the level where the coolant was.

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The hose and clamp right below the radiator cap seems to have a leak at the connection point. Green box is zoomed in below.

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I think the spots in the yellow box are coolant leaking from below the radiator cap that dripped down onto the pipe and burnt off. I am not 100% sure if the red box is accumulated drippage from above or a leak itself at that connection point.

I don't have good access to the lower pipe/hose but I cleaned off the hose below the radiator cap. This is one week after cleaning it.

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Definitely seems like a leak there. Not only where the hose connects but around the clamp as well.

I left a mark on the coolant overflow tank after I refilled it last week. It has barely moved, if at all, in one week. There are no drip spots under the car either. This is a very slow leak.

What all is involved in replacing the upper hose and the lower hose? Does anyone have part numbers? Any other spot I should check for leaks?

Thanks.
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I recently saw a video of car care nut doing a water pump replacement on a Lexus LS460, he broke a similar hose off the radiator in similar fashion. I think he said that Lexus actually made the new radiators outlet larger for that hose and sold a replacement hose with a bigger diameter to Prevent future failures. Otherwise you’ll be replacing the Radiator with the same size outlets if there is not an improved design.
 

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Discussion Starter · #6 ·
I couldn't tell exactly which one that is but ended up being part number 902-408.

Less than a cup spilled in this process and it seems like the coolant level has not changed in the reservoir. I haven't topped up any yet. Does anyone know if I need to bleed the coolant after this replacement or is it not needed for this?
 

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I couldn't tell exactly which one that is but ended up being part number 902-408.

Less than a cup spilled in this process and it seems like the coolant level has not changed in the reservoir. I haven't topped up any yet. Does anyone know if I need to bleed the coolant after this replacement or is it not needed for this?
So have you already replaced the radiator? Here's what I do after cooling system repairs-IF the car has a air bleeder fitting, use it. This is usually a 10mm threaded & tapered fitting near a high point of the system. Regardless, I slowly fill the radiator and look for leaks. Once that's full, fill the reservoir to a few inches below the very top; never mind the fill marks. Start the car and let it run at idle for 20 minutes or so while checking for leaks and monitor the temp gauge.
If no leaks or other issues, go drive it for another 20 minutes and shut it off and let it sit a few hours to completely cool. Now fill the reservoir to the high mark. It's safe to open the reservoir while hot; BUT DON'T TOUCH THE RADIATOR CAP!
And I will continue to verify the reservoir level and look for leaks and check the temp gauge for a week or so. The system will draw as much coolant as it needs from the reservoir and settle out after a cool down.
 

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I couldn't tell exactly which one that is but ended up being part number 902-408.

Less than a cup spilled in this process and it seems like the coolant level has not changed in the reservoir. I haven't topped up any yet. Does anyone know if I need to bleed the coolant after this replacement or is it not needed for this?
The radiator cap is keeping the coolant in the radiator! Until you run the engine and the coolant gets hot, the coolant would stay put!
However, when you replace that part, you will need to drain some, but probably not enough to require bleeding the cooling system; just drain enough to replace that part!
 

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Discussion Starter · #9 ·
I only replaced the radiator cap filler neck, which is the plastic part. Specifically I got the Dorman 902-408 part from O'Reilly's. In the process I had to pull two hoses off and that drained some coolant, but not much at all like a few spoonfuls. The radiator cap also had to come off to move over to the new filler neck. I did not replace the entire radiator.
 

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I couldn't tell exactly which one that is but ended up being part number 902-408.

Less than a cup spilled in this process and it seems like the coolant level has not changed in the reservoir. I haven't topped up any yet. Does anyone know if I need to bleed the coolant after this replacement or is it not needed for this?
Yes bleed to air out.
Second see if you can find out were the leak is coming from.
If it is around the radiator, or reservoir could be a bad cap.
Most like a good burp will do.
 
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