Been trying to track down the exact location of a small but persistent coolant leak for a couple weeks now. Bringing it to the forum because it's leaking in such a unique location and wanted to see if others have experienced it before. It's a 2008 I5 with 154,000 miles and the radiator was replaced in July.

I've indicated the only locations that continue to collect coolant in the image below. Note: This is not my air intake box. This is just a picture I found that clearly showed the locations I needed to indicate.


Coolant collecting in the well where you bolt the box to the engine bay as well as right above the front retainer clip closest to the radiator.

There is minimal signs of coolant splatter around both of these locations on the air box but not significant enough to point to a source. The only thing that makes sense to me is a crack in the long hose that winds its way from the bottom of the coolant overflow reservoir and connects to the top of the radiator. So far, I have only inspected the hose while attached and I cannot pinpoint any holes or leaks. I've looked numerous times with the car running and at temperature, with the engine off, and when it's completely cool with no luck. I can get a picture of the current coolant situation if needed, but that front bolt well is basically filled up with standing coolant so we're talking about more than just a few drops.

Obviously I need to take the entire hose out and test it for leaks at this point but I have two questions that I wanted to ask here first before doing that.

1. Can anyone confirm the official hose size/diameter?? Everything I see says 3/8" ID heater hose like this one on RockAuto for the 2008 H3, but the current hose in my car is most definitely more narrow than 3/8". I tried sliding the new hose over the plastic fitting on top of the reservoir tank and the 3/8" hose is way too loose.
   
2. Once I get the right hose size, can someone educate me on how to go about replacing it correctly? I've been keeping the reservoir tank filled while dealing with the leak and once I go to replace the hose, I'm assuming some or all the coolant in the tank will drain out. Will I be okay to remove the hose, slide the new one on once it finishes draining out, and then fill the reservoir tank up again? Just don't want to get any air in the system by doing that so I figured I would check here to see if the recommendation is to go through a complete coolant replacement.

Appreciate any help or advice. It's just a strange location for coolant to pool up since nothing coolant-related is really over there by the air intake box other than the reservoir hose. No other signs of leakage on the skid plate, upper radiator hose, water pump, or radiator itself.

 

Simply pressure test the coolant system to find leak source!

Kits are cheap here:::::>>>>>

coolant pressure tester kit

coolant pressure tester kit

 

Uv rad dye. Simple black light. I've used for years.

 

Dye is great to detect seepage leaks. OP has a coolant spraying gusher leak under pressure.

 

I agree with Hummerz that you probably have a pressure leak. The hose going from the radiator to the tank should have little to no pressure. That hose on my 2010 is nowhere near the locations you show. And you are positive it is coolant?

If you do swap on that hose, you can probably unmount the tank and position as to minimize coolant at the hose port, then quickly swap hoses at the port after you route the new hose. You don't need to worry about introducing air - the little that is there will be cleared out in one drive cycle.

 

Quick update and follow up question....

I replaced both the upper radiator hose as well as the long hose from the radiator to the overflow tank. By the way, the correct size for the reservoir hose is 5/16" and not 3/8" like I was seeing everywhere else. 60 inches of 5/16" was the perfect length. Drained about a gallon before swapping the hoses, filled it up, and bled the system like usual without issues until I got out and drove it. I'm now leaking way more coolant that before but I believe I've tracked down the source to the water outlet housing behind the power steering pump. It was really difficult to see the bottom bolt at first, but 99.9% sure that's the issue. Must have been loosing a lot once the car got to temperature and it was spilling onto the belt which was then throwing it all over the air intake cleaner.

Has anyone successfully replaced the water outlet housing WITHOUT removing the power steering pump/bracket?? Looked up the water outlet removal procedure from Schwarttzy and it says to remove the P/S pump bracket (which also means take off the belt and remove the P/S pump). For the sake of time, I really don't want to do that and it seems like you can maybe fit a flexible extension with a 10mm socket and crack it loose without removing all that junk. Picking up a Dorman water outlet in just a bit and need to do this tonight.

 

Thanks for update.p

 

To answer my own question above, yes, you do have to remove the P/S pump bracket to gain access to the lower bolt on the water outlet housing. You'll need to remove the drive belt, air intake box, resonator box (or Air Doc intake, etc.), VVT solenoid, and disengage the clip that holds the wiring harness to the back of the P/S reservoir tank plate so it can move a bit more freely.

You can see in the Schwarttzy diagram from the hyperlink in my previous post, but there are four 15mm bolts holding the bracket to the cylinder head. You can reach three of the four with a regular ratchet and socket, but one bolt is too close to the P/S pump to get the socket on the bolt head. You can, however, fit a 15mm ratcheting wrench on it and loosen it that way. I would highly suggest a ratcheting wrench instead of a regular box wrench, though. It's very tight down there and I was only able to move the wrench up and down maybe 1-2 inches to loosen the bolt. Took a bit of work and my forearm was sore for a while after that, but it really wasn't too bad. Maybe there's a super skinny, flexible extension that could slide back there without removing the bracket but none that I have or have ever seen.

Also, I did not need to flush the entire system before swapping. I drained about a gallon from the lower hose when I swapped the upper radiator hose a few days back, but this time I just removed the water outlet and let the coolant drain out everywhere since I was planning to clean everything up anyway. Just be sure to fill the radiator and burp the system when you wrap up but so far so good for me. There's not a lot of write up on the water outlet and it was throwing me off trying to track down the source.

 

I was pretty sure you would have to remove the P/S pump bracket, but I also thought it might be done with just loosening the P/S bracket to allow a wee bit of movement if that were all that was needed and you could get away with it. I never replaced one on an I5, so I have learned something with this Thread.

Another successful wrenching episode by KU1525.

 

Interesting. Appreciate the follow-up.
The manual doesn't say anything about sealant or gasket for the housing. Is it just metal to metal?