I’m stumped...Can anyone give me a hand on this one?

At startup after engine rebuild a coolant leak emerged at the lower radiator hose connection to the Water Pump housing neck. I can’t get rid of it. Didn’t leak before rebuild.

What I’ve done:
- replaced the new hose with another new hose
- replaced the worm gear clamp with a constant tension Mishimoto clamp
- cleaned the water pump housing neck with emery cloth
- inspected the water pump housing neck for damage and adequate ‘barb’ at end. It’s as good as any Ive ever seen on any engine
- applied Permatex ‘The Right Stuff’ liberally to the neck (last ditch effort) and reinstalled the hose and tightened.

STILL LEAKING!!

what am I missing? This is my first 13B rebuild, so is there some trick here I’m dumb to?
Thanks in advance for your help.
Rick

 

Are you using OEM rubber hoses? I’ve seen silicone hoses weep under load.
Replace or inspect the heater hose to the firewall pipe, that could be your culprit.
Turbo hoses and/or sensors in that area are prone to leaking.
Did you replace the water pump?

There is no trick to fixing leaks in that area that I’m aware of except “all new OEM hoses” or “switch to electric pump”.
I’ve never used RTV/Permatex to seal a hose, that might make your problem worse.

 

Thank you for getting back to me.

I am using brand new silicone hose. I can see the leak; it is between the housing neck and the lower hose. I can see the coolant seep out the top of that hose. It’s not the heater hose or the water pump; it’s at the joint I’ve described.

I understand what you mean about the sealant at the joint, however I’ve used it before in similar situations and it’s worked. And it does leak less with the sealant in this case.

i will use your suggestion about the OEM hose.

Why is it leaking now and didn’t before the rebuild? With the same new hose? And a new replacement?

Thank you again.

 

Faulty aftermarket products (x2)

I never understood any use for silicone radiator hoses, OEM or bust.

 

*Are you confident the ID of the silicone radiator hose is the same as OEM rubber? Personally not much of a fan of the silicone hoses either. OEM always fits, is relatively inexpensive and lasts along time.
*Casting crack on the neck during R & R or storage during rebuild?

 

OEM hose to be here tomorrow am. No surprise it’s not in stock at ANY Mazda dealership in the DFW Metroplex.

I’ll check the ID of the OE hose and compare to the Pettit Racing and HPS hoses, neither of which have sealed at the housing neck. I’ll report back.

i inspected the housing neck for cracks (did I drop the housing during R&R?) the third time I had this joint apart. Nothing VISIBLE...could be hairline not visible to a 63 year old eye. I think I’m gonna remove the housing for closer inspection; CRAP!

thank you all for your input.

oh, silicone has longer service life and holds up SIGNIFICANTLY better in high under hood heat temps. This is a track car and I wanted the extra protection.

 

Aftermarket coolant hoses are going to be hit and miss. It's possible there's a pinhole leak in the hose itself or something. Regardless I think you're on the right track putting an OEM hose on.

The OEM hoses are fantastic - they last a VERY long time. They can easily take the heat.

Dale

 

Thanks for weighing in All!
My bad for dismissing (not trusting) the Mazda mothership on the hose. I’ll loop back on results.

-Rick

 

What can happen on a defective hose is an interior pinhole leak that lets coolant get to the reinforcing cords. The pinhole leak can be anywhere along the entire length of the hose. Once it gets to the cords, it runs along the cord(s) and out the end of the hose.

Similar things happen with air springs or tires, except there, it's the pressurized air that leaks out.

 

Ok Folks—the bad news is the leak persists with the OE hose and a constant tension hose clamp (Mishimoto).

looking at the car cabin (Facing the windshield) the seepage is at 11 o’clock on the water pump inlet neck topside. Sleeping out from between the neck and the hose.

Im flummoxed, or worse. HaHaHa.

i guess next step is to remove the WP housing and get a good hard look at the neck and anticipate a hairline fracture in the neck.

any other thoughts?

 

Hey Rick...If you need I have an almost new neck (950 miles).
Jim T

 

Hello Jim
The location of the leak is the lower rad hose to WP housing neck...the part you reference here as available is the upper rad hose ‘neck’.

i wish it were the part you have...hours easier than the lower unit.

regards-Rick

 

Odd question....but did you try cleaning the surface with alcohol or some sort of degreaser? If you have oil on the surface of the hose or the outlet neck it's likely to seep a bit.

The other question would be are you sure the leak is coming from the hose? Any chance it's coming from the pump itself and just settling in the overlap material of the hose?

 

Wasn't sure were your leak was...glad I posted pic.
I have a WP housing but not new like the fill neck.
Let me know if you need it....no charge.
Jim T

 

Appreciate each and all of your contributions and please keep them coming :-).

The neck has been buffed clean with a light abrasive Dremel wheel followed by steel wool, Simple Green washed clean with water and followed up with 90% isopropyl alcohol. I’ve done this for the 2nd and 3rd attempt.

ill check again on the source because this does seem SO odd

 

Man, I thought the odds were good that the OEM hose was gonna fix it. The only other thing I can think of is that the casting cracked. Or maybe flawed and when you cleaned it up the flaw was revealed. Keep us posted.

 

As said above - are you absolutely sure it's not the WP seal leaking? I had to replace my WP in 2006 for a seal leak which was not obvious except there was coolant running down to the hose. After it was exposed by removing stuff to get at it, the seal leak coolant leak stain could then be seen.

 

It could be the hose clamps. Recommend you use the stock clamps. I had the same problem using aftermarket clamps (albeit not constant tension clamps)

As said above, the WP should also be checked

 

Leaking water pump would be the next thing I'd check as Dave mentioned.
Do a cooling system pressure test to try and hone in on the exact spot where the leak is coming from. I posted a good tool to buy recently in another thread. You're welcome to search for it.

 

Or could be the gasket between the water pump housing and the engine. in theory it could trickle down to the rad hose. That's a hard space to get a good look at, though.

I have seen the hose barbs for the radiator hose be really pitted and not seal well. But it sounds like yours should be pretty clean.

OEM hose clamps are the way to go on coolant hoses but if the hose clamp you are using is decent and snug it should be fine. Long term it could be a problem but for a static test in the driveway it shouldn't be leaking.

Keep at it!

Dale

 

At this point, I'd pick up one of those coolant system pressure test kits and apply some pressure to the system to see if it makes the true leakage source more obvious. You can typically get the test kit at your local auto parts retailer (Advance, Autozone, etc.) for free - just put up a credit card deposit & return tool for a refund.

 

Reporting back...it WAS the WATER PUMP!!

All I Can say is that it was hard to see and it took 35 minutes of laying under my car with 3 different inspection mirrors to conclusively see it coming coolant escaping the pump weep hole and snake it’s slithery trail to the top edge of the lower radiator hose.

so I’ve contributed to Mazda and two silicone hose suppliers inventory throughout in the past two weeks. And put on a new pump and gasket. And maybe entertained you all a bit.

Thank each one of you for your help. Truth be told, I was very discouraged. I’ve been working this car for 20 months—-I’ve added fewer than 120 miles since I bought it in July ‘18. Your analysis and troubleshooting and suggestions have provided technical counsel as well as encouragement.

My car has ZERO coolant leaks now. Off to Break-in!

 

WoohooO! Glad you got it identified and totally fixed up! Time for the fun part!!!

 

Fortunately the FD's water pump isn't too bad to change. Beats a piston engine car that you have to pull the timing belt and all that mess to get to!

Glad you figured it out!

Dale