I could use some help sourcing a coolant leak

I just got back from a 1200 mile road trip up to Yosemite and have a coolant leak that I’m having a hard time sourcing where it’s coming from. Temps were in the 100's and I did alot of mountain pass climbs.

I replaced both radiator hoses and three heater hoses, Denso radiator and new thermostat and pink coolant. About 2000 miles ago.

Truck was running at normal temperature the whole time, never overheated. When I stopped to get gas, the first time about four or five hours into the trip I pop the hood just to check things out, and I noticed the coolant spatter on the hood and on the drivers side only. No visible dripping anywhere from the hoses, radiator overflow tank, etc. I did top off the coolant recovery tank two times and added about 1 to 2 cups each time.

So now I’m back home now ,pulled all the skid plates off got a pressure tester from AutoZone and still can’t see a visible leak. I pumped it up to 15 psi three times for 30 minutes each and no drips anywhere and no pressure drop, put the cap back on and revved it up to 3000 RPM and no drips at normal operating temperature .

The timing belt and water pump were done at 175,000 and I just hit 251,000 on the way home. My first guess is that it’s the water pump? But I’m not sure because there’s no weeping when it’s sitting and I can’t see any drips when it’s running or under pressure test, but the spatter seems to like it could’ve been coming from there the way the pattern is? When I had water pump failures on other trucks and cars, there definitely was drips under the car you could visibly see so that’s why I’m stumped right now. Not sure what to do so any input would be appreciated. I’m thinking about doing the water pump timing belt fan clutch pedestal, thermostat, serpentine… All the good stuff but don’t really want to do it if it’s just something minor.....I may wait until I hit 90 K since I’m only at 75K now . Thanks.

 

More photos

 

Have you replace the radiator cap? Doesn’t look oem or Denso in the photo

since you did the pressure test with no cap on.

 

More photos, last one shows the passenger side with no coolant spatter.

 

I think Jerry nailed it. When's the last time you replaced your rad cap?

BTW, engine bay looks awesome bro. Just gotta say that. Props where deserved.

 

Sorry, I did replace the radiator cap when I put in the new rad. OEM and seems to be holding fine, no visible moisture or weepmg or drips........It pretty much looks brand new,but I guess it's worth a shot. Do these water pumps weep when going bad?

 

Faulty cap? Legitimate OEM from a dealer? Still have the previous to swap in?

Ever have someone look under the hood with it open while you push 3k RPM in park, while the engine is hot after a 10-15 minute drive?

Clearly it's something on the driver's side, and it's high enough up that it's able to coat things below, and hit the firewall, but it's not putting anything on the passenger side of the bay. I'm thinking either cap, or a high leak where the rad is capped.

I can't tell you how many times leaks have been found while the engine is under load and hot, which didn't otherwise appear during idle.

 

I would look for hair line cracks in the recovery bottle.

 

Here’s a picture of of the radiator cap… The coolant recovery tank is old, but I did pull it out and give it a once over and nothing seemed wrong with it

 

Doesn’t the oem cap have a D on each side for Denso?

 

So I guess I’ll get a new radiator cap, clean it all up and drive it up to temp and have my son rev it while I’m checking it out. It has me stumped.

 

This is mine

 

AISIN THT015 (Standard Replacement) 180°F Info
OE Temp



AISIN Warranty Information
12 months/12,000 miles

This is the one I bought from Rockaoto, I think it's out of stock mow as I just checked now.....

 

Looks like the center part of your cap has come apart at some point and now is in the radiator.

 

I bought the rad. cap from Rockauto also, maybe it wasn't OEM? It only has 2000 miles on it but I will get a new one from the dealer

 

Order a Denso cap from rockauto. Looks like the middle of your cap is missing inside the radiator

 

That's the t-stat, not the cap.

 

^ this.

The missing part is what opens as the radiator cools to let air escape and suck fluid back in.

Your spray is from the overflow bubbling/over filling while driving.

 

Actually I don’t see a Denso part on rockauto anymore and I can’t find the part number on Denso website but here is the oem part number. I thought I bout a Denso one but I got oem.

Toyota part number 16401-20353

 

Are you sure you got it from Rock Auto? (Re-check your order.)

That ND logo on the left is the old Denso logo. The company was originally called Nippon Denso. According to Google, they changed the name in 1996.



Is it possible that's the old cap? If not, it could be counterfeit -- not likely if you got it from RA, but if it came for ScAmazon or some other source...?

Agreed.

Should look something like this:

 

For what it's worth, this is what the cap looks like on my 2000 AC.
Note the Nippon Denso logo.
I presume it's the original, but I don't know as I bought the truck used.

 

Also, there are 3 little coolant hoses behind the timing belt. I change them every time I do a timing belt.

 

Picked up the cap, does sayND on it , but it’s the higher pressure one. it does have the extra tab on it. I guess that fell off on the other one . We’llsee how it goes.

 

Back side

 

When I lived in Japan it was Nippon Denso so I think ND is correct but so it D

 

Disregard this, was making sure you were aware it is higher pressure but I see it in your post now. Not sure that it will cause any issue or not, never tried one.

 

Did you get that cap at the dealer? I've never seen a Toyota part packaged that way.

 

I think because it's a TRD branded part it got special packaging. It has the normal label on the plastic bag.

 

YES, Toyota Parts Online.com and the picked up at my local dealer. Maybe because it's TRD model in packaged that way? I live in San Diego and there is a huge Toyota parts distribution warehouse in Riverside CA about 1.5 hours away. Can order in the afternoon and receive at local dealer at 2-3 o'clock next day.

 

Cleaned up all the sprayed coolant and installed the new cap ast night. Drove to work at five in the morning no spillage but driving home this afternoon 23 miles in about 80° weather. I did get some. I think my next step is to replace the coolant recovery tank. I called the dealer because I couldn’t find the part number active and it is discontinued 16470–0F010. Rock auto has a Dorman one available. I may pick that up. Thanks for all the input. Any other suggestions?