NEED HELP Coolant Leak

therealsethallen

Original poster
Member
Sep 20, 2015
501
Western Mass.
So I put a new serpentine belt on my truck Saturday afternoon, and it's got a phantom coolant leak. It was a tiny bit below the cold fill mark, and I don't recall it ever being right at that mark, if I'm honest. I drove a cumulative 200 miles since I noticed it was low. Today, I popped the hood, and the tank is significantly more empty than it was Sunday. I smell coolant when the engine is hot every now and then, and not much more than that. It was 25 degrees yesterday morning and the heat cranks. It's had a P0128 code for about two weeks now, I have a thermostat ready to go in, too. The only line missing any clamp was the radiator to expansion tank return line, except it's tight and doesn't appear to leak. The water pump also doesn't appear wet.

Any tips out there?
 

littleblazer

Member
Jul 6, 2014
9,265
Radiator end cap would be my next guess. If it's leaking you can pressure test the system and if there is a hole you can track it down.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
I smelled coolant from mine from the time it was new. Never any drips, but, I did tighten the clamps a few times.
Also, two years in a row, I came home after two week vacations, and the coolant tank was down about a half inch. Not a drop or puddle to be found under the truck.
Never did figure out where it went.
 
Last edited:

littleblazer

Member
Jul 6, 2014
9,265
End cap? I'm not familiar with the term.
Radiator has cores those tubes dump into the ends of the radiator or the end cap. One on top one on bottom. One holds the hot engine coolant and the other the cooled. Mine is leaking pretty bad to the point that I can smell it when I get out of the truck but it doesn't drip or anything. I don't see the telltale dried coolant anywhere though.
 

northcreek

Member
Jan 15, 2012
3,310
WNY
I smelled coolant from mine from the time it was new. Never any drips, but, i did tighten the clamps a few times.
Also, two years in a row, I came home after two week vacations, and the coolant tank was down about a half inch. Not a drop or puddle to be found under the truck.
Never did figure out where it went.
Same for me, I've smelled coolant from day one, usually as it's heating up but, it is never down on coolant.
I've done everything imaginable to try and stop it and have had no luck. I just did a pressure check and it held 15 psi forever...:confused:
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
My vote is water pump if it's never been done. Super hard to find a leak on the pump because it's hidden behind the pulley.

Will just have to check her over extremely well.
 
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therealsethallen

Original poster
Member
Sep 20, 2015
501
Western Mass.
The water pump has a very small amount of play in it, suppose I may as well replace it when I have the alternator off to to the thermostat this week. I'm about to roll over 170k now, and I did a water pump at 140k a little under a year ago.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I went through two pumps. Installed a Gates when I replaced the engine and it went a couple of years later. ACDelco went in and it has lasted since.

You could use a UV dye and light to try and find the leak.
 
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