Losing coolant but no apparent leak

Doug in NH · Nov 29, 2021

Hey all,
2019 Ram ProMaster 3500. 18 k miles.
Since mid summer I have been monitoring a drop in my coolant level. Put some white duct tape on the coolant reservoir and put a line and the mileage after every trip or two. I can drive 1000 miles and the level drops 1/8”. Or I can drive 500 miles and it drops 1/2”. Absolutely no visible leak. I took one of my wife’s white towels (don’t tell her) and would spread it out under the vehicle when I parked. Not a drop on it all summer. Took it to a local garage, they did a pressure test and didn’t get a drop of leakage. Took it to a Ram dealer and the same thing.
The oil looks like oil. No grey, no foaminess, or anything unusual.
Any ideas… where can it be going and how would I detect it? Any other tests the Ram dealer should have done?
Thanks!

crazykid1994 · Nov 29, 2021

My only other thought would be head gasket failure. There is a way to check for exhaust gas in the coolant.

Doug in NH · Nov 30, 2021

Thanks! Searched on that… found and ordered a kit to test for that. Will post the results this weekend.

crash68 · Nov 30, 2021

You could also have the oil tested, the moisture can be driven out but the coolant will show up in testing.

Doug in NH · Dec 7, 2021

I received the kit to check for exhaust gasses in the coolant from BlockTester.com. It requires removing the radiator cap and inserting the testing tool. Of course, there is no radiator cap on this engine. I spoke to the fellow at BlockTester... super helpful... and he said to try it on the surge tank anyway... it **should** work. That came up negative. He also pointed out that the leak could be on the intake side... so that the missing coolant would be going out the exhaust pipe.
This is actually a Winnebago Travato, built on the 3500. So I called Winnebago and they gave me the RAM fleet support #.
Called them. Very disappointing conversation. "If they don't detect a leak there's nothing they can do". "What about a head gasket leak?". "Did you tell them to run diagnostics on that?". "No... I told them I was losing coolant and wanted them to find the issue". "You have to TELL THEM what tests you want them to run" was her reply. Say whaaaaat? I have known mechanics that would punch me if I said "I am going to tell YOU what tests you need to run".
So... I need to go back to the dealership and tell them what tests to run, apparently. What tests would YOU request at this point, if this were your vehicle and RAM will be footing the bill? Pile it on!

jws123 · Dec 7, 2021

Doug in NH said:
I received the kit to check for exhaust gasses in the coolant from BlockTester.com. It requires removing the radiator cap and inserting the testing tool. Of course, there is no radiator cap on this engine. I spoke to the fellow at BlockTester... super helpful... and he said to try it on the surge tank anyway... it **should** work. That came up negative. He also pointed out that the leak could be on the intake side... so that the missing coolant would be going out the exhaust pipe.
This is actually a Winnebago Travato, built on the 3500. So I called Winnebago and they gave me the RAM fleet support #.
Called them. Very disappointing conversation. "If they don't detect a leak there's nothing they can do". "What about a head gasket leak?". "Did you tell them to run diagnostics on that?". "No... I told them I was losing coolant and wanted them to find the issue". "You have to TELL THEM what tests you want them to run" was her reply. Say whaaaaat? I have known mechanics that would punch me if I said "I am going to tell YOU what tests you need to run".
So... I need to go back to the dealership and tell them what tests to run, apparently. What tests would YOU request at this point, if this were your vehicle and RAM will be footing the bill? Pile it on!

Put some uv dye in the coolant it can be very helpful for hard to find leaks also if they dont find the issue this time find a new dealership.

Brian2081 · Dec 7, 2021

Good Evening All, 20 some years ago, I had a 1st year Neon that after a few years the coolant reservoir would just boil when I shut down the engine after a hard hey run.
Took the dealer 3 days to find the problem. Had a hair line crack in the head gasket between the combustion cylinder and a coolant passage.
Technician said there exhaust sniffer just barely registered coolant in the exhaust gasses.

Doug in NH · Jan 13, 2022

RESOLVED!
I **did** take it to a different dealership. They put it on the lift and found the leaking coolant source in about 5 minutes. It was leaking at a hose clamp.
Obviously very disappointed that TWO pressure tests at two dealers had failed to find it! I assume that the PT's are done on a cold engine, and the leak only happened at temp.
The reason that I hadn't noticed the coolant leaking (I had been putting a large white towel under the engine to try to find the leak) has to do with the fact that this was modified to be a Winnebago Travato RV. Thery install an extra alternator to charge the Lithium Ion batteries. Under the alternator is a plastic shield to protect it from road crap. Apparently the coolant would leak and pool in that shield... then when I drove off it would spill out on the road.
Thanks for all the input from everyone!

jogris · Jan 29, 2022

hey Guys
i have a 2016 Ram 3500 SRW 6.4 hemi
has anyone had a problem with clogged heater cores ??? ,, i have had a new one installed every fall since i have owned the truck,,, dealer say there is no answer to the clogged heater cores ... but something with the OAT coolant ,,, a couple weeks ago not only had new heater core but also a new radiator installed that was clogged also ,, called RAM and they say no one to talk too about the coolant problem... i flushed the system and put HOAT in as coolant ,, what does anyone think????

crash68 · Jan 29, 2022

@jogris is only properly mixed or pre-mixed Mopar OAT coolant being used? By properly mixed, either deionized or distilled water used with the coolant.
This is right from a Dodge mechanic "Chrysler says to only use the pre-mix coolant for any service/warranty work" this is due in part to too many issues with coolant system clogging up.

Elvira · Jan 29, 2022

Some leaks are very evasive. They can leak overnight with temperature changes when materials expand and contract. Possibly heater core and the small amounts are falling inside the heater box and evaporating to show no evidence. Perhaps pressure testing for a longer period of time and keeping an eye on pressure drop, both when warm and when cold. I have seen transmissions leak only over night, the aluminum would cool and the slight crack opened up, thus the leak over night. This could be the same scenario with coolant, many aluminum parts on an engine these days. Very small leaks being burned internally may not show physically on spark plugs or tail pipes as a white smoke or a deposit.

GTyankee · Jan 29, 2022

2013 & newer Rams leave the assembly line with Mopar OAT Coolant

HOAT coolant should never be put a 2013 & newer Ram

When OAT & HOAT are mixed, you get something like Maple Syrup mixed with Oatmeal

....................................................................

Doug in NH,
someone misinformed you

You mentioned that your Ram engine does not have a radiator cap. How would you add coolant after draining your coolant at 100,000 miles or 10 years

You do know that the coolant systems are pressurized & the Radiator Cap is what allows the system to pressurize.

The radiator cap is on top of the radiator, just as they have been for years.

Chances are you have a dust cover, called a Sight Shield, above the radiator, there is a trick to removing the cover without damaging it,
just watch a bit of this video, it shows how to properly remove the cover

Ram Truck Code: P1D73 AGS (Active Grill Shutter) performance

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bigcanoe1 · Sep 8, 2022

Doug in NH said:
RESOLVED!
I **did** take it to a different dealership. They put it on the lift and found the leaking coolant source in about 5 minutes. It was leaking at a hose clamp.
Obviously very disappointed that TWO pressure tests at two dealers had failed to find it! I assume that the PT's are done on a cold engine, and the leak only happened at temp.
The reason that I hadn't noticed the coolant leaking (I had been putting a large white towel under the engine to try to find the leak) has to do with the fact that this was modified to be a Winnebago Travato RV. Thery install an extra alternator to charge the Lithium Ion batteries. Under the alternator is a plastic shield to protect it from road crap. Apparently the coolant would leak and pool in that shield... then when I drove off it would spill out on the road.
Thanks for all the input from everyone!

Glad you found it. I suspect I have the same issue. My dealer has not been able to find it, but I can smell it and there are no spills on the ground. I am hoping to scope it with a camera first to see if I can find it without jacking it up to remove the plate. Did you simply tighten the clamp or replace the clamp? Thanks for the updates. I have the same rig and have heard about problems around the new alternator and belts hitting the hose.

Losing coolant but no apparent leak

Doug in NH

Junior Member

crazykid1994

Senior Member

Doug in NH

Junior Member

crash68

ACME product engineer

Doug in NH

Junior Member

jws123

Senior Member

Brian2081

Senior Member

Doug in NH

Junior Member

jogris

Junior Member

crash68

ACME product engineer

Elvira

Senior Member

GTyankee

Senior Member

Ram Truck Code: P1D73 AGS (Active Grill Shutter) performance

bigcanoe1

Junior Member

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