Coolant Leaking From Radiator Cap

[Joespot]

Having an issue with coolant leaking from my radiator cap while sitting at idle for extended periods of time (approximately 15-30min). The digital temp display reads anywhere from 199-201-203. I know my electronic cooling fan is not working and I will be replacing it in a couple of days, but it has been out for several weeks now and I just now started having this leaking coolant issue. The cap only leaks when at idle and not daily driving.... Note, radiator and cap was replaced about 6 months ago because it have a small crack in it around the mounting ear. I have already replaced the radiator cap again and still have the same results. Any suggestions on troubleshooting this would be extremely helpful. 2018 RAM 1500 Sport 4x4 5.7L V8...

 

[1999 White C5 Coupe]

Having an issue with coolant leaking from my radiator cap while sitting at idle for extended periods of time (approximately 15-30min). The digital temp display reads anywhere from 199-201-203. I know my electronic cooling fan is not working and I will be replacing it in a couple of days, but it has been out for several weeks now and I just now started having this leaking coolant issue. The cap only leaks when at idle and not daily driving.... Note, radiator and cap was replaced about 6 months ago because it have a small crack in it around the mounting ear. I have already replaced the radiator cap again and still have the same results. Any suggestions on troubleshooting this would be extremely helpful. 2018 RAM 1500 Sport 4x4 5.7L V8...

At idle, you have very slow coolant flow and no “ram air” effect through the a/c condenser and radiator (to cool the coolant without the cooling fan operating). There is also a heat-soak condition. That is why the temperature increases close to or at an engine overheat situation, pushing engine coolant out.

 

[Joespot]

So I'm assuming that correcting my faulty fan issue should help fix the issue...thanks.

 

[EdGs]

Crack in the mounting ear? On the radiator? The cap? Can you show a pic?

If your electric fan is not working, I hope you replace it ASAP. Don't take chances, it will bite you at the worst time.

Keep us posted.

 

[04fxdwgi]

For $32 bux shipped, get a radiator / cap tester from amazon, pump up the pressure and find the leak. Easy Peasy.

Amazon.com: HZAUTOS 14PCS Pressure Leak Tester Tool Kit, Radiator Pump Pressure Tester Kit for Automotive Cooling System Water Tank Leakage Detection : Automotive

Buy HZAUTOS 14PCS Pressure Leak Tester Tool Kit, Radiator Pump Pressure Tester Kit for Automotive Cooling System Water Tank Leakage Detection: Pressure & Vacuum Testers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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[Joespot]

Crack in the mounting ear? On the radiator? The cap? Can you show a pic?

If your electric fan is not working, I hope you replace it ASAP. Don't take chances, it will bite you at the worst time.

Keep us posted.

Will do. As soon as i said it didn't leak after running, well you know what happened. Got home from a 30 minute drive and there was coolant leaking out at the cap and you can see where it was spraying out pretty good. Going to change the thermostat tonight and wait for the replacement fan that should arrive tomorrow. Hopefully once i get both changed, I won't have any further issues. The engine temp never read over 210 while driving home today (82 degrees out). I also ordered the radiator cap tester that suggested..stay tuned.....

 

[EdGs]

Will do. As soon as i said it didn't leak after running, well you know what happened. Got home from a 30 minute drive and there was coolant leaking out at the cap and you can see where it was spraying out pretty good. Going to change the thermostat tonight and wait for the replacement fan that should arrive tomorrow. Hopefully once i get both changed, I won't have any further issues. The engine temp never read over 210 while driving home today (82 degrees out). I also ordered the radiator cap tester that suggested..stay tuned.....

Test that new thermostat first. Put it in a small pot of water on the stove. Using a meat thermometer, watch your water temp as the water heats up and note where the thermostat starts to and gets to fully open.

Apparently there's alot of duds these days. Doesn't surprise me.

 

[CanuckRam1313]

Will do. As soon as i said it didn't leak after running, well you know what happened. Got home from a 30 minute drive and there was coolant leaking out at the cap and you can see where it was spraying out pretty good. Going to change the thermostat tonight and wait for the replacement fan that should arrive tomorrow. Hopefully once i get both changed, I won't have any further issues. The engine temp never read over 210 while driving home today (82 degrees out). I also ordered the radiator cap tester that suggested..stay tuned.....

As for coolant top up, use only MOPAR coolant and either get their 50/50 premixed or their concentrated and mix 50/50 with distilled water only.

 

[EdGs]

As for coolant top up, use only MOPAR coolant and either get their 50/50 premixed or their concentrated and mix 50/50 with distilled water only.

^^^^^This^^^^^

68163848AB OAT Concentrate (mix wth 1 gallon DISTILLED water, and you'll have 2 gallons of 50/50 coolant for not much more than 1 gallon of premixed)
68163849AB OAT 50/50 premixed

You might get these part numbers with an AC suffix, it's an updated part or different mfr. Same stuff.

 

[Joespot]

Well, I replaced the electronic cooling fan and put everything back together. Ran the truck for a while, good temp, fan is cutting on/off, thermostat working, etc. All this was when I still had the burp kit on. Well, I put the radiator cap on and ran the truck for about 10 minutes and wouldn't you know....damn pin hole at the neck of the fill spout. You could barely see it bubbling, so I'm guessing without my elec fan not working, it got hot and the pressure was high and the coolant took the path of least resistance, right out the pin hole.. It was shooting up into the cap so hence the reason I thought it was the cap becuase it was always dripping with coolant. Pulled it all back apart, returned the 5 month old radiator for a replacement, put it all back together and......knock on wood, it's running great now...Good news is, I am very good with removing the radiator/fan clutch/elec fan/etc....

 

[EdGs]

Thats crazy having a pinhole like that.

Glad you found it. Keep checking your coolant levels.

When I replaced my radiator, it took me several heat cycles with adding several ounces of coolant each time before I got all the air out of the system.