Radiator leak during cold weather start? (1 Viewer)

[awesomeissquid]

Over the weekend we took the truck up to the mountains for some snow activities. The temps got down pretty low (1°F/-17°C) overnight before we left so I let the engine idle to warm up while we finished packing. Just as we were getting ready to leave my partner noticed some red snow under the front end. I freaked out a bit, shut everything off, popped the hood, and found some coolant along the top of the radiator and under the front end.

I looked over everything to see if there was anything obvious, but nothing popped out. The overflow tank was also still half full. I restarted the engine to see if I could pinpoint it that way, but there was now no additional coolant leaking out. Confused, we decided to drive over the first mountain pass cautiously watching the engine temp on the ScanGauge to the nearest auto parts store. On the 15 mile drive with 2,000 ft. elevation climb the engine temp never got above 192°F and stayed pretty constant between 182°F-188°F. At the auto parts store I checked again and no coolant was leaking and the overflow tank still looked good. After letting the engine cool down I pulled the radiator cap and found it still full of coolant. From here we drove the 200 or so miles back home without issue. Checked the engine again today and still no apparent loss of coolant.

Maintenance wise the radiator was replaced in 2017 (@237k miles) and the coolant and hoses/clamps/tee's were flushed/replaced a year ago (@270k miles). Currently sitting at 275k miles.

So I am at a loss for what happened. At first I thought my radiator had popped, but with no additional loss of coolant and no overheating I cant think of how that would be possible. The only thing I can remember is when I first started the truck to let it warm up I heard an unusual noise under the hood for the first instant but then it went away (it might have been a pop?). Is it possible that something froze up with the low temperature and when the engine started it over pressurized the coolant system and it released some of the pressure out of the radiator cap? Other possibility was that maybe the cold temperature caused something to shrink enough to allow coolant to leak out until it warmed back up. Any thoughts on would could cause this or if I am missing something bigger all together?

 

[JunkCrzr89]

Well damn, the same exact thing happened to me yesterday morning after a night of temps down to -7*F I messaged @2001LC about this yesterday.

In my case, despite turning the truck on to warm up for 15 min while I shoveled snow, hot air was not coming out of the vents. I drove 2 blocks and watched temps rapidly climb to 212*F. Pulled over and shut it off, let it cool until temp was down to 190*F, then started it up again and drove 2 blocks back home. By the time I got home, heat started blowing out of the vents but engine temp was back up to 205*F. Problematically, the Lower radiator hose was still COLD. I also noticed coolant dripping off the skid plate onto the snow. Pulled it into the garage and dropped the skid plates, the entire lower A/T cooler tank of radiator was covered in coolant and dripping. Cleaned it off and waited but never found a leak or crack.

My conclusion was that the 2 yr-old OEM thermostat was stuck closed (lower rad hose cold despite 212* engine temp), resulting in some back pressure that released out of a crack or pinhole in the 2 yr-old radiator. I picked up a new tstat and radiator today, will finish installing tonight and report back.

 

[nissanh]

Well damn, the same exact thing happened to me yesterday morning after a night of temps down to -7*F I messaged @2001LC about this yesterday.

In my case, despite turning the truck on to warm up for 15 min while I shoveled snow, hot air was not coming out of the vents. I drove 2 blocks and watched temps rapidly climb to 212*F. Pulled over and shut it off, let it cool until temp was down to 190*F, then started it up again and drove 2 blocks back home. By the time I got home, heat started blowing out of the vents but engine temp was back up to 205*F. Problematically, the Lower radiator hose was still COLD. I also noticed coolant dripping off the skid plate onto the snow. Pulled it into the garage and dropped the skid plates, the entire lower A/T cooler tank of radiator was covered in coolant and dripping. Cleaned it off and waited but never found a leak or crack.

My conclusion was that the 2 yr-old OEM thermostat was stuck closed (lower rad hose cold despite 212* engine temp), resulting in some back pressure that released out of a crack or pinhole in the 2 yr-old radiator. I picked up a new tstat and radiator today, will finish installing tonight and report back.

The leak could be a result of a gap between rubber gasket holding the upper or lower tanks of the radiator and the aluminum core. Metal shrinks (/expands) faster than the rubber/plastic leading to small gaps.

During the cold months, I hardly find the lower hose is warm with interior heaters running. Once I turn off the interior heaters, I do find the lower hose is warming up.

 

[Spike555]

Are you 100% sure it was coolant and not ATF or power steering fluid?

My coolant is yellow, transmission and power steering fluid are red. If you’re using Toyota (red) coolant you would be hard pressed to tell the difference in the snow between the three just by looking at them on the ground.

 

[JunkCrzr89]

Are you 100% sure it was coolant and not ATF or power steering fluid?

Yes.

 

[awesomeissquid]

Are you 100% sure it was coolant and not ATF or power steering fluid?

My coolant is yellow, transmission and power steering fluid are red. If you’re using Toyota (red) coolant you would be hard pressed to tell the difference in the snow between the three just by looking at them on the ground.

Yes as well.

 

[JunkCrzr89]

During the cold months, I hardly find the lower hose is warm with interior heaters running. Once I turn off the interior heaters, I do find the lower hose is warming up.

It was cold even after running it with the heaters off, too.

 

[awesomeissquid]

Well damn, the same exact thing happened to me yesterday morning after a night of temps down to -7*F I messaged @2001LC about this yesterday.

In my case, despite turning the truck on to warm up for 15 min while I shoveled snow, hot air was not coming out of the vents. I drove 2 blocks and watched temps rapidly climb to 212*F. Pulled over and shut it off, let it cool until temp was down to 190*F, then started it up again and drove 2 blocks back home. By the time I got home, heat started blowing out of the vents but engine temp was back up to 205*F. Problematically, the Lower radiator hose was still COLD. I also noticed coolant dripping off the skid plate onto the snow. Pulled it into the garage and dropped the skid plates, the entire lower A/T cooler tank of radiator was covered in coolant and dripping. Cleaned it off and waited but never found a leak or crack.

My conclusion was that the 2 yr-old OEM thermostat was stuck closed (lower rad hose cold despite 212* engine temp), resulting in some back pressure that released out of a crack or pinhole in the 2 yr-old radiator. I picked up a new tstat and radiator today, will finish installing tonight and report back.

Haha, guess we were both lucky for New Years. So you had no coolant at the top of the radiator, just the lower portion? Look forward to an update when you get the t-stat out. Any plans to test it to see if it still works? I wonder if the cold could cause the t-stat to stick.

The leak could be a result of a gap between rubber gasket holding the upper or lower tanks of the radiator and the aluminum core. Metal shrinks (/expands) faster than the rubber/plastic leading to small gaps.

During the cold months, I hardly find the lower hose is warm with interior heaters running. Once I turn off the interior heaters, I do find the lower hose is warming up.

That is kinda what I am thinking happened since I had no leak after the initial warm up and the drive back home. I am still considering getting a rental pressure tester just to confirm that there isnt any leak.

 

[JunkCrzr89]

Any plans to test it to see if it still works?

Yes. I pulled it and the radiator a couple hours ago. Will test the tstat tomorrow.

 

[JunkCrzr89]

Quick update on mine: The upper tank is stained with coolant in multiple locations where it meets the aluminum, with no staining anywhere above.

Also some evidence of where coolant was dripping down the side the radiator to the lower tank.

I never found any evidence of a leak on the bottom end. So it appears that @nissanh was right and the upper plastic tank was no longer sealed well to the aluminum core, which didn’t come to light until freezing temps hit.

I dropped in a new Denso rad that I put fresh foam on, along with a new thermostat and o-ring. Will fill and bleed the system tomorrow, but hopefully good to go

Be jealous of the new OEM A/C lines that I installed back in the summer

 

[2001LC]

When cabin heaters does blows cool, this is the biggest clue coolant system is low. Stuck open thermostat has similar effect on cabin heat, where it blows warm. Properly working and coolant system full, it blow hot.

It could be some Radiators rubber seal between plastic & core, are shrinking in the cold. Not an issue I've seen, but possible.

Be interesting if you both check cap & thermostat. To see if they working as should.

BTW: 9 out of 10 time, I use OEM. 1 in 10 I use CSF radiators.

 

[JunkCrzr89]

When cabin heaters does blows cool, this is the biggest clue coolant system is low. Stuck open thermostat has similar effect on cabin heat, where it blows warm. Properly working and coolant system full, it blow hot.

It could be some Radiators rubber seal between plastic & core, are shrinking in the cold. Not an issue I've seen, but possible.

Be interesting if you both check cap & thermostat. To see if they working as should.

BTW: 9 out of 10 time, I use OEM. 1 in 10 I use CSF radiators.

In my case, after letting the truck sit overnight and checking coolant level the day after, the coolant was a little low (at the bottom of filler neck, but not down to the fins). So the low coolant level that you’re referring to is ruled out.

Just checked the 2 yr-old OEM thermostat by heating water to 93*C, dropping tstat in, and checking that it opened quickly and then gradually closed as water temp cooled to 82*C. The thermostat worked fine.

I don’t have a rad cap pressure tester but can prob source one locally. The rad cap is OEM and also just 2 years old, so I don’t suspect it’s faulty. Also, there was no blockage in the overflow tank hoses or cap, and the coolant level in the tank was halfway between L and H.

As of right now, my tentative conclusion is that the upper tank of the radiator lost its seal and allowed coolant to leak out and air pockets to enter the cooling system.

 

[awesomeissquid]

When cabin heaters does blows cool, this is the biggest clue coolant system is low. Stuck open thermostat has similar effect on cabin heat, where it blows warm. Properly working and coolant system full, it blow hot.

It could be some Radiators rubber seal between plastic & core, are shrinking in the cold. Not an issue I've seen, but possible.

Be interesting if you both check cap & thermostat. To see if they working as should.

BTW: 9 out of 10 time, I use OEM. 1 in 10 I use CSF radiators.

I have only checked the radiator level after the first mountain pass after letting the engine cool from 182F to 126F. The level was as high as it could be. The cap is about 1.5 years old and was purchased from Partsouq. I will check the level again tomorrow as it is raining again today.

I will test my radiator cap when I pressure test the coolant system. I will likely replace the radiator and test the themostat at that time. I am thinking between Koyorad, Denso, and Mishimoto Aluminum options.

 

[2001LC]

In my case, after letting the truck sit overnight and checking coolant level the day after, the coolant was a little low (at the bottom of filler neck, but not down to the fins). So the low coolant level that you’re referring to is ruled out.

Just checked the 2 yr-old OEM thermostat by heating water to 93*C, dropping tstat in, and checking that it opened quickly and then gradually closed as water temp cooled to 82*C. The thermostat worked fine.
View attachment 2882986

I don’t have a rad cap pressure tester but can prob source one locally. The rad cap is OEM and also just 2 years old, so I don’t suspect it’s faulty. Also, there was no blockage in the overflow tank hoses or cap, and the coolant level in the tank was halfway between L and H.

As of right now, my tentative conclusion is that the upper tank of the radiator lost its seal and allowed coolant to leak out and air pockets to enter the cooling system.

If you've an air compressor, you can test that the cap is with range. Blow air in reservoir hose to rad/cap. Have pressure turn it down to ~10PSI, air should not pass the cap. Turn to 15-17 PSI air should pass the cap.

So why wasn't cabin heat working, if level was okay!

I have only checked the radiator level after the first mountain pass after letting the engine cool from 182F to 126F. The level was as high as it could be. The cap is about 1.5 years old and was purchased from Partsouq. I will check the level again tomorrow as it is raining again today.

I will test my radiator cap when I pressure test the coolant system. I will likely replace the radiator and test the themostat at that time. I am thinking between Koyorad, Denso, and Mishimoto Aluminum options.

Checking level anytime other than after 8 hour cool down, is not very revealing. Unless very low.

 

[awesomeissquid]

Well I got curious and caught a break in the rain so I went out to take another look. Truck has sat since Saturday evening and it was raining today in the 50F's so no sun to warm anything up. Overflow tank was about an inch above the low level so it probably needs to be topped up. Radiator was still filled right to the top of the neck. Did find a few floating pieces of black plastic in there which I have no idea what they are from which is slightly concerning.

I also took some pictures to show in which locations I originally found the leaks on my radiator. Along the line marked with #1 I found a line of coolant. At the spot marked with #2 under the upper coolant hose I found a small puddle (size of a half dollar coin).

Looking from underneath there were some drips from the lower mounting bolts which I believe ran down from the top.

Looking closer at the top I do see some staining near the filler neck, but I am not sure if that is from this leak occurrence or a prolonged minor leak that has been ongoing.

 

[JunkCrzr89]

So why wasn't cabin heat working, if level was okay!

As I noted above, it did start working on the second startup to drive 2 blocks back home, but temp was back up to 205*F by the time I got there. Regardless, coolant level was REAL GOOD! Just to verify, I drained the radiator, reservoir, and block and got a total of 3.7 gallons out. I did not drain the rear heater or it’s lines, which account for at least 0.15 gal. The capacity is 4.05 gal, so 4.05 - 3.7 - 0.15 = 0.2 gal “low” or unaccounted for, which probably totals the amount that I lost from the radiator leak.

The one oddity that I did notice was that the coolant was very transparent light pink rather than transparent red. I think I may have mixed the Toyota LLC as 30:70 with distilled rather than 50:50 when I did the cooling system overhaul 2 years ago. We were living in Phoenix at the time where it’s hot as hell and I remember considering 30:70 coolant:distilled (for heat dissipation) but don’t remember if that’s what I decided on or not. Based on what came out, good chance I did that. We have since moved to CO and I never changed the coolant because I hadn’t hit the mileage interval yet. If my math is correct, a 30:70 mixture of coolant:distilled has a freeze point of around -17*C or +1*F. Sustained -7*F temps overnight likely caused the coolant mixture to freeze inside the radiator (or at least become slushy), which led to initially no heat, rapid rise in engine temps, and a leaky radiator. As the engine temp rose, a lot of that melted quickly, allowing the heat to work 10 min later when I started the truck up again. That’s my theory anyways, which, if true, means I’m an idiot for not changing the coolant when we moved to CO

 

[JunkCrzr89]

Final update on mine: Got everything buttoned up and filled with new Toyota LLC coolant at 50:50 mix with distilled. Drove around for an hour today and engine temps stayed between 183.3*F and 188.6*F, with the exception of a 5-second period when temps hit 190.4*F but dropped back down thereafter, which I think was a remnant air bubble. Will do the typical +8 hour nighttime cooldown followed by morning top off everyday for the next few days until all the air is out and the system is full.

@awesomeissquid sorry for hijacking your thread. Our coincidental, simultaneous misfortune fell in my lap Look forward to hearing what your results are, though.

 

[awesomeissquid]

Final update on mine: Got everything buttoned up and filled with new Toyota LLC coolant at 50:50 mix with distilled. Drove around for an hour today and engine temps stayed between 183.3*F and 188.6*F, with the exception of a 5-second period when temps hit 190.4*F but dropped back down thereafter, which I think was a remnant air bubble. Will do the typical +8 hour nighttime cooldown followed by morning top off everyday for the next few days until all the air is out and the system is full.

@awesomeissquid sorry for hijacking your thread. Our coincidental, simultaneous misfortune fell in my lap Look forward to hearing what your results are, though.

Glad you got it sorted!

I will be pressure testing my radiator tomorrow just to see if it holds, but will likely go ahead and replace the radiator since leaking at low temps isn't cool. Still reading other threads to figure out which option I will go with, but I have ruled out the Mishimoto aluminum over flexing concerns. Debating internally between a Koyorad or a OEM.

 

[JunkCrzr89]

Glad you got it sorted!

I will be pressure testing my radiator tomorrow just to see if it holds, but will likely go ahead and replace the radiator since leaking at low temps isn't cool. Still reading other threads to figure out which option I will go with, but I have ruled out the Mishimoto aluminum over flexing concerns. Debating internally between a Koyorad or a OEM.

OEM is best. I bought a Denso because it was in stock at my local Napa, whereas Toyota dealer couldn’t get an OEM for a week (possibly longer). I just didn’t want the downtime, but had that been a luxury at the moment, I would’ve gotten OEM.

 

[2001LC]

If you using KOYO or CSF. They tend to weep at lower goose neck. I've found, by filling casting groove with FIPG 1282B (any coolant rated FIPG, should do), weep can be mitigated. I let FIPG dry overnight before attaching lower hose.

CSF Rad & new OEM lower hose 1 year after install.

Filed off raised casting keeping shape as round as possible.

Filled in casting groove, using raise blade to form & smooth, then curing overnight.

99.9 % sealed, 1 year later.