Slight leak of coolant and ATF

[MatSLO]

I had the radiator replaced in September 2018.

Two weeks ago, I noticed that the coolant level in the expansion tank was noticeably lower than it should be. I topped it off and checked it every morning when the coolant was cold. It seemed OK for two weeks, right on the "Cold" line, until this morning, when it seems it's maybe a millimeter or so below normal.
The fitting of the upper tube into the radiator (passenger side facing the cabin, just below the radiator cap) is a bit wet, I guess it's losing coolant there.

What worries me a little more is that just today, I also noticed an ATF leak at the lower tube fitting (the one below the coolant line described above). The fitting is wet and when the truck is parked, it's dripping enough ATF to make a noticeable (albeit very small) puddle on the ground. ATF level on the dipstick looks OK.

Of course I'll have it looked at by my mechanic next week.
But I need some advice if this is serious enough to not drive the truck much until then - or is it still safe to go on a trip I was planning for tomorrow? (about 100 miles each way, mostly highway).

 

[454cid]

I had the radiator replaced in September 2018.

Two weeks ago, I noticed that the coolant level in the expansion tank was noticeably lower than it should be. I topped it off and checked it every morning when the coolant was cold. It seemed OK for two weeks, right on the "Cold" line, until this morning, when it seems it's maybe a millimeter or so below normal.
The fitting of the upper tube into the radiator (passenger side facing the cabin, just below the radiator cap) is a bit wet, I guess it's losing coolant there.

Do you mean the small line going to the expansion tank on the firewall, or a heater hose (I have a heater hose on my truck in that area). Either way that doesn't sound too serious, maybe carry a jug of anti-freeze with you.

What worries me a little more is that just today, I also noticed an ATF leak at the lower tube fitting (the one below the coolant line described above). The fitting is wet and when the truck is parked, it's dripping enough ATF to make a noticeable (albeit very small) puddle on the ground. ATF level on the dipstick looks OK.

The fact it's dripping enough to leave a puddle sounds concerning, to me.

Of course I'll have it looked at by my mechanic next week.
But I need some advice if this is serious enough to not drive the truck much until then - or is it still safe to go on a trip I was planning for tomorrow? (about 100 miles each way, mostly highway).

Can you put a wrench on it, and try to tighten it? Maybe it's just loose.... I've never had one loosen up. Would your mechanic take a few minutes to look at it quickly, if you explain you're going on a trip.... just to see if it's serious, or if it's a matter of simply needing to be tightened?

 

[MatSLO]

Do you mean the small line going to the expansion tank on the firewall, or a heater hose (I have a heater hose on my truck in that area)..

The easiest way to explain: the lines/fittings that the guy in the video below is doing from 10:39 onwards:

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[east302]

I don’t remember if the transmission cooler lines have o-rings or not, but maybe try tightening them up.

The fitting at the top is a spare on the vortec, provided by aftermarket manufacturers to make the radiator universal. Delco makes one that is correct and does not have the port.

The rubber caps that they install can (will) crack and leak after a few months. If you’re having this much trouble from a shop-installed radiator, it may be worth pressing them for a factory-style unit.

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[454cid]

I don’t remember if the transmission cooler lines have o-rings or not, but maybe try tightening them up.

I don't think they do. They're like fuel line fittings. The oil cooler side does use o-rings... at least on my 99 454 truck.

The fitting at the top is a spare on the vortec, provided by aftermarket manufacturers to make the radiator universal. Delco makes one that is correct and does not have the port.

My truck uses that port... that's why I asked the OP. GM did that wierd. I guess the 350 Vortec returns the heater circuit to the pump, and the TBI to the radiator. The 454 seems to be the opposite... well honestly, I don't know where the TBI 454 return goes to.

 

[Coveman]

Definitely not o-rings in the trans cooler lines on my 99. if they leak loosen them and check that they threaded on correctly, then carefully re-tighten them. the soft brass on the radiator should take the shape of the flair and seal without leaking.

 

[MatSLO]

Well, my mechanic tightened the fitting (I tried first, but do not have the right wrench).
Apparently, this is not the line from tranny but from the power steering pump. I'm running ATF in the PS pump (another mechanic filled it with ATF when replacing the PS pump)... I'll probably do a flush of the PS system as soon as I get my hands on some GM steering fluid (hard to come by in Europe)

 

[454cid]

Well, my mechanic tightened the fitting (I tried first, but do not have the right wrench).
Apparently, this is not the line from tranny but from the power steering pump.

Has this vehicle been converted to right-hand drive? If not, there should be no power-steering lines on the passenger side of the engine compartment.

While facing the truck, the power steering should all be on the right side.... which is considered the left side of the truck. I've never heard of a power steering cooler being inside the radiator. Mine is a standalone unit.

 

[MatSLO]

Yes, I also think it was the ATF line, not PS fluid. When I think about it, why would you need to feed the PS fluid into the radiator?...
Maybe my mechanic thought ATF level was fine - he checked it and it was fine, because I had added a little a few days before. I had performed a proper ATF check (as per the car's user manual) and found out it needed to be added (about 50-100 ml). I think I told him but maybe he didn't listen.

So, when he looked at the ATF level and it was OK, while the line/fitting was visibly leaking, he probably figured the red fluid came from the steering pump which also uses ATF.

Well anyway, the main thing is the ATF leak is stopped.

Now to figure out where the coolant is disappearing... (by looking at motor oil and coolant which are both fine, and no white smoke from the tailpipe), probably not through a gasket.

 

[5vortec7]

Check the quick connect heater hose fitting on the passenger front side of the intake manifold. I’ve had few of these be the source of slow coolant leaks