SOLVED: Diagnosing/replacing a leaky radiator + flushing coolant (for the inexperienced GMT400 owner)

[movietvet]

You said the radiator was dirty/filthy on the inside and therefore so is the rest of the system. Thermostat should be changed. I honestly don't see that the mixture can cause a problem in 20 miles. Why was it low to begin with? "a few years back"? How long and how old is the thermostat?

 

[slow_c1500]

A shop flushed the cooling system about 2 years ago. Thermostat is original if I had to guess. Not sure how it got low on coolant, it had the appropriate amount before. One day I just noticed that the reservoir was near empty.

Come to think of it, I did notice a small pool of coolant in the lower fan shroud before this all happened. After this, the pool was way bigger. I have a feeling that the rad is leaking, since it’s the only leak spot that would make sense for the coolant to end up where it has (Lower shroud, crevasse between the core support and upper shroud, along back of radiator, and on top of the intake tubing, probably from being blown by the fan)

Are there any other places it could leak where coolant would end up in those spots?

Edit: if I am trying to test the radiator for leaks and simultaneously flush the rest of the system, would it be best to just buy a cooling system flush kit and run water through it?

 

[454cid]

That’ll give you water-mains pressure on the radiator (and coolant system, including engine coolant passages / gaskets / seals, if connected, which I have seen done ).

It may not be a bad idea but I don’t think it’s a good one. Water mains around me run 50-55psi.

Get a coolant system test pump and use it to apply rated pressure (probably 15psi).

I did it, and blew a clamped radiator hose off my truck My city water pressure deadheads at about 60psi!

The truck is over 300K miles now, so it survived

At the time, it hadn't occurred to me that city water pressure was all that much. It shouldn't be difficult to temporarily set the radiator back in place and connect the hoses, and a real pressure tester from Autozone. I'd bet it's got a leak on a tank, Though.

 

[slow_c1500]

If I reconnected the radiator temporarily and used a cooling system flush kit, then would it be safe to use a water hose? Does the T adapter (that you connect the water hose to) have some kind of pressure regulator to make it safe to use a water hose? because I think that’s what you’re supposed to do

 

[GoToGuy]

What you've demonstrated so far is your not really understanding any advice given. If dissimilar coolant mix could cause a reaction in your radiator resulting in mechanical damage it wouldn't make it to market. If you wish to destroy your radiator go ahead. The cap relieves pressure over 15, psi. What do you think will happen at 25 and higher?
Using random unknown pressure regulation can result in a very bad day. It has been proven many times , you're so called good idea doesn't beat the laws of physics and mechanical engineering.
Good luck.

 

[1998_K1500_Sub]

Does the T adapter (that you connect the water hose to) have some kind of pressure regulator to make it safe to use a water hose?

It does not.

 

[454cid]

Those flush kits can't really be used per their instructions on our trucks if the heater core return line connects to the radiator. You would need to do some altering of the flow or the flush water mostly just goes through the heater core and not the engine.

Just reconnect the radiator with it sitting in place. The hoses will hold it and you can put a coolant pressure tester on it. AutoZone will let you borrow one....they charge you for it, then you return it and you get your money back. It's a regular thing they do, just ask them at the counter.

 

[slow_c1500]

What you've demonstrated so far is your not really understanding any advice given. If dissimilar coolant mix could cause a reaction in your radiator resulting in mechanical damage it wouldn't make it to market. If you wish to destroy your radiator go ahead. The cap relieves pressure over 15, psi. What do you think will happen at 25 and higher?
Using random unknown pressure regulation can result in a very bad day. It has been proven many times , you're so called good idea doesn't beat the laws of physics and mechanical engineering.
Good luck.

Sorry if it seems like I’m asking dumb questions, I was just unaware if the flush kit would or wouldn’t put too much pressure thru the system, because I’ve heard of people on this site recommend it.

 

[slow_c1500]

When I temporarily reconnect the rad and get a pressure tester, do I just fill the system with water and test it?
Also if I plan on flushing the block, should I do that before or after the pressure test?

 

[454cid]

When I temporarily reconnect the rad and get a pressure tester, do I just fill the system with water and test it?
Also if I plan on flushing the block, should I do that before or after the pressure test?

Yes, just use water.

The water you add, to do the pressure test, will help flush everything out. When you do the majority of the flushing really doesn't matter, but I'd suggest a mostly dry engine compartment when you do the pressure test, so you can see where the leak is... if it's all wet already, due to splashing, it could be harder to see a leak.

If your leak isn't immediately obvious, get a flash light and start looking closer/under/over/behind/wherever. The pressure tester will have a gauge on it, so if it's leaking you'll know, even if you can't see a leak, as the needle will go down. You might even want to leave it pressurized for a few minutes to see if it drops.