Continual coolant leak.

[Trickster29]

I have a 2002 suburban 1500 L59 5.3,

I recently got it diagnosed for a coolant leak. They said it was all leaking out of the usual water pump. I replaced the water pump. I'm still losing coolant somewhere. I'd love to order a coolant pressure tester. But it costs a fortune for one that's guaranteed to fit.

Getting loan tools from ethier autozone or o'reilly is literally not much better in terms of price.

I can't understand why a cap and a pump are so expensive.

Anyways. When I remove the radiator cap to check the level. As I have been for the passed couple days. It makes a hiss. As if its pressurized.. I can't understand if it's holding the air at a high pressure. That it is leaking.

Is it possible that air is still escaping the system and its not leaking at all?

We did drain and flush the system. So it does make sense that air would be stuck. But I wanna get another person's point of view.

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[Fless]

Are you sure that you're "losing" coolant? Is there any showing up outside of the engine? Since you drained the system, it could be that all that's needed is to go through the bleed procedure; you should be able to find that in a Haynes manual, or something similar.

Loan tools are just that. For virtually no net cost you can rent the pressure tester. Essentially you put up the money to buy it, then your money -- most, if not all, check the program rules at the parts place -- is refunded when you return it. If it's an expensive tool, I put it on a credit card and never put out any cash. As long as I return it in the allotted time, the refund shows up in the same cc statement and I'm out no money. That pressure test kit is expensive, IIRC it's about $100 in my part of the country.

 

[Trickster29]

Are you sure that you're "losing" coolant? Is there any showing up outside of the engine? Since you drained the system, it could be that all that's needed is to go through the bleed procedure; you should be able to find that in a Haynes manual, or something similar.

Loan tools are just that. For virtually no net cost you can rent the pressure tester. Essentially you put up the money to buy it, then your money -- most, if not all, check the program rules at the parts place -- is refunded when you return it. If it's an expensive tool, I put it on a credit card and never put out any cash. As long as I return it in the allotted time, the refund shows up in the same cc statement and I'm out no money. That pressure test kit is expensive, IIRC it's about $100 in my part of the country.

I didn't physically see any coolant. The tank itself does go down. But everytime I open it to refill it. It lets out air. An audible hiss is heard.

I know bleeding gets the air out of the system.

Do you think there's just air in the system?

I did not know that they refunded after. I guess I should read more. Thanks for that information.



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[Granprixfan]

Keep it topped off at the correct level and see if it really is going down or you are in fact you are still "burping" the system
Run it and cycle through the the front and rear heater settings on next drive.
Before starting it cold check it
When you get to your destination check it
if your running late to something and don't have time to check it do it when you get back to the parking lot leaks visible when it's really hot and as it cools...takes awhile depressurization to happen
I know you said that you don't see coolant but...
Check the hoses and your water pump, don't forget the plastic "T" fittings and metal firewall tubing for heater core all for slow drip...inside the cabin floor too
Do this for a few days keep note of levels don't just assume you have to throw money at it
Visually check without opening/removing cap
not to sound condescending but of course you'll get hiss if you unscrew the cap when it's even slightly warm, when hot you could get a trip to the ER.

 

[Trickster29]

Keep it topped off at the correct level and see if it really is going down or you are in fact you are still "burping" the system
Run it and cycle through the the front and rear heater settings on next drive.
Before starting it cold check it
When you get to your destination check it
if your running late to something and don't have time to check it do it when you get back to the parking lot leaks visible when it's really hot and as it cools...takes awhile depressurization to happen
I know you said that you don't see coolant but...
Check the hoses and your water pump, don't forget the plastic "T" fittings and metal firewall tubing for heater core all for slow drip...inside the cabin floor too
Do this for a few days keep note of levels don't just assume you have to throw money at it
Visually check without opening/removing cap
not to sound condescending but of course you'll get hiss if you unscrew the cap when it's even slightly warm, when hot you could get a trip to the ER.

Thanks I'll keep checking,

It just confuses me. How can something hold pressure for so long if it was leaking. I'm getting the hiss when its cold not when it's warm. I check it every night at 2 am when the engine has been sitting for a good while. (weird schedule.... Its just when I started checking it. So I decided to keep it every 24 hours)

BTW with how my tank is, it's very hard to tell without taking off the cap. Cause you may be able to see green coolant from the side. But if you look in there. There's actually nothing in there. And the hose is just sucking air. (this is when the water pump was leaking)

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[HiHoeSilver]

Have you let the truck run for a while with the radiator cap off?

 

[Trickster29]

Have you let the truck run for a while with the radiator cap off?

Yes, I did when I first did but I didn't do the procedure correctly. And I did again today, But this time following the manuals burping instructions like Fless suggested. Immediately after running the heater at full blast all the reserve coolant left the tank. I compensated with what I had left. Which got the tank a little below full. Let it run for about 10 to 20 mins. Saw that it was stable at that little below full.

I imagine that there is something plugging coolant from reaching the heater core until the heater is on...... Perhaps that seal wasn't perfect and coolent was slowly trying to fill the heater core.

Went to go buy more coolant. And a new radiator cap. I read if a radiator cap is bad. It's possible it may leak out via the overflow pipe while driving. This radiator cap does fit alot snugger.

I'm just trying to isolate any possible issue.

I also checked for missing cylinders while driving and coolant in the tail pipe. Neither of these excisted. I parked it on clean concrete and am waiting for it to cool off to top off the tank.

I picked the clean part of the driveway cause I thought it would be more obvious if it was leaking onto clean concrete. Vs where it's normally parked, which is full of fluids from past jobs.

To clarify, The engine ran for a 10 to 20 mins with the cap off with the heater on blast. It also ran all the way to autozone with the cap on. And ran all the way back to the house with the New cap on.

I know one of the members here said you shouldn't remove the cap when it's hot, aswell as the cap itself which I read prior to having him/her point it out, But I figured it was fine. This new 165F thermostat leaves it at 185F normally considering the boiling point of water is 212F (100C). I highly doubt it would be hot enough to explode on me.

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[HiHoeSilver]

Yes, I did when I first did but I didn't do the procedure correctly. And I did again today, But this time following the manuals burping instructions like Fless suggested. Immediately after running the heater at full blast all the reserve coolant left the tank. I compensated with what I had left. Which got the tank a little below full. Let it run for about 10 to 20 mins. Saw that it was stable at that little below full.

I imagine that there is something plugging coolant from reaching the heater core until the heater is on...... Perhaps that seal wasn't perfect and coolent was slowly trying to fill the heater core.

Went to go buy more coolant. And a new radiator cap. I read if a radiator cap is bad. It's possible it may leak out via the overflow pipe while driving. This radiator cap does fit alot snugger.

I'm just trying to isolate any possible issue.

I also checked for missing cylinders while driving and coolant in the tail pipe. Neither of these excisted. I parked it on clean concrete and am waiting for it to cool off to top off the tank.

I picked the clean part of the driveway cause I thought it would be more obvious if it was leaking onto clean concrete. Vs where it's normally parked, which is full of fluids from past jobs.

To clarify, The engine ran for a 10 to 20 mins with the cap off with the heater on blast. It also ran all the way to autozone with the cap on. And ran all the way back to the house with the New cap on.

I know one of the members here said you shouldn't remove the cap when it's hot aswell as the cap itself which I read prior to having him/her point it out. But I figured it was fine. This new 165F thermostat leaves it at 185F normally considering the boiling point of water is 212F (100C). I highly doubt it would be hot enough to explode on me.

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I'm thinking you just had an air bubble in the block and the core wasn't full yet. Betting you'll be fine now. Let us know. Also, you can slide cardboard under there to save your driveway from more spots and it makes new drips really obvious.

 

[Andre Downer]

One thing that works for me is to put the car (any of them) on an incline when doing this, to help the Air easily pass to the highest point.. Park on a hill with the front facing up hill and top it off, let it run, then rinse and repeat..

Souns like a burp issue, and youll also see if anything is coming out of the tail pipe.. If coolant (or cloudy sweet smelling smoke is coing out), you might be burning coolant or have a gasket failure.. Whats the temp inside show ..? Right at 210 degrees or higher?

 

[Fless]

FWIW, here is one burp procedure for my '04 Tahoe:

Refilling

12 To refill the system, install the thermostat and reconnect any radiator hoses.

13 Place the heater temperature control in the maximum heat position.

14 Be sure to use the proper coolant listed in this Chapter's Specifications. Slowly fill the surge tank with the recommended mixture of antifreeze and water to the FILL COLD mark.

15 With the surge tank cap off, start the engine and let it idle for about a minute.

16 Install the cap on the surge tank, but don't tighten it down (pressure must be able to escape). Raise the engine speed to approximately 3000 rpm in 30-second cycles until the engine reaches normal operating temperature and the thermostat opens.

17 Turn the engine off and remove the surge tank cap. If there is any hissing noise coming-from the tank, wait until it stops then remove the cap.

18 Start the engine and let it idle for one minute. Add coolant to the tank until the level is 1/2-inch above the FILL COLD mark, repeat Step 16, then turn the engine off.

19 Add coolant as necessary to bring the level to 1/2-inch above the FILL COLD mark on the tank. Install the surge tank cap securely.

20 Check the cooling system for leaks.​

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