K1500 Suburban Coolant Flushing

[Char]

I recently bought this 1999 Suburban with a 5.7L Vortek, I have been stalking the forum learning lots from you all. I am not too experienced with auto work, trying to learn

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I’m working on changing the fluids, first of all the coolant, which was low (reservoir empty), and lots of sludge in the radiator cap. Existing coolant is orange (DexCool?)
I tried opening the petcock, but it does not look right:

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Might be broken, or maybe a previous owner installed that? Any ideas how I can open this to drain the coolant?

The next thing I tried was removing the lower radiator hose to drain from there. I opened the clamp, but the hose would not budge. Any ideas on removing a stuck hose?

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Thanks!

 

[SUBURBAN5]

I've always loosened the radiator hose. They do tend to stick over time especially if original. Twist or use a hose pic to pry or widen the hose and it should slide off.. also I poured coolant flush through the radiator and drove around to let it circulate. Also run the rear heater and you should be good to drain and pour fresh coolant

 

[Pinger]

You are where I was just over a year ago with my 1999 Suburban setting out on changing all the fluids.
I had an issue with the drain plug on the radiator. I twisted it out with pliers and on replacing it was I was far from convinced it wasn't ruined. No problems though it sealed and has held but when I recently had to remove coolant - I chose not to disturb it again. Yours might be missing the tab I twisted on with the pliers though.

As per Suburban5's post, a bit of manipulation gets the big hose off its spigot. Try and get a small screwdriver in between the hose and where its gripping the spigot and work it round as far as you can after you've slipped the clip back up the hose out of the way. Once the seal is broken it comes off quite easily. There will at that point be a torrent of fluid and it isn't easily contained. In future I intend finding a way to syphon from the top of the radiator what is left after draining from the two plugs on the engine block - hint hint.

Before you dive into changing the coolant I'd recommend just topping it up and running the truck for a while to see if the level holds up. Mine didn't (obvious leaks at the front of the engine which find their way down to coat the crank position sensor) due to inlet manifold gasket leaks. I had my oil analysed and it showed coolant in the oil also so at that point I jumped and changed the inlet manifold gaskets. If you have the same and intend changing the gaskets this year, there's little point in changing the coolant now.

Lots of info on the forum re inlet manifold gaskets including which replacements to use and how to change them. Maybe not your problem, but if I was you I'd want to know the cooling system doesn't have any leaks before going much further.

Welcome along. I was where you were a year ago. Now I'm answering - not just asking - questions. This forum is a font of knowledge and the members here ultra helpful.

 

[Char]

Thanks for the replies mr Suburban5 and mr Pinger!

I have read about the intake gasket problem, so far I don’t see any of the signs I’ve heard about (milky oil, white smoke exhaust) but could be I’ll only see that when the gasket has really badly failed?

Originally the plan was to just change the thermostat. I had a mechanic inspect it, he said engine temp never got high enough, so I guess the thermostat could be stuck open? When I found the sludge I figured I should flush it all out and replace the coolant, then replace thermostat.

My plan was to then drive it a while and watch out for those intake gasket signs, then change oil and take a close look at that.

Might be worth preparing for the intake gasket change. Could that be in my wheelhouse, or better left to a professional?

thanks!

 

[Pinger]

The signs can be subtle. For mine, the first sign was coolant loss. The coolant in the oil was detected from the anti-freeze components rather than water content. The prospect of the coolant being dumped into the oil prompted me to change mine sooner than later.
In the pic below, at the rear (LHS) it can be seen where the coolant and oil could mingle and at the front RHS) where it leaked externally. Multiple failure points. When you replace your thermostat and the system runs hotter and at higher pressure, the more likely will leaks be. If present. Maybe your coolant tank needs topped up and nothing more.

See the link for a 'how-to'. If there's nothing there beyond your capabilities then it you can consider tackling it yourself. Points to watch for are the EGR pipe can be awkward and, getting the distributor back in and set exactly has to be considered. Most use the scan tool, I used a jig to get it back in its original position in the absence of the scan tool.

https://www.gmt400.com/threads/intake-gasket-replacement.118/

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[Char]

Ok I’ll take that advice, watch the coolant level, watch the oil condition, check for external leaks. Then I’ll get the system flushed out next weekend if it’s not looking like an intake gasket issue

I guess my weekend project is now transfer case fluid and mud flaps!

 

[HotWheelsBurban]

I recently bought this 1999 Suburban with a 5.7L Vortek, I have been stalking the forum learning lots from you all. I am not too experienced with auto work, trying to learn

You must be registered for see images attach

I’m working on changing the fluids, first of all the coolant, which was low (reservoir empty), and lots of sludge in the radiator cap. Existing coolant is orange (DexCool?)
I tried opening the petcock, but it does not look right:

You must be registered for see images attach

Might be broken, or maybe a previous owner installed that? Any ideas how I can open this to drain the coolant?

The next thing I tried was removing the lower radiator hose to drain from there. I opened the clamp, but the hose would not budge. Any ideas on removing a stuck hose?

You must be registered for see images attach

Thanks!

That looks like the plastic petcock. I think they're designed to use a special tool to get them out.
I also have a 99 Chevy C1500 Suburban, with the 5.7 vortec engine. I've changed the water pump and both hoses on mine; not too hard for someone with basic mechanical skills if you take your time. I agree with the other guys that the lower hose is a better way to drain the radiator, but it will come out fast and messy.
Dexcool coolant is designed to have a certain shelf life, and be changed periodically. It often doesn't, especially when the truck has been sold a few times, and that's when it gets that sludgy look you're seeing. This can also happen if some other type of coolant has been put into the system. Dexcool is the orange GM factory recommended stuff, and it does not like to mix with any other coolant types.
I too would refill the bottle, maybe just with water, and drive it a bit and watch the levels and gauges. If the water and oil levels stay good and the temperature gauge isn't showing it's running hot and the oil pressure is good, you should be okay for a while. My Burb has intermittent leaks, and eventually will need intake gaskets and the related fuel injection service, as it's got 197,000 miles on it. I'm trying to save money for that, and keep it going in the meantime. It's our only vehicle and 3 of us depend on it to get to work. So I have gotten into the habit of checking the oil and water every morning before we go anywhere.
Good luck with your "new" Burb, and welcome to the forum!

 

[PlayingWithTBI]

In future I intend finding a way to syphon from the top of the radiator what is left after draining from the two plugs on the engine block

Get one of these, you can suck out of the radiator, engine block or anywhere else (like your transmission through the dipstick tube). It is reversible so you can fill stuff too.

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[JohnDenver]

I’m getting ready for the same project on my 98 K1500 Suburban so I’ll add my couple of questions here. For doing a good flush, do you just need to have the rear heat on to have it cycle the whole system? Remove thermostat or leave in? Do you install a flush T (if so where), or just stick a hose in the radiator cap, or just just drain top off repeat? I’ll be replacing heater hoses anyway since I’m getting a leak somewhere around the regulator that sends coolant to the rear heater (replacing that and the plastic T connections also).

Mostly I’m trying to make sure I know if the rear heat complicates things.

Thanks! Hopefully also helpful to the OP

 

[Coveman]

Mileage on truck and fluids? pressure test your cooling system to find leaks. can borrow one if you dont want to buy. our burbs with rear heat use a lot of coolant, you might want to do several things at once depending on maintenance history: (I did all these at 150k / 20 years)

coolant flush and fill
intake gasket
radiator
hoses
heater core
water pump

remember to fill with coolant and distilled water. i also added the leak stop tablets gm uses after the flush.

At 22 years old, if these items are original it’s not if but when they’ll fail, so save some time and money banging them out at the same time

btw i’m a big fan of those fluid pumps, i held off on getting one for too long!