Need help with a coolant leak

[Chubbs]

2003 yukon 5.3, vin (Z) flex fuel with 140,000 something miles.

i can really use tips & suggestions for tracking down a coolant leak before I go running around like a chicken with its head cut off, making 2 or 3 runs back & forth across town.

i noticed the surge tank was 1/2 low when i did a random check a week ago: whatever the leak it isn’t hitting the ground so i’ve been looking around. the top of the engine has dust and dirt on top so now it looks wet like mud. — this is looking at it standing on the pass side looking on top of the engine, very front. really the only place the manifold valley is visible.

i’m assuming that whatever needs replacing up there is fairly common and several of guys will all point to the same 1 or 2 diff possible offenders.

i don’t own a pressure kit and wanting to skip the PIA driving around but i can always rent 1 if my 1st attempt at repair-replace fails. i would still need to invest hours cleaning the engine off properly even if i had the test kit and a bunch of stuff moved out the way. it’s prob easier for me to just replace everything with a coolant fitting or gasket on the top end

i want to add coolant and finally decided on the Zerex orange OAT “for American vehicles” including i think 1995+ GM.

the only thing i haven’t serviced on this truck is the coolant. coolant systems are my NEMESIS and i’ve been putting that off. i’ve owned it for 1.5 years now and i assume the red coolant as seen in the surge tank is OEM Dex.

has anyone added the zerex orange to red dex cool? i’m not trying to flush this thing, just top it off.

FYI it looks like the zerex orange used to be labeled zerex dex cool until they rebranded it. says safe for dex cool vehicles but i don’t know if that means after a full system flush or compatible with other “OAT” dex cool manufacturers.

they had a prestone pink label dex cool up there, too but shouldn’t it all be the same and safe to mix?

so what to replace around the intake manifold that could be leaking coolant and combining/mixing zerex orange with whatever type of dex cool already in the truck. thanks for reading! i appreciate any & all feedback

 

[OR VietVet]

Get a pressure test kit and do that first. Just because you say it is not hitting the ground does not mean it isn't. Pressure test warm and cold engine. The wet you see could be from somewhere you are not seeing now and blowing back to that area. They are inexpensive to buy and can rent after calling around to see who has one instead of doing all that driving you talk about. There are numerous areas where you could be leaking, including internally. Check the oil fill cap and oil dipstick for sludge build up. That could indicate head gasket problems. The orange or red coolant should all mix fine. Check the seams of the radiator. May have to remove or loosen some shrouding to see. Pressure test after repair is another good reason to have your own tester. When you look in the reservoir bottle is it clean or does it have sludge in it too. You could be leaking at the rear area if you have rear heat. Basics first and stop assuming.

 

[BG1988]

2003 yukon 5.3, vin (Z) flex fuel with 140,000 something miles.

i can really use tips & suggestions for tracking down a coolant leak before I go running around like a chicken with its head cut off, making 2 or 3 runs back & forth across town.

i noticed the surge tank was 1/2 low when i did a random check a week ago: whatever the leak it isn’t hitting the ground so i’ve been looking around. the top of the engine has dust and dirt on top so now it looks wet like mud. — this is looking at it standing on the pass side looking on top of the engine, very front. really the only place the manifold valley is visible.

i’m assuming that whatever needs replacing up there is fairly common and several of guys will all point to the same 1 or 2 diff possible offenders.

i don’t own a pressure kit and wanting to skip the PIA driving around but i can always rent 1 if my 1st attempt at repair-replace fails. i would still need to invest hours cleaning the engine off properly even if i had the test kit and a bunch of stuff moved out the way. it’s prob easier for me to just replace everything with a coolant fitting or gasket on the top end

i want to add coolant and finally decided on the Zerex orange OAT “for American vehicles” including i think 1995+ GM.

the only thing i haven’t serviced on this truck is the coolant. coolant systems are my NEMESIS and i’ve been putting that off. i’ve owned it for 1.5 years now and i assume the red coolant as seen in the surge tank is OEM Dex.

has anyone added the zerex orange to red dex cool? i’m not trying to flush this thing, just top it off.

FYI it looks like the zerex orange used to be labeled zerex dex cool until they rebranded it. says safe for dex cool vehicles but i don’t know if that means after a full system flush or compatible with other “OAT” dex cool manufacturers.

they had a prestone pink label dex cool up there, too but shouldn’t it all be the same and safe to mix?

so what to replace around the intake manifold that could be leaking coolant and combining/mixing zerex orange with whatever type of dex cool already in the truck. thanks for reading! i appreciate any & all feedback

could try the pepper trick it will plug tiny holes ..

Don't use STOP leaks I ruined an engine using it caused even more damage i ended up selling the car for scrap after that..


just use prestone Dexcool certified(make sure it says it on the bottle) I would buy the full concentrate for 2$ more then mix it with distilled water it's not complicated it's 50/50 after all this is why it pays to keep a old coolant bottle on hand they never go bad(the 5 years is inside an engine not sitting in a bottle as it's not subject to heat cycles of the engine) in an engine the coolant wears out

 

[wjburken]

I’m with Ron on this. Don’t just throw parts at it. Take the time to understand the problem first and then fix/replace what is needed.

Spray down your engine and get it cleaned up - Top and bottom. Get a pressure tester - rent or buy. Get a flash light and while the pressure tester is on, starting looking all over for coolant to be were it’s not supposed to be. This includes inside the vehicle under the passenger side dash. Don’t forget to check the oil like Ron said.

Are you smelling coolant when you get out of the vehicle at home? Any odor inside the vehicle? Any moisture around the water pump?

Check things out and let us know what you find.

 

[Chubbs]

i took a few pics. water pump area looks dry, as does the heater hose connections and major hoses.

it does appear to be all damp on top of the engine though.

i know all you guys want me to pressurize the system and it doesn’t escape me that it would be proper course of action. i’ve done every bit of service, maint & repairs on all 3 vehicles we’ve had in the past 4-years.

i’ve never actually had to use a pressurizer even with all the diagnosing of coolant-loss related issues. i’m just not familiar with the system and serviceable parts on this GM truck. the top end looks like a cluster f*ck of crowded mess.

back when i had access to the Chiltons Online i could track down anything given the thoroughness of the data including diagnosis. OTH this little Haynes repair guide for 99-06 just glosses over the big stuff in chapter 3 ‘cooling & hvac’ - it’s pathetic

 

[Doubeleive]

View attachment 238307 View attachment 238308 View attachment 238309 View attachment 238310 View attachment 238311 i took a few pics. water pump area looks dry, as does the heater hose connections and major hoses.

it does appear to be all damp on top of the engine though.

i know all you guys want me to pressurize the system and it doesn’t escape me that it would be proper course of action. i’ve done every bit of service, maint & repairs on all 3 vehicles we’ve had in the past 4-years.

i’ve never actually had to use a pressurizer even with all the diagnosing of coolant-loss related issues. i’m just not familiar with the system and serviceable parts on this GM truck. the top end looks like a cluster f*ck of crowded mess.

back when i had access to the Chiltons Online i could track down anything given the thoroughness of the data including diagnosis. OTH this little Haynes repair guide for 99-06 just glosses over the big stuff in chapter 3 ‘cooling & hvac’ - it’s pathetic

you need to look under the truck and under the water pump, fluid will travel down not up

 

[OR VietVet]

Hot coolant will evaporate pretty quick if it is a very small leak. Remember, the hottest the engine is will be when you shut it off and then it does what is called a "hot soak". If the coolant is low in the upper end of he engine it will just seep steam out. Low places like the water pump can leak one minute and stop the next. You need a pretty good leak to make a puddle to see. If is just a very small drip you may never see it because it hits on components below it and never hits the ground. Like Wes said, look under the vehicle as well and look for the corrosive stain at the weep hole on bottom of pump and any low areas that contain coolant when it is moving around inside the cooling system. It could be something like a seam leak at the radiator. I sure would like to see a pic of this wet top of engine.

If in fact it is coolant that is the wet spot on top then you have other items holding coolant up there or an intake leak that pools at the top or even leaking down the back of the engine. remember, the lines under the vehicle if you have rear heat.

 

[Doubeleive]

Hot coolant will evaporate pretty quick if it is a very small leak. Remember, the hottest the engine is will be when you shut it off and then it does what is called a "hot soak". If the coolant is low in the upper end of he engine it will just seep steam out. Low places like the water pump can leak one minute and stop the next. You need a pretty good leak to make a puddle to see. If is just a very small drip you may never see it because it hits on components below it and never hits the ground. Like Wes said, look under the vehicle as well and look for the corrosive stain at the weep hole on bottom of pump and any low areas that contain coolant when it is moving around inside the cooling system. It could be something like a seam leak at the radiator. I sure would like to see a pic of this wet top of engine.

that's exactly where the o'ladys suburban is leaking, the bottom of the water pump, it's coming out of the front bearing seal (I think), looses about 1/2 gallon every 2-weeks, just been too lazy to fix it yet, lol, you can barely see a few droplets flowing under the very bottom of the pump doesn't leak on the ground

 

[OR VietVet]

that's exactly where the o'ladys suburban is leaking, the bottom of the water pump, it's coming out of the front bearing seal (I think), looses about 1/2 gallon every 2-weeks, just been too lazy to fix it yet, lol, you can barely see a few droplets flowing under the very bottom of the pump doesn't leak on the ground

Seen it happen that way many times. Coolant, especially very hot coolant, sometimes just doesn't hit the ground. The ambient temp can also make a difference. The colder it is outside the quicker the leaking hot coolant can evaporate. Chasing coolant leaks can be a PITA for sure. Even if it is easy to find, you still have to look forward to the cost of parts and labor to repair. Damn these vehicles we love soooo much.

 

[iamdub]

The highest point on the front of the engine that would have coolant is the throttle body. Check the small hoses going to each side of it. Next highest would be the coolant crossover ("steam vent") tubes. Pop off the intake duct so you can see and check these items.

 

[Chubbs]

here in dallas, the air temp changes 40-50 degrees. it was 70 deg on Fri and snowing Sat morning. whenever this happens, something leaks on at least 1 of our vehicles. the major temp swings are ******* seals with 200k miles and/or a good 15-years on them.

her 2008 the belt was squeaking on super cold mornings. i correlated that with a weeping water pump. it leaked when the temp changed so much so i went & replaced that even though the bearing was still tight. hated to do it only bc of the PIA coolant refill & air pockets that gave me hell.

i will remove the plastic guard and get a better look at the WP tomw if it warms up some. i’ve been under there 2-3 times looking for the leak. it’s all wet on the oil pan but i think it was dry up at the front.
FYI the oil pan was bone dry up until 2 weeks ago but both oil & coolant loss had occurred. i’ve never had to add oil bw changes and the coolant i’ve topped off with about 1/2 cup distilled water 2x in 1.5 years and neither was recent. it hasn’t lost any oil at all since i added 2 weeks ago (i checked yesterday) but i’m @ 5% on engine oil life and replacing it this week. i will be sure to check the level before i drain it to see if anything leaked after this cold front today.

will update tmw of anything found on further inspection. somebody asked about pics. pics are posted above in my last post

 

[Chubbs]

The highest point on the front of the engine that would have coolant is the throttle body. Check the small hoses going to each side of it. Next highest would be the coolant crossover ("steam vent") tubes. Pop off the intake duct so you can see and check these items.

the info i was waiting for. thank you sir!

 

[HiHoeSilver]

here in dallas, the air temp changes 40-50 degrees. it was 70 deg on Fri and snowing Sat morning. whenever this happens, something leaks on at least 1 of our vehicles. the major temp swings are ******* seals with 200k miles and/or a good 15-years on them.

her 2008 the belt was squeaking on super cold mornings. i correlated that with a weeping water pump. it leaked when the temp changed so much so i went & replaced that even though the bearing was still tight. hated to do it only bc of the PIA coolant refill & air pockets that gave me hell.

i will remove the plastic guard and get a better look at the WP tomw if it warms up some. i’ve been under there 2-3 times looking for the leak. it’s all wet on the oil pan but i think it was dry up at the front.
FYI the oil pan was bone dry up until 2 weeks ago but both oil & coolant loss had occurred. i’ve never had to add oil bw changes and the coolant i’ve topped off with about 1/2 cup distilled water 2x in 1.5 years and neither was recent. it hasn’t lost any oil at all since i added 2 weeks ago (i checked yesterday) but i’m @ 5% on engine oil life and replacing it this week. i will be sure to check the level before i drain it to see if anything leaked after this cold front today.

will update tmw of anything found on further inspection. somebody asked about pics. pics are posted above in my last post

I would definitely send a sample of the oil to Blackstone for analysis, especially since you're so close to changing it. On top of all of the other reasons, you will know for sure if there's coolant in it.

Over the years, I have had various coolant leaks on my Tahoes. It usually starts with me smelling it when I get out after a drive. If it's a slow leak (and no signs in the oil), I simply keep an eye and fill as needed until it reveals itself. Most often, it's while idling. I just let it idle in the driveway while I'm doing something else, watch it for a bit every few minutes, and eventually I see a puddle or a drip.

 

[Chubbs]

I would definitely send a sample of the oil to Blackstone for analysis, especially since you're so close to changing it. On top of all of the other reasons, you will know for sure if there's coolant in it.

dang! this why i hardly ever post on forums. get people to thinking the worst.

for SURE coolant is not mixing with engine oil.

i just wanted to know what all can leak coolant up on top of the engine. and if anybody mixes Zerex orange with OEM dex cool.

 

[HiHoeSilver]

dang! this why i hardly ever post on forums. get people to thinking the worst.

for SURE coolant is not mixing with engine oil.

i just wanted to know what all can leak coolant up on top of the engine. and if anybody mixes Zerex orange with OEM dex cool.

Not thinking the worst, just saying it's a perfect time to send a sample. Not only will you confirm what you know about your heads (or gasket), but you'll get a little insight to some other aspects of your engine. Well worth the $28, imo.

@iamdub is right on with the crossover hoses.

Otherwise, I stand by my "let it idle" method. You will find it eventually, even if it's got to get worse first.

 

[Chubbs]

here’s what i’m talking about.

this is supposed to be dex cool. zerex has a bottle, when you google it, actually says “DEX COOL” where this 1 has ‘american vehicle’

it was throwing me off. i compared the industry/engine spec codes and they all match up. so, zerex took the name dex cool off of their dex-cool antifreeze. at least where they sell it down here. i searched google and could not find a picture where ‘dex cool’ is removed from the label

 

[wjburken]

here’s what i’m talking about.

View attachment 238412

this is supposed to be dex cool. zerex has a bottle, when you google it, actually says “DEX COOL” where this 1 has ‘american vehicle’

it was throwing me off. i compared the industry/engine spec codes and they all match up. so, zerex took the name dex cool off of their dex-cool antifreeze. at least where they sell it down here. i searched google and could not find a picture where ‘dex cool’ is removed from the label

I would imagine it is fine as they it is for GM vehicles.

On a side note, I would save that jug when it’s empty and then next time by the concentrated coolant and mix it with your own water in that jug. The jug cost about the same but your not paying for water. Some folks say use distilled water. I use tap water and have never had an issue myself, but either way, you will save money.

 

[retiredsparky]

If you have rear heat, the most common leaks on older tahoes, yukons, etc are at the heater hose tee connections at the fire wall above the engine. O-rings are the way that the factory seals these connections. O-rings should not be considered a permanent connection as they shrink over time and will result in leaks, whether coolant, fuel, freon or transmission fluid. Replace all of the parts, including the tees themselves, if it is leaking.

On another note, auto parts stores have kits that contain ultraviolet die and a small ultraviolet flashlight for detecting coolant and other types of leaks. The kits work very well and are relatively cheap.
Larry