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Chevy Suburban 5.3L coolant leak into engine

I'm having a difficult time solving an internal leak of antifreeze into the top of the engine. It is getting into the valve train and apparently into the cylinders as well, but never gets into the oil pan. It uses about 1 gallon a week with no external leaks. Oil fill and PCV cover inlets are full of white/brown mix of water and oil. I've already changed the head gaskets once, about 6 months ago- they were leaking. Milled the heads flat, etc. Thought the problem was fixed but it came back in about 2 months. Any ideas?


  • arriearrie Posts: 312
    Hi daves67,

    It sounds like changing head gaskets fixed the problem for two months but the problem then came back, right?

    Have you re-torqued your head mounting bolts after gasket change?

  • daves67daves67 Posts: 2
    Hi Arrie,
    No, never did that. We did end up having the radiator rodded out, it was clogged with the GM coolant - the engine got up around 240 deg. before we had it fixed. Of course it happened after the new gaskets. I'm afraid that with 140K now on the motor, it may be best to just go through it, but there is no sign of water in the bottom end and the oil pressure is still around 45 lbs. Will the stretch bolts handle a retorque?
  • arriearrie Posts: 312
    Hi daves67,

    I'm not sure what you mean by 'stretch bolt' but what ever the bolt is it will handle the re-torquing. Re-torquing is sometimes needed for head bolts because the new gasket settles a little bit. This used to be a normal procedure and I'm quite sure it still is for some car engines. Re-torquing the head bolts simply means tightening them back to the torque they were set to when the head gaskets were changed. This does not increase bolt stress.

  • tivytivy Posts: 2
    I had the exact same thing happen. I put in a bottle of Bar’s leak, which I think comes installed form the factory, and 50,000 miles later all is still well. I now think I could have done that in the first place and never changed the head gaskets.
  • I am the parts department manager for a new car dealer in Virginia. Recently we had a 99 Sliverado with the same problem. It had the 4.8 liter motor, but is basically the same as the 5.3. There is an issue with some of these motors, cracks develop in the head underneath the valve cover and coolant runs out of these cracks and down the oil drain ports in the head, straight down to the oil pan. GM is doing nothing about this. The best fix is a new wngine, which is what we did. New heads are around $1100 each, and a new motor costs around $3000 (new Goodwrench motor). Alldata has more info on this if you have access. You can remove the valve covers and see where the coolant is running down the bottom of the head to the drains, it is clean there. If you pressurize the cooling system with the valve covers off, you may even be able to see it leaking. Sorry for the bad news:-(
  • 2001 Chevy Suburban with 5.3 with close to 100,000 miles that is loosing coolant and can not find leak. Is anyone else having or had this problem. It's not loosing a whole lot but it is. There is no water in the oil.
  • kiawahkiawah Posts: 3,666
    Well if it is leaving, it is either leaking on the ground, or into the passenger compartment (as in a heater core leak), or into the engine oil, or into the intake manifold. Into the intake manifold would then be spit out the exhaust and typically you notice it with white smoke (moisture) after the car has warmed up. The real concern is that you can ruin your cat converter, which is a costly problem.
  • 350 engine what about the plastic intake? any one have any input on that
  • hi i don't want to offend anyone but Bars leak will do nothing but cause you more problems in the will plug thermostat,heater core,radiator,water jackets and so on...
  • my tahoe needs coolant about ever 3 months about half gallon.i can smell the coolant but see no leak. and have a grinding sound while driven i think it's the transfer case. what should i do to help these problems?
  • kiawahkiawah Posts: 3,666
    A garage that handles radiators and a/c can easily troubleshoot your coolant problem. Could be a leaky hose connector, leaking water pump, radiator leaking, heater core leaking (a 2nd if you have the rear heater), leaky overflow tank, one of many hoses leaking, or a leaky head gasket where the coolant is leaking into the engine. They'll pressurize your system, and check for where the leaks are. You should get this diagnosed, as if the problem is that it is leaking into your engine, you could ruin your engine or catalytic converter......big bucks.

    Head to a transmission shop to hear and diagnose your grinding noise. Depending upon what this problem is, may not be cheap to fix, but it could prevent a more catastrophic and expensive problem.
  • I have the same issue with my 2004 suburban I was told the 5.3 came through with heads that were poorly casted and they developed cracks around 100,000 mi. Sure enough mine started drinking antifreeze at about 105,000 I was told the best remedy is that spending 3000 dollars on a new motor makes more sense than 2,400 on new heads for an old motor. That said, I bought two bottles of " steel seal " for 85 dollars to see how much more I can get out if this motor. I'm at 119,000 Miles and counting , not using any antifreeze and the tailpipe is dry ( knocking on wood right now ). One thing I did is un-hook the heater hoses so as not to plug the heater cores when I ran the sealant through the motor.
  • I had this exact problem on an '03 Suburban. It cost me ~$2300 to replace the 2 heads at 88K miles. In hind site a complete enginer replacement may have been the way to go, although I expect that the labor costs would have been much higher. GM customer service was useless. It is difficult to understand how a know design/manufacturing defect is not a recall issue. That is the last GM product I'll ever own.
  • maryt13maryt13 Posts: 1
    My 2003 Tahoe Z71 with about 116K miles now, has had a coolant leak for the last few years.
    I've considered taking off the skid plate to try to visualize the source, as there's a small puddle - maybe an ounce of fluid - on the driveway or garage floor some hours after driving. I had it checked at a trusted garage, and the owner said that when pressurized (from driving) coolant can 'weep' from around the head gasket. He couldn't find anything. Its not getting in the oil and so far its only a mild nuisance. I just keep a bottle of coolant in the car when on long trips, and refill as needed every month or so. I can't afford major repairs, so for the cost of a couple gallons of antifreeze a year, I'll just keep on trucking.
  • I am reading these posts with great interest. I have a 2002 Suburban. It has 181,000 miles and has never been a problem - until now. It just started leaking coolant two weeks ago. I took it to my trusted mechanic, who advised me to buy a new car within the year. He also has a Suburban which is a 2001, and it is leaking coolant. He took the engine apart on his - used ultra-violet lights - couldn't find the leak. He said that it is likely an internal leak, and that it often goes into the oil reservoir, which then creates sludge and will eventually ruin the engine. I agree that if this is a common problem with these cars, there should be a recall and a manufacturer's fix.
  • Chevy's are plagued with this problem-- usually the intake gasket leaking at right rear of engine where the water jacket is- is a poor gasket design. A gallon a week would either go out the exhaust or leak to the ground. But I am confused-- it gets into the valve train but not the oil pan? The muddy mix may be whats fooling you--- can be from condensate (antifreeze leaking into engine) but your oil should be milky as well. I had the same problem on a 96 Suburban and the gasket repair was the solution if that helps.
  • rbdogrbdog Posts: 1
    Hi There,

    That's exactly what's happening to my truck, word by word as you described. Took it to a mechanic and he said it's the water pump, however I doubt it. I think it may be a leaky gasket or something. If you find out what's actually causing it please let me know. One of these days when I have enough time I'll try to take the front apart and maybe find out where it's coming from. Good luck!! :)
  • Hi,

    I have a 2005 LT suburban that had me baffled for about its coolant leak. It was dripping around the transmission (the pink color had me thinking it was transmission fluid first), leaving a decent size puddle. I feared it was the intake gasket but the oil was clean and all parts of the front and side of the engine were clean and dry... just about to give up and ready to pay big money on a repair when i finally found the leak! There are 2 long hoses that connect to the heater core on the passenger side of the truck. There is a white plastic "T" connect to the fire wall and the o-ring seal on it was bad. The white plastic piece was fine, just the internal seal had failed and its right below it is the A/C drip pan. This was the reason the coolant was traveling all the way back to the transmission housing. You can't just buy the o-ring seal, i had to buy the entire "T" but it was only $35 and the job was not too diffucult. I was really glad not to have gone into the heads or water pump route to resolve this. Hope this helps others with the similar odd coolant leaks with out a clear source issue.
  • Thanks for the encouraging suggestion, my 2003 Z71 has had a slight coolant leak for a few years, a little puddle on the floor after it has been parked for a while, or a trail of drops leading out the driveway. Within the week it has been losing a lot more coolant, so I took off the covers above and below the radiator and inspecting everything, can't find any sign of leak. Oil looks clean. Loosened the skid plate (removed front 2 bolts, loosened rear ones) but there doesn't appear to be any fluid accumulation there. Do you have a part number for the T connect?
  • Has anyone contacted GM about this problem. I have and I got the run around. I argue that theirBulletin #06-06-01-019b says that they know and rreconize the problem with castech heads, and that durning casting of this heads that they have porosity in very specific areas. They want to argue that mileage is the issue, but I argue that porosity happens durning the molding process and NO matter how much you drive or run the motor that they dont get porosity or gain more porosity. They are not wanting to except responisblitiy for the bad metal and hold the castech company responible for faulty product. They want me to take to a gm dealer and have them to check the heads for porosity, Just to remove heads is $800. Then I have to pay for the mag test also. Has anyone looked into a class action Lawsuit about this problem and does anyone think it would be worth it.
  • You may want to check your heads to see if they are casteck heads. There is a document out there # 06-06-01-019b put out to gm mechanics to let them know about bad castings of these heads. they have porosity in the metal whick is leaking thru to the lifter area but evaporating because of heat leaving a sludge mix oil.
  • I have a 2004 Tahoe LT with the 5.3 flex fuel engine, that I bought new. I have the very same problem that you have described. At about 40,000 miles, I noticed that coolant was always being added when I had the oil changed at a 'quick lube' shop. This got worse by 80,000 miles. The dealer did a pressure test and found no leak or drop in the pressure. I am having to add about a pint every 200 hundred miles. The lube shop suggested a Radiator shop and they suggested to replace the coolant reservoir cap. THAT, has fixed the problem.
  • I see so many here talking about coolant leaking in the 5.3 engine, well people, the 5.3 engine is designed so no coolant can leak into it! 5.7 is different, they had serious coolant leak into engine issues, but those with 5.3 are not having issues with coolant leaking into the engine via intake because this cannot happen!
  • Please explain your comment.

    I have a 5.3 which is burning coolant. The exhaust smells of coolant and I have to add coolant daily. I don't have any coolant puddles on the ground anywhere I park. I am not a mechanic, but assume coolant must be getting into the engine somehow or it wouldn't be coming out the tailpipe as smoke.
  • When your saying the 5.3L engine is designed not to leak coolant into the engine, I am not sure what you mean about that. I have a 5.3L engine losing gradually coolant over a period of time. I am reading about the head casting problem with the 5.3L and 5.7L engines. I don't see water in my oil, but I presume its burning up. Just curious, what you what different in the design of the 5.3L engine that makes is different? thanks.
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