Tracking Down Hard-to-Find Dexcool Leak on 5.7 Chevy Engine

[jjrbus]

I have a leak in my 01 5.7 cooling system. I have no coolant in oil, transmission fluid. There is no white smoke. I have done combustion leak test and pressure test. Combustion test is negative, pressure test verify leak. Yes I know the coolant is orange and should be easy to find, I cannot find it.

I cannot find, the other ACD tracer is for oil.

ACDELCO 10-5046 DYE COOLANT SYSTEM​

And others do not appear to be compatible with Dex cool. Anyone know of any others that might work.

 

[booster]

Very possible it is only leaking when it gets hot, usually because of a bad intake gasket or headgasket into the combustion chamber. Head cracks can do that also but are less common. Once warm it can be much harder to see the vapor in the exhaust, but you might be able to smell it. The intake gaskets can leak on top of the transmission and be very hard to spot and the rear of the intake is a common failure point, especially with Dexcool and the earlier engines.

 

[mik mikgil@icloud.com]

I had the same problem.Showed up on oil analysis from Blackstone. It was a very small amount with no external leakage. Intake manifold gasket had deteriorated in the corner and was leaking very small amount inside. Try an oil analysis to see if there is trace amounts of antifreeze in oil. It was not visible on dipstick. In the mean time, retorque your intake manifold bolts. Don't wait. If there is coolant in oil, it can/will wipeout your bearings. Contact Blackstone for free pre mailer sample containers.

 

[Hatteras Jim]

Assuming this is a chevy 5.7, the problem is probably an intake manifold gasket. They are famous for this gasket leaking due to a problem with the original gasket. The leak is usually on the very rear of the engine block and may manifest itself only when running; with evaporation making it hard to spot the leak. The leak can be internal or external; but, you had the internal parts checked. I had 2 different 5.7s (both '99s) and I needed to replace the gasket in both of them. Both of them were leaking (more of a seep) externally on the driver's side in the very rear which is buried under things and hard to locate. Get it up to running temp and observe while someone revs it up. It's at the seam where the upper manifold joins the block. If that part of your engine is dirty, you may need to degrease it first to see it. Not a bad job if you want a challenge and have the place to tear it down and work on it. Estimates for me (4 years ago) were $800- $1000 dollars. Some good videos on the tube. Good luck

 

[jjrbus]

This leak has been a bit frustrating, no coolant stains, no signs of leaking. I rented a coolant system pressure tester again and yesterday found what looked like water seeping. Checked it again today and see it slowly dripping. Still not sure where it is coming from? Passenger side. Trying to post a video and not working for me, will keep trying. Cannot figure video out.

 

[booster]

Is that the water pump to block flange you are pointing at? If so, several of the bolts go through to the water jacket of the block and are prone to leaking after a while, depending on if and what sealer was used on them. It could also be a leaky head gasket in that area.

 

[youngnretired]

I was first thinking this was a 6.0L, but it's an older chassis with the 350 engine. The 6.0L engine has a freeze plug on the end of the head, but 350's don't (at least the late 70's and earlier vintage). Also, all the bolt holes on the end of a 350 head (again, late 70's and earlier) are blind holes, so nothing goes into the water jacket on the end. 2001 vintage?? I have no working experience with 350's this new.

On a 350, the lower row of head bolts and (I believe) the two end bolts on both ends of the head holding it down to the block underneath the valve cover goes into the water jacket. If any head bolts were leaking, it may only be a matter of time before it corrodes enough and starts to get into the cylinders, and then it may be a much larger job to fix with potentially catastrophic results.

Also, on the late 70's and older stuff, there's a couple fittings on the intake that go into the water jacket (for things like heater hoses etc), and then the thermostat housing is on the front and top of the intake. These are also leak point possibilities.

As booster said, this could be a leaking head gasket, head bolt, the end of the intake manifold bolt/gasket or leaking from a fitting above this area and wicking down to where you can see it. Unfortunately, you're probably going to have to take off the serpentine belt system at a minimum to get a good look at that area to see where the water may be starting from.

 

[jjrbus]

Is that the water pump to block flange you are pointing at? If so, several of the bolts go through to the water jacket of the block and are prone to leaking after a while, depending on if and what sealer was used on them. It could also be a leaky head gasket in that area.

Video would have been better, it is not the water pump it is where the belt tensioner is mounted. GM says it is this bracket. Not sure where the water is coming from, this is where I see it dripping. Site Maintenance

 

[jjrbus]

I was first thinking this was a 6.0L, but it's an older chassis with the 350 engine. The 6.0L engine has a freeze plug on the end of the head, but 350's don't (at least the late 70's and earlier vintage). Also, all the bolt holes on the end of a 350 head (again, late 70's and earlier) are blind holes, so nothing goes into the water jacket on the end. 2001 vintage?? I have no working experience with 350's this new.

On a 350, the lower row of head bolts and (I believe) the two end bolts on both ends of the head holding it down to the block underneath the valve cover goes into the water jacket. If any head bolts were leaking, it may only be a matter of time before it corrodes enough and starts to get into the cylinders, and then it may be a much larger job to fix with potentially catastrophic results.

Also, on the late 70's and older stuff, there's a couple fittings on the intake that go into the water jacket (for things like heater hoses etc), and then the thermostat housing is on the front and top of the intake. These are also leak point possibilities.

As booster said, this could be a leaking head gasket, head bolt, the end of the intake manifold bolt/gasket or leaking from a fitting above this area and wicking down to where you can see it. Unfortunately, you're probably going to have to take off the serpentine belt system at a minimum to get a good look at that area to see where the water may be starting from.

Too much in the way to get a good look, there might be a freeze plug in the end of the head. Too much in the way to see. I may stop by a shop and ask if the want to look at it and give me an estimate. 78 now so not doing what I would have done 20 years ago.

 

[youngnretired]

A shop with a small slim cable style video camera may be able to get in there closer and give a better idea on what's going on.

 

[jjrbus]

A shop with a small slim cable style video camera may be able to get in there closer and give a better idea on what's going on.

I have a fairly good one, I should take a look.

 

[booster]

As youngnretired mentioned you need to look above that area to get to where the water is. Removing that tensioner support bracket is not a big job but time consuming sometimes. If the intake gaskets haven't been replaced with the new style ones they would be suspect but the rear leaks seem to be common than front. Head bolts usually don't leak down the front of the engine, but head gaskets can. The older Dexcool on the early engines, combined with incompatible intake gaskets caused lots of leaks. Of course the vans make anything related to the top of engine more difficult do to access issues.

 

[GroupB]

For what it's worth, I had a situation of slowly loosing coolant with no visible signs of loss. Figured it was a head gasket leaking into a combustion chamber but took no action. Much later I was doing a repair where coincidentally I cound see the underside of the water pump that was now visible with parts removed. The weep hole was surrounded by crusty deposits. The leak was apparently only at operating temperature and slow enough for the coolant to evaporate without making it to the ground. Replaced the water pump; no more leaks.

 

[jjrbus]

Removed the coolant reservoir tank and got out my bore scope, spent an hour and cannot find coolant above the drive belt tensioner bracket. Not saying there is none there I can not find any. Almost thinking it is the bottom bolt in the tensioner bracket could be the issue.

 

[youngnretired]

The bolt holes you have circled in your picture are actually at the top of the bracket. See pictures of the bracket installed. I believe the two recessed holes in the bracket are where it attaches to the engine and your picture shows the bracket upside down. It appears that the bolt on yours that's has the coolant on it is the recessed area to the right of the machined surface on your picture (where the tensioner bolts to) and I believe that that bolt goes into the lower left bolt hole in the head (from your original pic of the leak), but these bolt holes in the end of the head are blind and don't go into the water jacket. The only holes going in the front of the block and into the water jacket are the water pump bolt holes. Could it be the freeze plug below the head that's leaking, or if the right side bolt hole in the brackets when it's installed uses one of the mounting bolts for the water pump? I would think that if this bracket was attached to a water pump bolt that the bolt would have a threaded end on it and uses a nut to hold the bracket to the block instead of a bolt. Because if it was a bolt in this location, changing the bracket would also let the coolant out of the block and possibly loosen things up enough that would require the water pump to come off as well. See pics

 

[jjrbus]

The bolt holes you have circled in your picture are actually at the top of the bracket. See pictures of the bracket installed. I believe the two recessed holes in the bracket are where it attaches to the engine and your picture shows the bracket upside down. It appears that the bolt on yours that's has the coolant on it is the recessed area to the right of the machined surface on your picture (where the tensioner bolts to) and I believe that that bolt goes into the lower left bolt hole in the head (from your original pic of the leak), but these bolt holes in the end of the head are blind and don't go into the water jacket. The only holes going in the front of the block and into the water jacket are the water pump bolt holes. Could it be the freeze plug below the head that's leaking, or if the right side bolt hole in the brackets when it's installed uses one of the mounting bolts for the water pump? I would think that if this bracket was attached to a water pump bolt that the bolt would have a threaded end on it and uses a nut to hold the bracket to the block instead of a bolt. Because if it was a bolt in this location, changing the bracket would also let the coolant out of the block and possibly loosen things up enough that would require the water pump to come off as well. See picsView attachment 2418107View attachment 2418108

Thanks for the pictures, much appreciated. I looked again this morning the freeze plug does not seem to be leaking. I cannot tell for sure but suspect it is the head gasket. I was hoping for something simple that I could repair myself. At this point I am better off taking it to a shop and let the pros look it over. Hopefully the new shop I found will want to work on it.

 

[jjrbus]

Finally got my RT in for the control arm mod and asked them to check for the coolant leak for me. He told me he sees the leak and suspects a freeze plug but it is behind the power steering pump and cannot see the source. We are chatting about it and he says power steering pump again and I say you mean alternator. No it is on the driver side behind the PS pump!

Van is sitting on his level alignment machine, in my yard it must be sitting on an angle and coolant running to passenger side and showing up behind alternator! He does not want the repair job so back to renting the cooling system tester and checking again.