04 Blazer Still losing coolant?!?!?!...............

[bandit7862]

I am having a coolant problem with my 2004 Chevy Blazer 4X4. I have posted months ago about the same issue so I did what I thought would finally solve the problem and it did not. Here are my symptoms and what I have done thus far. I am losing coolant at the rate of about 1 pint a week. I have just recently replaced the intake manifold gasket in hopes of correcting the loss of coolant and the lifter tap when cold. Now after 3 weeks and about 1000 miles, the lifter tap has returned and the coolant is still being lost. I do not have any coolant or any liquid inside the Blazer, so I ruled out the heater core. I do not have any coolant leaking on the ground at all. I cannot see any coolant leaks anywhere around the engine, as I didnt see any before I changed out the intake manifold gasket either. I must still be having coolant through the engine because the lifter tap only happens after about 1000 miles of driving and when cold. As soon as it warms up, the tapping is gone. Sometimes as soon as 10-30 seconds depending on the time between the last oil change. I have no idea where this coolant is going or what to do next. I love the truck or I would be getting rid of it. I have had this coolant issue for about 1 year now. I am just changing the oil every 1000-2000 miles before the tapping gets much louder. I am thinking on dropping the oil pan to check the screen and pan for sludge build up, but that is a hard task considering I have to remove the 4X4 gear box. I would appreciate anyones suggestions on which way I should run with this problem. By the way, when I changed out the intake manifold gasket, I did not find any problems with the old gasket or any noticable leaks anywhere, so that was not my problem, however I did notice a lot of dried up coolant build up just in the coolant passages so I cleaned them all out with a wet vac. Please help!!! Thanks, Randy

[old_master]

The symptoms you're describing are classic for leaking intake gaskets. The original intake gasket is plastic with a silicone insert that does the actual sealing around the ports. Felpro makes an improved gasket that has a steel frame with a rubber insert and is far superior to the original gasket design. The Felpro part number is MS98002T. When replacing the gasket, it is extremely important to remove all traces of the old gasket, clean and oil the threads in the cylinder heads and the intake bolts, and use a torque wrench to tighten the bolts using the proper torque sequence.

If the cooling system has not had proper maintenance, the coolant ports of the intake manifold can corrode causing pitting. Slight pitting is generally not a problem and can be "leveled" using silicone sealer however, if the pits are severe enough, the manifold must be replaced.

[SantaneroX3]

what i would do since you said it had alot of old build up coolant is : do a flush and when you put the new coolant put a bottle of stop leak since you can't see the leak and for the knock or tap in the engine when you do an oil change don't use 5-30 or 10-30 oil use something like 10-40w and a quat of lucas oil. if that knock gets worsed thats not good your gonna have to get an engine hopefully that won't happen

[Ralph123]

Your engine tap at start up and coolant loss problems may not be related.
Your engine tap may be caused by a bad anti drain back valve in your oil filter allowing all the oil to drain back into your oil pan. Try using a high quality oil filter with a silicon anti drain back valve like the Pureone oil filter by Puralator.
Your coolant leak may be a head gasket. Notice any steam coming out the exhaust at start up?

[viggy58]

personally, i dont advise using coolant stop leak products. how well have you checked for leaks? i did my intake gaskets, and after about a week, a clamp loosened on a small line on top of the water pump. as a result, i have a small leak, that i just havent had time to fix. the coolant usually burns up on the engine or water pump before it hits the ground. i RARELY ever see any kind of spotting on the ground.

can you smell coolant when the engine is running? if so, is it right away, or after the truck has warmed up for a while? make sure all oil and trans coolant lines arent leaking.

[TCGrove]

I had a problem with mysterious coolant leak with my 99 Blazer a couple years ago. It turned out to be my radiator cap. The only way I found it was when the leak got bad enough it began to condense under the hood and ended up messing up the alternator. I dried out the alternator, replaced the cap, and the mystery was solved.

[Rick Norwood]

O.K. go to Autozone and borrow the Radiator Pressure Tester. It is a small hand held tire pump with a radiator cap and a pressure gauge on it. When your engine is shut off and cold, remove your radiator cap and attach the pressure tester. Pump the tire pump until the pressure gage reaches the pressure rating of the original radiator cap. Probably around 15 psi. Get a flashlight and look for leaks over, under, and around your engine. Watch the pressure gage for pressure drop. You might even get lucky and spot the intake manifold leaking this way. I have had leaks show up in the damndest places, like on the backside of the radiator where it mounts to the frame. The water pump weeper hole is another good spot. The pressure tester will help you find and/or eliminate any external leaks. If you don't find any external leaks and you notice a pressure drop, check the oil level on your dipstick to make sure you didn't fill your crankcase with anti-freeze. AutoZone will usually loan these pressure testers for free. It is well worth the effort. Please post back your results.

[bandit7862]

Everybody has some very good suggestions and idea, however I have done 99% of the items listed and to no avail. There is some minor exhaust white smoke when it first starts up, but then goes away when warm. I truly dont think there is any external leaking, but I will get that radiator pressure tester and verify. Like I have said in the past, I have replaced the water pump, radiator, thermostat and now the intake manifold gasket. There was nothing wrong with the old intake manifold gasket, but all my symptoms led to changing it. I hate changing things that really didnt need it. I believe I am somehow leaking coolant into the engine by whatever way is possible because this is why I am starting to get that lifter tapping after about 1000 miles after an oil change.
By the way, does anyone know how hard it is to remove the oil pan on this 4X4 vortec V-6? I understand I have to remove the 4X4 section to get at the oil pan. I want to check for sludge build up on the screen and inside the pan. I know it has some build up because when I change the oil, the very last few drops of oil are not really drops, more like liquid mud. Thanks for all your help, Randy

[saturntech]

Sounds like head gaskets or warped head to me.

[Rick Norwood]

Originally Posted by saturntech

Sounds like head gaskets or warped head to me.

That is a distinct possibility. Usually a blown head gasket will cause a ton of steam to come out of the exhaust pipe. But if it is just starting to go, you could be right.