Jimmy2x

Have a 87 5.7 TPI Iroc that keeps losing antifreeze. The PO rebuilt the engine (supposedly) about 9k miles ago. When I got the car I changed all the fluids including radiator and engine block flush. Seemed normal to me to add some fluid to the jug now and then assuming some air was working its way out but that was now 5K miles ago. Shouldn't take that long to stabilize!

Currently the car runs well with no white smoke at startup. The oil also looks great and the level is not changing. It's always bone dry under the car and there is no sign of antifreeze anywhere in the engine compartment. I've only pulled a few plugs just for grins and they all look good also. I am assuming the antifreeze is going out the tailpipe but how do I determine if it is a head gasket or intake gasket. Is there a way to test each seperately? Thanks.

Tibo

iTrader: (15)

If it's an intake gasket than the most likely place for coolant to go is in the lifter valley area where it would mix with the oil and you would see the coolant turn a milky color from a hint of brown (not much coolant) to what looks like coffee with a bunch of creamer (lots of coolant). Upon draining it's also possible for the water and oil to separate out like salad dressing and you could drain the oil and then the water on top of the oil. If it is a head gasket leak the most logical place for it to go is the combustion chamber. It would just be burned off there. If he rebuilt it and it is leaking into the chamber it could be a warped head or engine block, incorrectly installed head gasket or another bad head gasket.

Jimmy2x

Thanks Tibo. I'm pretty sure that I know what has to happen.....I gotta tear it all down and find out what I'm dealing with. I just had a small glimmer of hope that maybe there was a way to definitively say it's just an intake gasket. I guess this winter will include some exploratory surgery.

Tibo

iTrader: (15)

You can do a leak down test on the cylinders to avoid pulling off both heads.

sofakingdom

iTrader: (1)

More likely the water pump.

Head gaskets hardly ever go bad that way. If they're bad, you'll have one or more dead holes, 99% of the time. No dead holes, no gasket failure.

Could be head bolts though... might have to pull them 1 at a time and re-seal them.

Jimmy2x

Wouldn't the water pump leave some sign of leaking someplace? I've only ever seen them leak out the weep hole or the pulley shaft itself.

I would certainly believe one or more of the head bolts having an issue. I guess the best place to start would be with the leak down check and hope that I don't have to actually pull the head(s). Any other ideas???? Thanks for the help fellas.

Drew

iTrader: (58)

Boom!

Had a coolant consumption problem for a few years, wasn't too concerned since no other symptoms. A couple weeks ago I was under the car for unrelated reasons and noticed the waterpump has clearly been pissing from the weep hole for a while now. Also explains the gunk on the back of the waterpump pulley. No drips since it would sling the leaking fluid off the pulley when the engine was running.

Jimmy2x

I drove the car to work today so when I get home I will leave it running and go over that water pump with a fine tooth comb. God, I hope you guys are right! Thanks again.

Stevolwevol

iTrader: (1)

If you pulled the plugs and they all look good, then it's probably not a head gasket, or a cracked head. You would have a clean, pristine looking plug from "wash" from the antifreeze. How does the temp gauge read? Does it fluctuate? An intake gasket could leak, but it may dry before it drips. Do you smell antifreeze after the engine is warm?

Jimmy2x

Temp gauge reads very consistently around 180-185. Checked the water pump all over last night and everything was bone dry. This was after a 26 mile drive. I do smell antifreeze when the engine is warm but the cap on my reservoir tank is an open vent type. But, even with the hood closed you can smell the antifreeze when you shut it off.

sofakingdom

iTrader: (1)

The wp leaks from the "weep" (actually, bearing vent) hole behind the pulley.

When it leaks the coolant gets slung everywhere by the pulley when running, but runs down the back bottom of the lower rad hose while off.

Get up under the front of the car and look at the bottom of that hose.

Jimmy2x

When I got home from work last night I parked the car with the front end hanging over the edge of the sidewalk then crawled under it. Everything was bone dry. Hose, weep hole, inside the water pump pulley...everything. I started the car and made sure it was good and warm after running for few a minutes and looked at everything again with a good light while it was still running. Again...nothing, everything dry.

I may just run the car for the next two months until I put it up for winter and see what develops. I would think that something would begin to be more obvious as time goes on. I'm beginning to think I'm losing my mind.

GeneralDisorder

iTrader: (1)

Also the rear coolant passages to the intake manifold. The manifold will get pitted up and they become very hard to seal. The coolant leak is hard to spot on the back side of the engine and often dries before it makes it to the floor. I had to bead blast my lower manifold and the fill the pitting with metal filler and block sand it to get a proper seal.

Jimmy2x

I had not heard of that one before but that is very believable. Would make sense that the antifreeze smell could be from it drying on the hot backside of the motor. Next time I drive it I will have to get my head and a good light in on the back of that manifold. Thank you for the idea.

84 Z-28 350

I've had a heater core slow seep cause antifreeze loss, didn't figure it out until it eventually got worse, I changed the heater core and my slow leak prob went away

mikeceli

iTrader: (2)

How about testing the cooling system for "Products of combustion"? You can buy a dye-test kit for approx. 50 bucks, or find a TRUSTED shop to conduct the test.

Was there a dry stain coming f/ the pump weep hole?

GeneralDisorder

iTrader: (1)

This will generally be evident as an oily black ring of goo inside the overflow bottle.

The chemical tests don't work well. The best way is to use an exhaust gas analyzer.

But if there's no oily ring, or loss of compression, then this is highly unlikely to be a HG problem. My vote is still lower intake manifold coolant passages at the back of the heads.

GD

Stevolwevol

iTrader: (1)

I replaced my intake gasket cause it was leaking, but it was in the front. It took awhile to notice. At first I saw nothing cause of evaporation, but as the gasket leaked more, I could visibly see a small pool of green, but it wasn't dripping on the ground. If your car has the original gasket then this may be the case.

NoEmissions84TA

iTrader: (1)

There are coolant pressure testers that you can buy or maybe rent.

Or you could even use the DIY method.

GeneralDisorder

iTrader: (1)

Valve stem in the radiator cap. Nice. I would suggest a bicycle pump. If you use a compressor it would be very easy to go over 15 psi and blow the radiator tank or hoses out.

GD

NoEmissions84TA

iTrader: (1)

True. Another concern is if you have a blown head gasket leaking into a cylinder.
You have the potential to hydro-lock the engine and bend a connecting rod if cranked.

GeneralDisorder

iTrader: (1)

I haven't encountered the starter motor with a sac big enough to actually bend a connecting rod just from cranking. Not saying it isn't possible but the only bent rods from hydro lock I've seen were running engines that ingested large amounts of water. I've hydro locked a few motors with gasoline from stuck injectors, etc and in those cases the engine survived or at least didn't bend a rod. Wiped out a rod bearing on one of them.

GD

sofakingdom

iTrader: (1)

Head gaskets are almost NEVER responsible for mystery coolant loss, in this type of engine.



Here's what one looks like, with the holes marked. Sorry the photo is so big, I didn't realize that until after I posted it. Copy it and paste it into Paint or something to see the whole thing.

Cyan is the "steam holes" for a 400, which your gasket doesn't have. Red is the dowel pin holes. Yellow is the bolt holes. Light grey is oil drainback from the rocker arms. All others are coolant. The magenta ones are the most important... they cool the hottest bit of casting in the whole engine, which is, the part of the head between the 2 center exhaust ports... that was what I originally posted this photo to explain to somebody.

Now, LOOK AT the various spacings of things in that gasket, and consider the pressures. Coolant is under 15 psi or so; combustion is in the 1200 - 1500 kind of range. THIMK: if that gasket is going to fail, WHERE is it most likely to do so? Would it not be where 2 1500 psi chambers (aka "cylinders") are right next to each other with only a very narrow strip of material separating them?

This is why, when a gasket fails, it ALMOST ALWAYS affects the way the engine runs. They fail between cylinders, the thin places in those cyan rectangles with the steam holes, and VERY RARELY anywhere else.

Put head gasket failure out of your mind.

Bolts are a different matter... on every single one of them, all 17 per side, the threads are exposed to coolant. If the builder used an inappropriate sealer such as RTV on them, or no sealer at all, then they are VIRTUALLY 100% IRONCLAD GUARANTEED to leak. Which is why I suggested pulling every one, one at a time, and putting some thread sealer (my preferred stuff is the "high temp automotive thread sealer with Teflon" from Permatex or Loctite, same company, whichever brand the label says) on their threads and under their head, and re-torqueing them to 60 - 62 ft-lbs. DO NOT use a "clicker" type wrench. Use a beam or dial type. MAKE SURE you measure the torque while the bolts are actually turning, i.e. DO NOT make the mistake of setting them by their "breakaway" torque. ABSOLUTELY NO MORE THAN 65 ft-lbs: if the torque exceeds that while the bolt is moving, back it out, put more sealer on it, re-torque.

I like that valve stem in a rad cap... so simple and basic and cheeeeeeeep, yet perfectly functional. However a leak typically has to be pretty yuuuuuujjjjjjje to be detectable that way.

The intake gasket is a very good suggestion also. Depending on what kind was used, they can easily fail. The cheeeeep paper-ish ones are total crap and are almost certain to fail rapidly. It will be obvious if they have failed, when you pop the intake off.

If it was mine, I'd pull the intake and exh manifolds, and the valve covers; do the bolts; and make sure the intake goes back on PERFECT. I'll be happy to detail how to do that in a separate post when you get to that point.

Drew

iTrader: (58)

Umm, no. You're not going to smell antifreeze from the vent in the reservoir cap. But you would smell antifreeze inside the car, from a leaking heater core.

If you can smell antifreeze, you should be able to see that antifreeze. Good bright flashlight and look around thoroughly the next time you smell antifreeze. Rub your hand over the carpet under the passenger's side of the dash, too.

84 Z-28 350

The smelling antifreeze thing makes me vote for the heater core too

Jimmy2x

Thank you for all the ideas fellas. Although I do smell antifreeze when I shut off the vehicle, it is not on the inside of the car, and it is not really strong.

I have checked the carpet and up under the dash on the passenger side and everything is dry. Any other places that heater could be leaking?

Not knowing what the PO did to the head bolts during the rebuild that seems to be a good place to poke around. But, if those bolts have worked their way loose, where would the antifreeze be going?

Sofakingdom I appreciate the support (and free education) and may be sending you a PM when I tear into the car this winter.

Stevolwevol

iTrader: (1)

Is you windshield getting fogged up? A leaky heater core will do this early on before your it starts dripping on the carpet.

Jimmy2x

Not that I have noticed. 56 degrees this morning on the way to work so temps should have been ideal with that cool windshield.

tater

iTrader: (10)

I suspect the heater core also. Just to rule it out without changing it, loop the two heater hoses to bypass the heater core. Basically, remove the hoses from the heater core and put them together, end to end. Will have to buy an adapter for about $5 at a parts store because they are two different size hoses.

If the problem goes away, the heater core is bad. It's a frustrating "process of elimination".

Make sure to post your results. Many don't.....

Jimmy2x

Nice idea Tater. That would eliminate one possible suspect. Cheap and easy too! thank you.

TylerSteez

iTrader: (3)

Wondering if the previous owner used thread sealant on the head bolts when rebuilding the engine.

NoEmissions84TA

iTrader: (1)

Be EXTREMELY careful when removing those hoses. If you pull and twist too hard, then YOU WILL be replacing the heater core.

Stevolwevol

iTrader: (1)

If the heater core is leaking, you will smell antifreeze inside the car, and you WILL get fog on the inside of your windshield. Is the smell strong inside the car, or under the hood???

Jimmy2x

Smell is only under the hood. Don't think its the heater core. Temps were in the low 80's today on my way home and I stuck my nose up under the dash and all over the carpet. Even pulled up the carpet to smell and look at the pad. No smell, no moisture. Pretty sure it's not the heater core.

Various individuals have suggested that there was no sealer or poor sealer used on the head bolts during reassembly. Assuming this is the case, where would the antifreeze be going?

84 Z-28 350

It would ooze out of the heads of the bolts, and probably evaporate before it would be noticed...I had a similar problem...the ones to really worrie about are the ones under the valve covers, they will turn to sluge in nothing flat and you'll never notice it in the pan, if it's leaking from the ones under the exauast manifold/headers it won't hurt anything but it is a pain in the *** to get at

Stevolwevol

iTrader: (1)

When the engine gets warm the antifreeze will evaporate before it hits the ground, if it's leaking in small amounts. On my earlier post I explained about my intake leaking in the front, and I could see a very small amount of green pooling up, but it evaporated before it dripped. If your intake is leaking toward the back of the engine, you wouldn't be able to see it. You would smell it though.

If this is your original intake gasket, it stands to reason yours could be leaking. It's not catastrophic engine failure, and it can be fixed with a little elbow grease. It is of course necessary to rule out other leaks before replacing anything.

Tootie Pang

iTrader: (2)

How often and how much does it need when it needs a coolant refill?

Jimmy2x

I started keeping track of level and mileage when I originally started this thread. I have put about 300 miles on the car and this morning with the engine cold it was down about 1/4 to 3/8 of an inch in the overflow jug. I haven't been adding any until it was at least an inch below the full cold line but like I said I wasn't watching my mileage before.

84 Z-28 350

That's a small leak..that will be hard to find

Tootie Pang

iTrader: (2)

Agreed.

JA411

Pick up some fluorescent coolant dye GM part #12378563 or after market. Pour about 1/2 the bottle into radiator. drive or aleast get thermostat to open, use black lamp and the dye will glow green. I use it all the time at work and at home.
Joe

84 Z-28 350

I need to do that to my wife's Chevy Tahoe lol

sofakingdom

iTrader: (1)

If yer Hoe has a 5.3 with 706 casting heads, it's probably this.



All of the truck boards are full of the same complaint; Castech 706 heads that crack right above the head bolts. It's an epidemic. Chevrolet refuses to acknowledge the existence of the problem, let alone accept responsibility / accountability for it. What a bunch of weeeeeezelz.

The one in the photo is a 2004 Avalanche with a LM7.

If your Hoe puffs a GIANT blast of oil smoke when it starts up in addition to the slow coolant loss, and the oil pressure seems to go away REAL QUICK after an oil change, suspect the head crack.

sofakingdom

iTrader: (1)

I forgot: Steve, 9 head bolts are inside the crankcase (7 long, 2 medium), therefore those leak into the oil; and 8 (all short), all in a nice row right under the exhaust manifold, communicate with the outside world.

84 Z-28 350

I already changed out the heads they were the castech casting.....it's dripping off the harmonic balancer but other than the drips and water loss there's no evidence of the sorce....I'm thinking the water pump, but I want to be sure before I change it

sofakingdom

iTrader: (1)

Probably not the WP, but could be of course.

The WP and TC gaskets for the water passages are equally notorious for leaking. Although to be honest, if I took off the WP to change the gaskets, then that must mean it's been on there for AHELLUVA LONG time; I wouldn't put it back in that case, even if it was "good", I'd refresh it. Similarly if I took off the TC I'd put a 10296 oil pump and a new pickup tube O-ring in it. Oh wait... I already did just exactly that.

84 Z-28 350

This will be my first time diving into the front of a ls engine, the heads were a PITA, hopefully the front is eaiser, I guess I'll find out when I get back to the US in oct/nov

Jimmy2x

Quick update. I'm slowly finding time to tear into the motor. Last night I drained all the antifreeze out of the radiator and block. It all looks very good, including the overflow tank. No oily film or discoloration at all. Clean and green!

I also performed a compression test with the following results
1 - 160
2 - 170
3 - 180
4 - 155
5 - 155
6 - 165
7 - 145
8 - 155

Right now I have all the plugs out of it and everything removed from the top and the front of the engine but intake manifold and valve covers are still in place. My next plan is to remove the manifold and valve covers and see if there is anything suspicious.

I will try to keep the group posted on my progress. The most useful posts are the ones where folks share their solutions.

GeneralDisorder

iTrader: (1)

Those numbers are kinda low and all over the place, but not the numbers you would see from a HG failure.

But 20% difference across the board is pretty poor overall results. For comparison, my 160k mile original 1986 LB9 is between 185 and 195 on every cylinder. That's after sitting for 11 years outside in the elements. Of course the cooling system looked like pond water and I had the aforementioned intake manifold gasket and mating surface pitting issues. After dealing with that and quite a few system flushes it's more or less a greenish color and doesn't seem to use a significant amount of coolant. No matter really - when the Dart 400 block goes in the rusty cooling jackets will vanish.

20% is kindof a no-mans-land - you might get a few ten's of thousands more out of it, but it's definitely borderline rebuild territory. Rings and a valve job at the least if the cylinders look good.

GD

Jimmy2x

No man's land is right. I am just going by the PO's statements and really have no idea what I'm dealing with internally. He said the motor was punched 40 over with new rings and some head work blended to a 3-angle valve job but as I continue to explore the ice keeps getting thinner under me. The engine supposedly only has about 9k on it since it was rebuilt.

I'm seriously just thinking about putting the damn thing back together and driving it until something catastropic happens. That way I'll at least know what I have at that point. I don't have have the skill set, time, or money to do piston rings and a valve job.

Maybe I should just stick with my air cooled Harley. A lot less crap to go wrong on that!