Our Community is 940,000 Strong. Join Us.


Coolant mysteriously dissapearing...


nosefirst
07-23-2005, 04:38 PM
In my '98 5.7 the coolant has been very slowly dissapearing. I can't for the life of me find a leak. I'm wondering if it might be burning it? Wouldn't I see exaust bubles in the radiator if it was?

no_h20
07-23-2005, 06:37 PM
In my '98 5.7 the coolant has been very slowly dissapearing. I can't for the life of me find a leak. I'm wondering if it might be burning it? Wouldn't I see exaust bubles in the radiator if it was?
Most likely you are leaking out of the intake gasket(s). It will only leak under pressure. You will lose coolant until the level is low and no longer able to create pressure. (At least I think that is how it works, someone may counterdict me??) This was happening to me, and sounds like most people with the 5.7 liter engine. I just got mine replaced on Fri. It's about 550-600 bucks for someone to do it.

suburban_lee
07-25-2005, 09:57 AM
I second the intake gasket idea. I had the same problem on my 99 5.7L. I might have been using about a quart every couple of months, but no leaks. While tracking down another problem, we chnaged the gaskets and there were leaks at the ends of both sides, as well as a small leak into one of the cylinders.

Haven't lost any coolant since.

nosefirst
07-25-2005, 11:53 AM
Thanks Lee,

That's what I need to hear. I'm sure at 103k mine is due.

You must have had yours heads off to find that small leak into the cylindar right?

Damm...I might as well do them too. Or do I have to anyway?

I'm getting some Barrs Leak today, and figuring on doing the rest before winter.

suburban_lee
07-26-2005, 09:34 AM
Thanks Lee,

That's what I need to hear. I'm sure at 103k mine is due.

You must have had yours heads off to find that small leak into the cylindar right?

Damm...I might as well do them too. Or do I have to anyway?

I'm getting some Barrs Leak today, and figuring on doing the rest before winter.

Not the heads, just the intake manifold. The leaks were apparent in the gaskets.

By the way, since your going to have it out, you might consider getting the whole gasket kit and replacing the upper plenum gasket, fuel meter body, etc. Be careful pulling out the injector poppet valves as they might be a little brittle.

nosefirst
07-26-2005, 11:57 AM
Good idea!

I read that GM and only GM has a gasket now thats made to remedy this problem.

Did you get your kit from GM?

suburban_lee
07-26-2005, 01:43 PM
Good idea!

I read that GM and only GM has a gasket now thats made to remedy this problem.

Did you get your kit from GM?

Nope, I used a Fel-Pro gasket kit - If I recall, somewhere around $36. In all honesty, I don't think 120k miles on these gaskets was bad. Not ideal, but it's not enough for me to rush to the dealer for their latest and greatest!

nosefirst
07-26-2005, 03:55 PM
Ahhhhhhhhhhhhh...

Good point! I'm hoping to put a Supercharger on before then anyway.

Well that probably saves me $$$$ Thanks, over & out.

buccaneer1
08-03-2005, 07:46 AM
Had the same problem two months ago. Had the kit replaced, intake manifold gasket, water pump. Still leaking. Now we were told it was probably a freeze plug that was the culprit. We'll keep refilling until we save our stash back up to make more repairs.

nosefirst
08-03-2005, 10:18 AM
Had the same problem two months ago. Had the kit replaced, intake manifold gasket, water pump. Still leaking. Now we were told it was probably a freeze plug that was the culprit. We'll keep refilling until we save our stash back up to make more repairs.



I recomend putting Bars Leak (available at Napa) in . I read in a similar thread about it stopping the leak for 50k miles. Although it's too soon to tell for sure, my leak has stopped.

If it's a freeze plug it shouldn't be nearly as expensive as the intake manifold. It might be easy to see if your engine is clean. I wash mine off about once a year and it still looks new.

By the way, in case you don't already know, never replace just one freeze plug. Do them all.

buccaneer1
08-03-2005, 10:23 AM
nosefirst:
Thanks, I will keep that in mind.

mikeinut
09-12-2005, 11:47 AM
Had the same problem two months ago. Had the kit replaced, intake manifold gasket, water pump. Still leaking. Now we were told it was probably a freeze plug that was the culprit. We'll keep refilling until we save our stash back up to make more repairs.


I've read all of the intake manifold threads and I feared my '99 burb had that problem as well. I kept losing fluid slowly over several months and I finally found the cause. The "quick-connect" heater hose that is located at about 10 o'clock from the thermostat housing was leaking once the engine heated up. I replaced the whole unit ($8 @ NAPA). I might point out that the metal housing was so corroded from the inside that I broke the metal housing off leaving the threads in the block. I mean I barely started to apply pressure and it broke. I was able to extract it with a long handled ratchet and an extractor tool (i heated it for almost 5 minutes with a mini butane torch). In hindsight I would have just replaced the plastic clip and the o-ring. My leak has stopped. I'm sure I'll still get to do the intake manifold gaskets but, for now, my coolant reservior doesn't go dry anymore.

Just a thought.

pattys
09-17-2005, 10:53 AM
My engine overheated on my 95 chevy suburban very suddenly and I pulled over right away. Apparently all the engine coolant came out and some was found on top of the air filter cover. Being I don't know much about cars, please help! Auto shop replaced heater hose and added 2.5 gals antifreeze. Now only 2 weeks later, truck overheated again. Overfill tank was empty. Auto shop from first repair was closed, so had to tow to a different auto shop who now claims hose was leaking. Claim it's a univeral hose that other shop put on that doesn't fit correctly. This shop also claims they repositioned it and tightened it, but claim I have a very slow leak in the intake gasket. Don't know what to do from here. Believe new shop? Take back to old shop Monday. Take to dealer? I'm afraid it's going to overheat and lose coolant again as I try to take it around to get it fixed. My friend told me that my ex had worked on the housing manifold and had tried to tap out the studs and 1 stud/bolt broke, and said he retapped it out!? I don't understand any of this. Any help or suggestions would be very appreciated.

Derby Driver
12-11-2005, 01:00 PM
Im new hear, and am looking to solve a different problem, but reading yours , I too had a mysterious coolant disappearance, finally found it one hot july day, those darn "quick connectors: on the REAR HEATER BOX, look under the passenger side at the very back of the truck , they were leaking but not enough to drip , just ran down the hose and dried up! so did the "un-thinkable"cut 'em off, and used the standard old fashioned hose clamps (the hex scew kind) did that to my heater hoses on the engine too, however that required a trip to the hardware store for a peice of threaded pipe, $1.29 , havent lost coolant ever again,,,,

instant_vintage
12-14-2005, 10:05 AM
I have questions because it appears I have the same problem.

-Do you have to tell the garage what to check or will they check all of this by giving the description of the problem?

-Would (and if so why/how) this be related to a hard clicking/thumping noise on a cold start that disappears when the engine is warm?

Derby Driver
12-14-2005, 03:59 PM
I have questions because it appears I have the same problem.

-Do you have to tell the garage what to check or will they check all of this by giving the description of the problem?

-Would (and if so why/how) this be related to a hard clicking/thumping noise on a cold start that disappears when the engine is warm?
I doubt the clicking/thumping is related to a coolant leak, UNLESS youve got a head gasket leak allowing coolant to get into the cylinder
and possibly cause those symptoms, you would know because the exhaust would be cloudy white, and smell like burning anti-freeze,
the clicking thumping doesnt sound too good , dont want to scare you
but could be "detonation" (not good) get the timing checked, if it has to be advanced more than factory specs, to run good,,youre gonna blow
a piston, I know, been there done that , #1 took out the cylinder wall too, so had to buy a new short block (OUCH) mines a 7.4 so all said and done it was about $4,000 cnd, runs really nice now though...hope this helps.

instant_vintage
12-22-2005, 11:13 AM
DAMN! well, ya dont know if you dont ask is the old saying. I will get this looked at. Thanks!

RahX
12-22-2005, 11:18 AM
stop leak? thats a bad idea, any stop leak is a bad idea and i dont care what they claim. stop leak stops leaks that arent even leaks, like small passageways in radiators and heatercores.

instant_vintage
12-28-2005, 07:13 AM
Well, i found out that I had a bad radiator cap. I went ahead and replaced that and had my radiator flushed out. As far as the noisey engine, I plan on getting an engine flush next week and hopefully that will answer that problem.

Ketch
12-30-2005, 11:22 AM
I replaced my intake manifold gasket two years ago. Replaced the quick connect with stainless version from dealer and went throught that whole rethreading headache.

Just recently she's loosing coolant but nothing drips. I'm loosing half a tank of coolant over about 50 miles, so this is a fast leak.

I see no leaks on the driveway like before. So COULD IT BE POSSIBLE the coolant drys up before hitting the ground? Seems unlikely....but then again.... seems coolant should not evaporate - thats the whole idea of coolant - not supposed to boil or evaporate away. It can become reduced as the water in it evaporates but should leaves the original syrup and be detectable.

Derby you said rear heater box hose was dripping and evaporating before hitting the ground. How much coolant were you loosing per mile? Where is that "REAR heater box" (which I guess you mean the rear heater core or heat exchanger) and how did you get to it?

If intake manifold gasket is leaking but not dripping outside, there should be coolant in the oil, right?

Could it be running down into the valve train and into the cylinders to get burned up? If so, should there be a coolant smell coming from the exhaust?

As to the freeze plugs, if they were leaking I would see drips on the driveway but nothing comes out.

Lost on this one, any suggestions?

Derby Driver
12-30-2005, 04:31 PM
ya the Heater box in the rear, is on the passenger side, just behind the wheel well, but the hoses/connections you can get from the underside of the truck, in my case it was the connectors that leaked, sounds like you are losing a lot more than I was , and you are right, if it was getting into the engine you would see your dipstick reading increase,
and if it was "burning" it in the combustion chamber, you would smell it and most likely would have white "cloudy" exhaust, anyway come to think of it I was losing about a quart a week, so thats where I would look 1st, also check the lines from front to back, its possibile the leak could run down the length of a hose and "drip" off while driving without showing any moisture on the underside of the truck, also I dont know what part of the world your in, but if you put your heater on does the front window "fog" up on the inside, when it is not below frost temps?
check the carpet under the floor mat (pass side) and feel up as far under the dashboard, could have a leak in the Main heater box, that gets soaked up by the carpet/underlay, if you can take the door sill off
and get your hand in there(under the carpet ) to the bare metal or sound barrier, you might find a big sopping wet floor,assuming you dont have a lot of snow on the floor to melt or a hole in the floor , that would be a dead giveaway to a leaking main heater box,,,,hope this helps,,,,,,,,

Ketch
12-31-2005, 12:50 PM
okay, I took another look at the oil and can see its starting to turn sludgy. So that looks like coolant getting into the oil. I also just noticed the weep hole in the muffler is now spewing water out at a pretty good clip. So something in there leaking into the engine.

I started tearing the top of the engine down to get back to the manifold (what a pain THAT is, tear half the engine apart)....So now the question to be answered, once I get the manifold off, what failed this time? The FEL-PRO gaskets surely would not fail so soon after maybe 15K. So I'm afraid I'll find a cracked manifold or worse, a crack in the head.

I think this way because my original intake repair I over-torqued the bolts thinking it was foot-lbs instead of inch-lbs!!! This was put right to the 11 inch lbs and it held this long so guess what I"m doing NEW YEARS EVE?

Derby Driver
01-01-2006, 10:37 AM
ya, sounds like a head leak to me, check your sparkers, if one or 2 side by side are different than the rest, thats roughly where to look for a cracked head, or head gasket, I know the 454 runs hot anyway, but if you have EVER OVERHEATED< theres a good chance its just the head gasket , which of course is a lot cheaper than head work, having said that, if you suspect a gasket failure , get the heads tested for leakage, and have them milled flat anyway, small $ well spent!

Add your comment to this topic!