Coolant mysteriously dissapearing...

nosefirst · #1 07-23-2005, 05:38 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 · #2 07-23-2005, 07:37 PM

Quote:

Originally Posted by nosefirst

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 · #3 07-25-2005, 10:57 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 · #4 07-25-2005, 12:53 PM

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 · #5 07-26-2005, 10:34 AM

Quote:

Originally Posted by nosefirst

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 · #6 07-26-2005, 12:57 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?

suburban_lee · #7 07-26-2005, 02:43 PM

Quote:

Originally Posted by nosefirst

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 · #8 07-26-2005, 04:55 PM

Ahhhhhhhhhhhhh...

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

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

buccaneer1 · #9 08-03-2005, 08:46 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 · #10 08-03-2005, 11:18 AM

Quote:

Originally Posted by buccaneer1

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 · #11 08-03-2005, 11:23 AM

nosefirst:
Thanks, I will keep that in mind.

mikeinut · #12 09-12-2005, 12:47 PM

Quote:

Originally Posted by buccaneer1

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 · #13 09-17-2005, 11:53 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 · #14 12-11-2005, 02:00 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 · #15 12-14-2005, 11:05 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?

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