Low coolant with no obvious leaks?

[afroman006]

Well my DD crewcab (98 K3500 with 454) has been sporadically overheating and I thought it was a stuck thermostat so today I was going to replace it. I took radiator cap off and saw that it was low on coolant, so obviously thats why it was overheating. I topped it off and it ended up taking a gallon and a half of water. That is alot of damn coolant to leak over a fairly shorty period of time, and I have never noticed any leaks underneath. It does however, have water dripping out of the exhaust. I never thought much of it and kinda figured it was from condensation or something, since the water is clear and my exhaust doesnt "smoke." Could I have a bad head gasket or cracked head?

 

[Masiony]

yes. do a compression check.

 

[JNygard]

Does it have that orange coolant, GM has had a problem with that eating seals or something to that effect. Probably a head gasket or intake gasket.

 

[txfiremank5]

My guess, given the year of the truck would be a head gasket as well. My 97 lost coolant over the coarse of a long period. Not much, but you could see it going down slowly but surely. When I finaly went looking for it, it turned out the be the head gasket. They are pretty common trouble spots for that vintage. I'd have to recommend that you at least give that a good going over in your effort to find the problem.

 

[blazinzuk]

so is this a common thing on all GM engines of this vintage. My 98 malibu has a slow leak that sounds just like that, sorry for the hijack

 

[afroman006]

SSShhhhhiiiiiittttt. That's gonna be alot of damn work to fix...and expensive too.

 

[ryoken]

Pressure test the system... Yet another occasion where that tool is invaluable...

 

[daleearnhardt01]

Its not really as big of a problem on the big blocks but Id say intake gasket ?

 

[sweetk30]

bet ya 5 bucks your malibu is intake gaskets. we do 10 sets at least a month at work.

 

[sandawgk5]

My 87 was doing that and turns out the seal went out on the Water Pump but it was turning to steam so I had no indication of a leak. Just a thought.

Ira

 

[txfiremank5]

so is this a common thing on all GM engines of this vintage. My 98 malibu has a slow leak that sounds just like that, sorry for the hijack

I don't know if it's as common on the 454 or not. I do know that it is not if, but when, on the 98 & 97 350's though. Everyone I know who has one they bought new, has changed it... some sooner than others. I was told it was a bad batch, or poorly designed gasket, and also have heard that the dex-cool is partialy to blame. I don't know about the dex-cool, everyone has their own opinons about that, but I have been told by several mechanics that the gaskets are poorly designed. The new gaskets are better. Mines been done a while now with no coolant loss at all. Same results with everyone I know who replaced the gaskets.

 

[theperfectgarage]

yes. do a compression check.

better yet, Leakdown test.

 

[1985_K5_Silverado]

You could check your oil level, to see if it's unusually full (because of coolant leaking into the crankcase).

 

[afroman006]

Nothing unusual as far as the oil goes. I'll do a compression test and see what it says.

 

[redneck396]

I would pressure test the radiator also.

 

[redneck396]

Also on the under side of the waterpump is a weep hole. usually you can snake your arm in there and wipe a finger across it. If it comes back wet you need a new water pump. if you decide to do the compression test take a careful look at your plugs. they will be wet and possibly have a white powder residue around the edge.

 

[diesel4me]

another test...

I second the pressure test..also,many shops here use the exhaust gas "sniffer" used for emission inspections to detect bad head gaskets or cracked heads and blocks...they run the engine with the radiator cap off,and hold the probe just abouve the coolant..it will detect even slight traces of exhaust hydrocarbons..

I've had a few motors with no detectable external leaks,but they used a pint or more of coolant every few weeks..I suspected cracks in the heads between the valves,having seen many that way at work--such a slow,minute leak,it goes right out the exhaust-- it does not contaminate the oil...I added a tube of "Aluma-Seal" stop leak powder,and rarely had to add any coolant after that..might be worth a shot..but it wont work for long,if at all,on a head gasket leak,no stop leak will,regardless of what the package says..

 

[peter redman]

at work i had a 89 chevy van with a 305 that had the same problem.the driver really overheated the motor to the point that the mechanic who was looking at it said the van needed a new motor.work decided that the van wasn't worth it and gave it to me.when i fired it up it ,it went thru 10 gallons of water at idle due to the blown head gasket.i then headed off to lordco and picked up a bottle of irontight block seal.my buddy who was followig me had turn on his windsheild wipers on a warm summer day because of the water loss.2 miles later the smoke stopped and drove the sun of a gun 40 miles home with no problems.i later vsold the van and 3 weeks ago spoke to the new owner and he has had no problems since and he has put 30k on it.another way to quickly check if the head gasket is gone is to remove the rad cap ,start the motor with a full rad and see if the rad water is bubbly and or frothy.if so blown head gasket.