About every month I have had to add a 1/2 gallon or so of coolant when the light comes on. Oil tests no glycol contamination. Is the next step pressure testing from a radiator shop, and request they test for presence of combustion gasses? Top of expansion tank moves when I tighten radiator cap. I hope this is the culprit.
Enthusiast
Don't know if it will help, but a year or so ago I found a leak in the block heater that was allowing a small amount of coolant to leak out. I park on dirt and gravel, so I didn't notice it for awhile. Took some time to find, but finally did. I too worried that it was a cracked head. It was where the terminals are soldered into the body, one had broke loose and allowed a drip. Hope it helps.
Chris
1997 K2500 6.5L, Ext. Cab, Long Bed
-Max-E Tork
-Turbo Master
-H2O Injection
1999 Trans Am - 6sp, LS1
Enthusiast
My leak is from the heater tube going into the thermostat housing.. I can replace the o-ring and it is fine for a month or two then the leak starts slowly then progressively gets worse.
Phil
2007 Metallic Blue GMC Crew Cab 2500HD LBZ Allison. 70K mi, 255/85r16 tires.
1996 GMC 2Dr 4wd Yukon 190k mi, 3.42 rear end, 265/75r16 tires, 4l80e, 97 cooling mod, D-max fan blade, Hayden Severe duty fan clutch, Autometer Boost EGT Tranny temp, JK's 3.5 exhaust.
Reno NV.
Enthusiast
Dihrdbowt, if you are referring to the green hose with the aluminum ends that comes into the hosing via that plastic clip together thing-a-ma-bob, I too had that leak and replaced it with a brass nipple and hose. No problems since. I guess that clip was to help with the assebmly process at the plant, but if it gets moved too much, it starts to leak.Originally posted by Dihrdbowti:
My leak is from the heater tube going into the thermostat housing.. I can replace the o-ring and it is fine for a month or two then the leak starts slowly then progressively gets worse.
Chris
1997 K2500 6.5L, Ext. Cab, Long Bed
-Max-E Tork
-Turbo Master
-H2O Injection
1999 Trans Am - 6sp, LS1
James,
The top of the expansion tank on my '99 moves about 1/8 turn when I remove the cap. The system appears to hold pressure when hot for me. Upper rad hose squeeze test.
I'm sure you have checked the hose clamps. My lower rad clamp was a bit loose, tightened it up about 1 turn. In the winter, it would leave a puddle on the drive. Plastic contracted more than the hose while using the worm gear clamp. Thinking about going back to the OEM style that applies constant pressure.
Hope this helps
HammerWerf
Enthusiast
Chris,
Yeah it's the plastic thing-a-ma-bob clip that goes into the thermostat housing. Mine is a hard line all the way to the back to the block. I just haven't decided to get really motivated about fixing it permanently. maybe next month when I'm due to change the o-ring.
Phil
2007 Metallic Blue GMC Crew Cab 2500HD LBZ Allison. 70K mi, 255/85r16 tires.
1996 GMC 2Dr 4wd Yukon 190k mi, 3.42 rear end, 265/75r16 tires, 4l80e, 97 cooling mod, D-max fan blade, Hayden Severe duty fan clutch, Autometer Boost EGT Tranny temp, JK's 3.5 exhaust.
Reno NV.
Hammerwerf, what is the upper radiator hose sqeeze test; motor running or cold? What should I look for?
James,
When the engine is up to temperature and should be at pressure, squeeze the upper rad hose. If the radiator cap and head tank are holding pressure, the hose will be firm, as the internal pressure is pushing outward in the pipe. It will still squeeze down as the system is not solid to the top with water, but you should feel a difference between a hot and cold system. I use this "test" especially on my 84 as the radiator system is spotty at holding pressure.
HammerWerf
When you start the truck after it has set over the weekend does it seem to be smoking more than normal when cold, also do you smell antifreeze at the tail pipe when you first start the truck. There is a product out on the market made by BARS it is called Headgasket and Block Sealer. It works well if you follow the instruction to the letter, I have a fleet of 180 6.5 I work on I have used this several time with great results it has saved me from replaceing heads on 5 truck in the last 3 years, I have one truck I sealed up 3 years ago that was letting water into the cylinder it is still running and not using water. It doesn't always work I've had 2 that is slowwed the leak however still had to tear down and replace the heads. If you have to replace the heads I have found that the replacement head from Alabama Cylinder Heads are a good deal $325.00 each better than the $795.00 from GM.
good Luck
Well, top radiator hose is soft when cold, and soft on cold start; exactly the same in fact. Hopefully this means no combustion pressure on cold startup. Will check pressure when heated later.
Top radiator hose hard when hot. So it is holding pressure. Noticed white stains below the clip contraption that goes into the thermostat housing. That is probably where it is leaking. Boy, I feel better!
Enthusiast
How hard is your top rad hose getting?
1998 Z-71 X-cab 4x4<br />amsoil, 3\" downpipe & exhaust,isspro boost & pryometer,timing at -1.53,<br />duramax 21\" fan,DSG reprgrammed computer,boost controller
Enthusiast
I was adding about the same amount of coo;ant as you. I noticed the white stuff around fitting on the t=stat housing as well but didn't believe it could be leaking that bad from there. Wrong!!! Since I changed the fitting no more adding cooling.
Pat
95 6.5TDGMC K2500<br />4\"BD exhaust and downpipe<br />airbox mods 97 cooling mods JK fan clutch Duramax fan Isspro egt and boost maxi-torq 2
I can't squeeze it when hot. When cold can squeeze easily; can hear water squishing.
Enthusiast
That is what mine is like right now and I don't think it is right
1998 Z-71 X-cab 4x4<br />amsoil, 3\" downpipe & exhaust,isspro boost & pryometer,timing at -1.53,<br />duramax 21\" fan,DSG reprgrammed computer,boost controller
Enthusiast
When the thermostat opens the system is under 15# of pressure as long as the surge tank cap is working. I've found that if the top radiator hose is hard after a minute or so of running when cold, the exhaust pressure is getting into the coolant system.
The telltale signs of the white powder is deffinately one source of a coolant leak. it's rare but you can develop leaks at the heater core too. Feal around the carpet at the heater core.
White smoke out the tail pipe and/or a coolant smell here is not good. Be careful using the "Bars Leak Stop". This can cause a host of other issues down the road.
Charlie P. <br />95 Tahoe 6.5 TD
Enthusiast
So your saying there will be 15 psi on the top hose at all times once the thermosats open?
1998 Z-71 X-cab 4x4<br />amsoil, 3\" downpipe & exhaust,isspro boost & pryometer,timing at -1.53,<br />duramax 21\" fan,DSG reprgrammed computer,boost controller
Enthusiast
The entire coolant system is designed to hold 15#. Diesels' are generally a few pounds more than gas engines. This pressure is why it's hard to squeeze the top hose after the thermostat opens.
Charlie P. <br />95 Tahoe 6.5 TD
Well my leak has finally come to a head. Looked under truck today while parked at my parents house and say large puddle of coolant and a slow drip. I dropped it off to be fixed. I will advise.
S&S tire guy said it looked like it was coming from the water pump area, and declined to proceed further. Water pump was replaced in 2003, 37,000 miles ago. I have never had a water pump fail that fast. Is there a source that leaks in the same area as the water pump? Made an appointment with the diesel mechanic who replaced my WP on Friday.
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