Losing Water

[HelpPlease]

hd2500 duramax diesel losing water 1/2 gallon - heating up to 210 degrees. No water drip, nothing out the exhaust - what could be the cause.

Getting air in the water system.

New water pump and thermostats.

[rapidoxidationman]

Is the cooling system pressurized even when the engine is cold?

[a5150nut]

Do the DMax's have an air bleed like the 6.5s?

[rapidoxidationman]

There's an air bleeder on top of the dual thermostat housing, IIRC.

[Kennedy]

hd2500 duramax diesel losing water 1/2 gallon - heating up to 210 degrees. No water drip, nothing out the exhaust - what could be the cause.

Getting air in the water system.

New water pump and thermostats.


Not the news you want to hear, but sounds like the thermostats and water pump were misdiagnosis of the real problem.

This sure says head gaskets to me. Put a bottle on the overflow if the surge tank once and see if you can trap anything.

The bad news it's an expensive job, but the good news is that if done properly they do not repeat in my experience.

[DmaxMaverick]

Welcome aboard, Help!

If the system hasn't been properly bled, it can take a while to get all the air out, and coolant in. Just topping off the pressure tank alone can leave it more than a gallon low.

The bleeder bolt on the thermostat housing should be open while initially adding coolant to the pressure tank, after the system has been open and the coolant level has decreased below the thermostat housing (such as a water pump service). Once coolant comes out of the bleeder, close it (don't open it again after this). Slowly top off the tank, to about 2" below the filler, install the cap, but leave it about 2 turns loose (open vent, no pressure held). Start the engine and idle for about a minute or two, but not enough to reach operating temp (stats not open yet). Increase engine RPM to 3,000 and hold for 10-15 seconds (don't worry, it won't hurt anything), then return to idle while you check the coolant level, and top off as before. Repeat this until the engine reaches operating temp, and the coolant level no longer decreases. Close the pressure cap and drive normally. It may take an additional 1/2 gallon of coolant (typical) over several miles and time, so check it regularly until it's stable and holds the full-hot level. Some trucks will bleed much easier and sooner than this, but some take a lot of time and work to get it complete. In any case, it shouldn't take more than a couple warming cycles to complete, and additional coolant should decrease each time. If it continues to take a lot of coolant after a week of light driving (or a day of heavy loaded driving), you may have another issue in the works, but don't get alarmed before that.

[CoyleJR]

My truck was always (over 100k miles) running on the low side of the coolant fill tank. About six months ago I replaced the radiator/fill tank cap and now it stays exactly on the full mark. That is even with hauling a heavy 5th wheel trailer in the 120 degree Az heat. I would suggest replacing the $7.00 radiator cap and see if it helps.
Good luck
John

[More Power]

The last time I filled the cooling system in a Duramax powered truck, I parked it nose up, diagonally on a 15 degree slope, with the coolant surge tank at the highest point. That got the air out first time with no need to topoff later on.

Just a thought.... Jim

[rapidoxidationman]

Just curious: Did the water pump get replaced because it had a bad seal and was weeping coolant?
The overpressure condition created by a blown head gasket can make the water pump go bad. I'd love to ask the engineers why the overflow tank cap popoff pressure is higher than the maximum pressure the water pump can handle, but I suppose that's a topic for another thread...

Like Kennedy says, a head gasket job isn't cheap (count on $5000 plus at a dealer) but if you've got skills to do it yourself it can be done for about half of that - and that'll include some valve and head work and ARP studs to hold the head on instead of the "cheap" ones that are on there now. I did mine with about 200 cell phone pics, 5 very full pages of notes, and a subscription to AllData. And an occasional piece of advice from a mechanic friend.

[HelpPlease]

Cooling system is pressurized even when cold.

Temp is rising to 210 when going up hill, let off the throttle it drops down to about 190. Driving on flat ground runs about 190.

Still losing 1/2 gallon of water= heater is blowing cold air.

Water overflow prior to getting the water pump and thermostats replaced. Now not putting water anywhere just losing it. Has about 118K miles 2001.

When thermostats were replaced it quit throwing water out of the overflow.

Now they're saying that it may the headgaskets but that's expensive as you've all said, got same quotes.

Not losing power, no water in the motor oil, no water coming out of exhaust. Thanks for all the answers.

[rapidoxidationman]

Heater blowing cold air = water pump that is no longer pumping water. Unfortunately, experience has shown me that it can happen even with a new (OK, 6 months old) OEM water pump - the shaft and impeller are only pressed together).

If you're brave, meticulous, and can gain access to a couple of specialized tools (a flywheel holder for breaking the crankshaft pulley nut free and a fan removal impact tool) you CAN do the head gaskets yourself in about 60 hours. A machine shop can make sure the head surfaces are nice and flat, and they'll also be able to clean up the ports and intake manifolds. Kennedy can sell you the parts you need (gaskets, injector lines, and a water pump if needed) and I'll bet most any question you might come up with can be answered here. All you need is a dry and well lit place to work.

Take the hood off, take the front wheels off, and lower the truck to the floor. Take a deep breath and start removing all the plumbing... Take pictures at each step. Take notes too. I started a thread about 1.5 years ago on how to replace head gaskets. I never finished it, and it's about the LLY not the LB7, but it might give you inspiration.

Ahhh. Here it is:

http://www.thedieselpageforums.com/tdpforum/showthread.php?t=39924

You can do it for at least half of what the dealer will, you'll know it is done right if you're paying attention, and you'll learn a LOT about your engine.

[Kennedy]

Cooling system is pressurized even when cold.

Temp is rising to 210 when going up hill, let off the throttle it drops down to about 190. Driving on flat ground runs about 190.

Still losing 1/2 gallon of water= heater is blowing cold air.

Water overflow prior to getting the water pump and thermostats replaced. Now not putting water anywhere just losing it. Has about 118K miles 2001.

When thermostats were replaced it quit throwing water out of the overflow.

Now they're saying that it may the headgaskets but that's expensive as you've all said, got same quotes.

Not losing power, no water in the motor oil, no water coming out of exhaust. Thanks for all the answers.

Pretty much says head gasket to me.

There's a lot of hours of labor in the job. As stated, the DIY factor is a true possibility IF you have patience and time. We plan about 40-42hrs in the job. We have the heads skim cut the bare minimum that cleans the surface. Cleaning the deck is done with a razor blade and maybe a piece of scotch brite or plumbers open emery cloth. Studs are a definite and we do NOT use the latest GM gaskets that have the layers all individual, we use the style with the wrapped fire ring.

We start another LLY head gasket/water pump job Friday. We typically remove the engine and work on a stand so access is free and clear for cleaning, valve adjustment, etc.

[Kennedy]

What year truck is this?

If it's LB7 the advice changes and so does the cost.

As for removing the hood we do NOT remove the hood. Just remove the ground strap and take out the 2 bolts where the hinges attach. Open the hood until vertical and put the bolts through the extra holes that hold it in the service position.

[Mark Rinker]

What year is your truck? 2001s were known to have head gasket issues, especially if they were 'turned up'.

My 2001 first started pressurizing in the dead of Minnesota winter, blowing LOTS of coolant out the overflow, whenever it was cold enough outside to cause both thermostats to close.

In more mild weather, it was hardly an issue. I sold the truck (with full disclosure) to a couple guys who intended to fix and re-stud the heads, using the truck for a truck pulls. Took the 10k sale price + the 5K saved and put it down on another 24K truck, five years newer and with 1/3 the miles.

[More Power]

Scotch Brite is generally not recommended because abrasive material can find its way into the engine. GM recommends 600 grit wet/dry paper on a flat sanding block to prep the deck. However, using a razor blade sounds like a good idea to remove any of the old gasket material first.

Jim

[Kennedy]

Isn't emery and sandpaper abrasive? I would think that either of these would sluff off more than a piece of scotch brite.

To me no matter what you use it's abrasive and it's going to leave materials that are unwanted. Clean up as best you can and do an oil change shortly after buttoning up.

[More Power]

That's what the GM service manual says.... about prepping heads/blocks.

Sanding blocks and 600 wet/dry will produce some particles, no doubt, but it remains localized and can be cleaned off. I'm told the worst thing to do is use a powertool with a scotch-brite like wheel, which flings the abrasive material into the air and into exposed areas of the engine. Jim

[Yukon6.2]

When we had our shop open ,the engine supplier we had at the time included a warning with the paper work on the engines.It basically stated if any sign that a abrasive wheel was used on the cleaning and assembally,the warrenty would be void.
And they ment it.We had to eat the cost of one engine.Our mechanic would not listen the first time,most of the time.Don't know where he is now.
Thomas

[Kennedy]

Absolutely no power wheel stuff, but a hand pad of scotch brite has interwoven fibers that stick together.

My preference is plumbers open emery cloth and single edge razor blade.

Score an old head bolt up each side with a thin wheel and use that to chase the threads clean.