Cummins93

What does the underside of your oil fill cap look like? Do a block test.

ChrisG

Thanks guys. Ill post the results when I get them.

ChrisG

What's a block test. Sorry all of this is over my head.

Cummins93

https://mobiledistributorsupply.com/...FVyBswodbsoJKg

The fluid comes separate. Napa part number bk700-1366.

Fill the tester with fluid to the line.
Take off rad cap while engine is COLD.
Put the tester in the filler neck of radiator.
Place aspirator bulb in top of tester with valve facing up.
Start engine and allow to reach operating temp.
Squeeze aspirator bulb to draw radiator gases through tester and note color change.

If fluid changes from blue to yellow or clear than co2 is present in the radiator. This indicates a leak from the combustion chamber, where co2 is created, to the water jacket. If you do a fair amount of automotive work you will use this kit many times.

mikesignal

I have a 2000 and had the exact same issue. I installed a new clearwater head and new Fel-Pro head gasket and no more coolant loss. FWIW my oil analysis came back good, and there were no exhaust gases in the coolant. Not saying don't do the tests, just saying be prepared to replace the head.

moparado

If its a cracked head losing that much coolant, the oil will definitely be milky but you say its not. And oil psi is also normal.

If the oil analysis comes back clean then i'd suspect a blown head gasket.

nujeepguy

compression check?

mikesignal

To each his own, I just don't see the point in putting that p.o.s. 0331 back on. For me it was a big job, the first head gasket I ever did, so I wanted it to last and did not want to take any chances. My cousin had his resurfaced and he put it back on with a new gasket. It's been about a year and a half and it's still good. A friend of mine has 280k on the original head and gasket; I guess he got lucky

investinwaffles

Ok, first things first - have you pulled the valve cover off?
It takes like 30 minutes to remove (or 5 mins if you do it as often as I end up), and you can inspect the topside of the head for cracks. You have an 0331 head which usually cracks between the #3 and #4 cylinder, google images should have a few reference images so you know what to look for.

If you can't see any cracks, you will want to move on to "leakdown" test and compression test.
Also, you can drop an inspection camera down into each cylinder through the spark plug hole and check the pistons themselves, if one is very shiny you have coolant seeping into the cylinder chamber (either through a blown head gasket or a crack on the underside of the head). I got one for like $10 and it is pretty handy
http://www.ebay.com/itm/USB-Borescop...js9bxcSu_BpPQw

Get on it quickly if the compression check comes back good - or else you will kill the motor over time.

Worst comes to worst, pull the head off the motor and have a good machine shop check it for cracks or any other flaws (and replace the head gasket at the same time)

IJM

If you're in a hurry, Blackstone has instructions on their website (FAQ page?) about using your own container to send in a sample rather than waiting for one of their kits to arrive.

ChrisG

Investinwaffles - Sorry it took me so long to get back to you but I sent your question to my mechanic and he has he did all of that. Including the compression test and camera inspection. All good.

mo8414

Maybe the heater core is leaking?

alpine.adrenaline

x2- that's the only part that hasn't been mentioned and is prone to leaking. OP- any funny smells or damp carpet? I would think a pressure test would show but if it's a slow leak and you've got crud in the core...

moparado

Adding a gallon of coolant a week, i'd think the OPer would know if the heater core is leaking by now. The interior would be soaken wet.

extrashaky

It would not definitely be milky. It will turn milky if you're using oil that doesn't have a very good detergent package. I was using Mobil 1 in mine, and it never turned milky at all despite the oil level rising visibly between oil changes there at the end.