I'm gonna post this here as I didn't get many responses in the Mod motors section of the forum. I'm noticing the coolant level dropping and have some questions. As background: 2006 E250 with 350k miles on the chassis, ~150k miles on reman'd engine.

Coolant is about a 1/2 inch low after 1 week/70 miles when engine is cold. Level is a bit above cold fill level when engine is hot. Varies. Pictures incoming.

I figured intake manifold gasket was bad. Local mechanic did a pressure test - 30 mins of no pressure loss at 18 psi. He doesn't think it's the intake gasket, wants me to keep an eye on it.

I did a "block test," - negative.

More background: A mechanic two years ago diagnosed blown HG from compression test. Another disagreed just last month, finding bad coil and spark plug causing 7 cylinder operation, plus three bad O2 sensors. He said unburnt fuel in cylinder could account for funky compression test. Van runs great now, no overheating, no white smoke.

I have a P0420 code indicating replacement of bank 1 cats. Power graph on scanner shows even power across all 8 cylinders. No white smoke. No signs of coolant leaks. Do have occasional blue smoke, suspect valve stem seals.

Before I put a lot of money into replacing the cats, I want to be sure where the coolant is going.

Did the UV dye last night. No sings of leaks so far. No coolant smell from exhaust pipe. No milkshake on dipstick or under cap.

Questions:

-Will a pressure test show an intake manifold gasket leak?

-How much does coolant level fluctuate? Could this just be level fluctuation and I'm chasing my tail?

-How do I know for sure it's not burning the coolant?

-Does coolant ruin cats? Per the other thread it sounds like no.

 

Top is engine cold, bottom is engine hot. It was filled to the line when cold last week. Thoughts?

 

A pressure test should expose manifold and gasket leaks but there's probably coolant pooling in the corners where the manifold meets the head if there's a leak. Your nose is pretty good at detecting coolant leaks too.

For head gasket integrity, check for exhaust gas in the cooling system with a simple tester available to 'borrow' from most auto parts stores: Rental Tools EverTough Combustion Leak Tester 67094 | O'Reilly Auto Parts

I check coolant level first thing in the morning and not during trips. Yours looks a tad low but I wouldn't worry about it. If you must, fill it to the Cold Fill Level after the van has sat overnight then check it after the van has sat overnight. What the level is with the engine running can vary. That's why there's all that space above the cold fill line.

Sixto
07 E350 5.4 200k miles

 

Thanks! I did the test for exhaust gases in the cooling system, what I called a block test. It was negative. I don't smell coolant. Sometimes there's a slight whiff by the radiator, but even that I don't smell sometimes.
Thanks for the tip on checking coolant first thing. Before I filled it to the Cold Fill Line, it was down at that small black dash I made with a grease pen.

 

I've been seeing my antifreeze level fluctuate as well. i found the top of the radiator plastic cap had a leak. it sprayed out to the same level as the reservoir tank. waiting for a radiator now...

 

I appreciate the response. I'm confused, your van has a radiator cap? Or do you mean the plastic top on the radiator? Mine only has the screw cap on the reservoir tank.

 

yes the plastic top of the radiator.

added info.
i noticed the reservoir tank was low . after adding antifreeeze and driving, it was low again with antifreeze sprayed onto bootom of hood and wetness on top of radiator. leaking there.

 

Your head gaskets are the small internal leak
Some only leak hot and running
If a little coolant weeps around, past the head gaskets and gets burnt, you won't necessarily see that on a dye test
You also won't see it loose pressure at 18lbs sitting there static

 

@pancake52 I'm curious, how did you locate it?

 

@manicmechanic007 Thanks for your response.

A few questions:
1. Would that not show on an exhaust gas test of the coolant?
2. Would a pressure test on a hot engine show it?
3. Do you think that a small leak into the combustion chamger like what you're describing would ruin the new cats I plan to install?
4. And would using a head gasket sealer be prudent?

 

Sometimes, sometimes, no, no.
1 We used out exhaust gas analyzer from the I/M machine looking for HC in the coolant (held the exhaust probe right over the open radiator cap with the engine running)
Otherwise it's dye and that does not fluoresce every time (it does, it's just hard to see)
2 It has to leak real bad to drop pressure using a pressure tester. head gasket seep will not usually drop pressure any more than the tool itself drops
3 No, cats can handle antifreeze just fine, even major head gasket failure (tons of white smoke) does not take out converters
4 No, it will plug up the heater core, and possibly the radiator too, and still leak a small amount into the combustion chamber

 

Thanks for the response.

Hearing what you've shared, I guess I'll just replace the cats so I can pass emissions, and just keep an eye on the coolant then. What's odd is that after it gets about half low (the small black mark on the tank), the level stops dropping. Any ideas why that would be?

 

What? You have a P0420 or P0430? code
If so, then yes, replace the cats with the cheapest one you can find on Ebay
Ideas? Some cars push some coolant out and want to be a certain level
My old hotrods will not allow the radiator to be completely full
Some vehicles if there is a pinhole in the radiator the level will drop to where the pinhole is
Yours should have no pinhole if the pressure holds and there is no external leak
Head gasket seepage is about normal for cars over 100k miles and even earlier on say a mid 90's Taurius 3.0-3.8 with a iron block and aluminum heads (like your 4.6)

 

Yes, a P0420 code.

Thanks for the ideas. Appreciate you sharing all that information. One of the things you described must be what's going on.

I just received the new cats in the mail, I hope it fixes the code. Cheers.