The Oil Lab told me that: if there is coolant leak into the oil and the coolant is burned off during the engine operation, they look for:
- Na (Sodium)
- K (Potassium)
- Silicon

Here is what I found on the internet for reference purposes:
Contaminant Metals - Silicon, Sodium & Potassium

 

Update...

This is the engine oil analysis on my other vehicle, 2007 Honda Odyssey Family Van with 52K miles. I think this is also relating to any gasoline engine so here you go...

---> Na (Sodium) 840...(should be zero)
---> K (Potassium) 2076...(should be zero)
---> Glycol: present...(should be zero)


Symptoms:
- Misfire #1 and #3. Swapped ignition coils, reset OBD-II codes, symptoms went away....but
- Engine drinks coolant mysteriously 300cc every 5-10 miles! No external leak, no coolant on the garage floor.
- I drained a cup of engine oil for lab analysis ($15 for the lab test).
- Sent the Van to Honda dealer to confirm. Tech kept the van for a few days and confirmed engine drinking coolant as above.
- All kinds of tests were done (cooling system pressure test, engine compression test etc.): all normal! They were stumped as the van has only 52K miles and meticulously maintained.
- Then I received the lab result! Wow, Na (Sodium), K (Potassium), and Glycol in engine oil! I gave the Honda dealer a copy, they were stumped as they have never done engine oil analysis in any car before. Now they know there is a local lab that can perform engine oil analysis.


The bottom line:
- Honda Tech pulled the Intake, sure enough moisture.
- Pulled the cylinder head: sure enough microscopic crack, basically Aluminum casting flaw from factory that only shows up at 50K, in my case.
- Per Honda HQ, they have seen this before but only in 1 in 1000 cars etc. A case in Florida, another case in NY etc. Basically a very unusual problem.
- The good news: the Honda van is still under 5y/60K power train warranty. They will install 2 new cyl heads ($900/each). Wow, if the car is out of warranty, it is about $3000 bill. Luckily, it is still under 5y/60K power train warranty.


The Morale of the Story:
- If your engine drinks coolant mysteriously, do an engine oil analysis for $15. There should be some local labs that can do this for you.
- If you ever overheat any car and suspect head gasket leak or cracked cyl head, do an engine oil analysis for $15. It is inexpensive and easy diagnosis before you embark on a 20-30h rebuilding the cyl head!

Anyway, I will update this thread further once I get the van back next week.

 

Update,

Got van back from dealer.

It was a cracked cylinder head. Repaired under warranty (5y/60K).
Honda gave me 2 brand new cylinder heads (not rebuilt).

All is good now, no more coolant consumption.

This was probably 1:1000 case kind of thing!

 

Our van is using coolant as well.. I will send out my oil and let you know what they find. I did change the oil about 500 miles ago, should I wait or take a sample now?

 

cnn, what lab did you use for oil testing? Do they work via mail?

 

It really doesn't mean anything how high it is in the reservoir as long as there is enough to keep the pickup hose in the bottom of the tank under coolant. As the engine heats up the coolant in the engine expands and pushes any air and coolant out the cap to the reservoir. As the engine cools down it sucks the coolant from the reservoir back into the radiator preventing any air in the radiator. The main reason for the high/low markings is to ensure there is always enough coolant to prevent drawing air into the system and also a quick indication of usage which would mean a leak somewhere. You could fill it to the top if you wanted with no ill effects other than it would overflow when the engine overheated. Just don't let it get too low.
As a reference my 04 with 55k has never had coolant added.

 

Bringing an old thread back....

I have found that between oil changes (every 5K-6K miles), the coolant reservoir goes from Max to about 1" below Max.
Add 1/2 cup and it is back to Max (measured in the morning with COLD engine).

Assuming that:
1. Your engine is normal, no head gasket issues.
2. Your radiator and cap are fine, no leak.
3. Your reservoir and cap are fine.

What is your rate of normal evaporation from the reservoir?

 

cnn,

I don't think there is any normal evaporation rate. I haven't added any coolant to our 2001 for 2.5 years and its level has remained constant over that period. The coolant is due to be changed again, but I will wait for some warmer weather first).

 

Bought my hunk of crap in Oct 2003. I never had to add coolant and I just dumped it Nov. 1st.

Now gas...that's another story.

 

redmondjp,

My question is mostly for 3rd gen Ody...

I sold my 2001 Ody in 2007, during my 6 years of ownership of the 2001 model, I never had to add coolant to the reservoir.

I bought the 2007 Ody new and there is something peculiar about 3rd gen Ody, the coolant seems to disappear slowly, either from evaporation from the reservoir or internal consumption (I will send my engine oil for analysis in the Spring and report back if there is any coolant in the oil, hope not).

Stopped my Honda dealership yesterday and the mechanics told me that at every oil change for their customers, whether it is Accord, Civic or Ody models, they frequently have to add 1/3 ---> 1/2 cup of coolant to the customers' cars.

My theory is: Honda (and many Japanese cars) have an open system where the reservoir can vent into the air (open system).
Whereas Euro cars (Volvo, BMW etc.) have closed system.

 

I'm with you, but the 2001 has the overflow reservoir vented to atmosphere as well, so I don't know how that would explain the difference between that year and the 2007. I know what you are talking about with the closed systems (pressure relief cap on the plastic reservoir instead of on the radiator), and they were not limited to the foreign makes either - a lot of domestic vehicles have the same setup (such as 1996 Taurus I just worked on, my neighbor's 2000 Grand Am, etc.).

It is an interesting comment from the dealership though about having to regularly add coolant - I wonder if it has to do with the engine compartment temperature and the location of the overflow reservoir?

 

I had the same issue w/ coolant loss this fall with our 2008 EX. I was able to spot a small leak in the radiator, about 6 inches up from the bottom. A new radiator fixed the issue. I feel really fortunate to have identified the issue. The leak had gotten so big that the coolant overflow tank would be emptied overnight. We park in a gravel parking spot, so I didn't notice coolant dripping on the ground.

I also plan on getting the oil tested to check for coolant contamination.

 

Something I haven't seen mentioned, when your waterpump starts to go it will slowly leak antifreeze from the weep hole. If you have an older vehicle that is something to consider.

 

I had exact same issue of coolant leaking slowly and it turned out to be a bad heater control valve which was leaking the coolant (very minute amounts). Replacing the heater control valve solved it in my case.

 

This may sound silly but I had the same problem the only thing was we changed the radiator cap and everything was fine and burped it. That was on a 2008 Odyssey and it's running great now it's just I can't believe that was a $3 fix

 

changed the radiator cap and everything was fine

Welcome to the forum.

A bad seal between the radiator cap and the neck can cause loss of coolant.

Good example of the old adage: try the simple stuff before digging deeper.