Losing Coolant, BUT, pressure test found no leaks

[rvwarrior]

So, I did a pressure test on the cooling system today

1995 5.9 Cummins

It appears that there are no leaks in my lines

So, how could I be losing coolant all the time

I'm not losing a ton, just enough to run my overflow reservoir down about half way when I do 300-400 mile runs.

Could my coolant be evaporating too fast because of a dirty radiator?

Could this be a water pump issue?

When I'm driving and the engine has a load on it, could it then be leaking from somehere else?

Thanks guys

s

[RV Mech Tech]

rvwarrior- if you are loosing coolant and you do not see any external leakage then its possible you may have an internal leak from the coolant passge to one of the cylinders through the head gasket or o-rings on some diesels - if this is the case then it sounds like it may be a small leak and when the engine is running the cooling system is under pressure and the coolant is escaping and going into the cylinder and being burned- you may not see it if its just starting but if it gets worse you will se it out the tailpipe as white smoke- another possibility is that instead of going into a cylinder it is leaking into an oil passage - there are both coolant and oil drainback passages that are in both the block and cylinder head with the head gasket sealing them and keeping the fluids seperate- any defect and one can leak into the other- check your engine oil for any contamination - the oil will take on a brownish milky color when coolant mixes with it- there is a test kit that techs use to test coolant contamination - its a chemical test something like a litmus test and if there is any contamination in the coolant it will show up - there is the same test for engine oil as well - if you suspect this is the case have it checked out soon- if you catch it soon enough you may be able to prevent very expensive engine damage- let us know what you find-

[rvwarrior]

Thank you RV Mech tech

Hmmmm. This sounds interesting

The good news (possibly) is that I did an oil change about 4 days ago and the oil still looks jet black

Is this something that a skilled diesel mechanic would be able to look at without tearing into the engine and costing me $$$$??

I'm heading to Omaha next. I know a good mechanic at the Omaha Truck Center.

I will show him your post, but other than that, how should I verbalize this problem?

Basically, is what I could possibly have a "internal leak from the coolant passage"?

Is that how I put it to the mechanic?

I want to avoid having a mechanic spend hours ($$) trying to figure out what the hell it is that I'm talking about haha

When it come to RV's, I swear, I'm aging in double time

But it's worth it

shad

[drifter]

Somebody posted a similar problem not long ago; I guess it was on another forum. They had it tested at more than one dealer (I think it was a Ford chassis) and never found a leak yet after a long run, it would be low on coolant again. Finally, the guy noticed that the leak was in the line going from the radiator cap to the overflow tank and it wouldn't leak unless under load and hot.

You may not even have an overflow tank on a diesel pusher - I don't have one on my Discovery - but it may be that the radiator cap is old and somewhat weak (there's a lot of that going around) and not holding well when hot and under pressure. Lots of things can leak under those circumstances but anyway a new cap costs less than having it tested. Be sure to match the psi rating.

[rvwarrior]

Hey Gary,

Thanks for taking my call today

I think we scared off the mechanic haha

Yes, you are correct, I don't have an overflow tank. Just the resorvoir where I put the coolant into.

BUT, I never thought about the cap - hmmmmm

You know, you just never know! Stranger things have happened

Usually I'll spend a few hundred bucks figuring out it was a $3 problem

How do I check the PSI rating? Is it written somewhere on the cap?

I'm currently weathering a Tornado Thunderstorm here in the parking lot at Cabelas in Kansas City and I think it's safer to stay in at the moment, otherwise I would go out and check

s

[drifter]

Should be written on the cap.

Watch that Kansas weather, you don't want to be squishing the wicked witch of the east with your house and then having to walk all the way to Emerald City.

[thewiz]

I had the same problem with my 6.5 turbo diesel.
The cap didn't hold pressure.
The NAPA store had lots of caps so I replaced my bad one with a new one and the NAPA guy tested it with a little pump thingy.
The pressure is stamped on my new cap.
After that the coolent stayed where it belongs.

[rvwarrior]

Yeah, the weather was pretty wild here in Kansas City last night. I'm pretty sure I saw Toto fly by my window

Hey John, good theory on the Radiator cap

I pulled mine off and visually inspected it

It definitely has some age cracks in the rubber seal and it didn't seem like it was sucking down as tight as it should

So, I went to NAPA and picked up a new cap

The old radiator cap on my 5.9 Cummins was a 13 Pound pressure cap

The new one is a 16 pound pressure cap. It fits on there nice and snug

They didn't have the ability to pressure test the cap at NAPA, so, on my drive to Omaha from Kansas on Wednesday, I will test her out and see how my coolant levels look

I'll keep you updated

Oh, wouldn't that be nice if it was just the cap, which, considering the look of the old cap, is highly possible

Stay tuned

s

[rvwarrior]

Found the problem

Two things

Water Pump was going bad - I had it replaced

And, sadly, I have a small head gasket leak

I still wish it was the radiator cap

Oh well, what are you gonna do?

Here's a question!

Off to the side, one of the diesel mechanic was telling me about a new product that is supposed to seal the head gasket leak

He forgot the name of the product, so I'm doing some research

Has anyone had any experience with products that are supposed to plug the head gasket leak?

Thanks

shad

[thewiz]

Steel Seal http://www.steelseal.com/

I was hoping I would not have to remove the head and use a new gasket.
I put it in my Toyota truck that was running on three cylinders.
It worked.
Simple to use and not too expensive.
I don't know if it would work in a diesel which has higher compression but it might be a cheaper solution.
I used it in 2002 and am still running with no problems.

[Russ Chastain]

From the Steel Seal website:

"The product can be used in both gasoline and diesel engines..."

[rvwarrior]

UPDATE:

About a month ago, I bit the bullet and went ahead and had my head gasket done on my 5.9 Cummins.

She's got 106,000 miles on er'.

The company that did the work really messed up a few things that I needed to get fixed at a Cummins Center, but overall, it probably cost me about $2000. That's because the original repair center messed up some stuff, like O rings, air leaks etc

When I spoke to Cummins, it was explained to me that for the same job at Cummins, they start at 30 billable hours, then go from there

That would have been $3000 +, and they work as slow as snails at those places, so, I would would have probably been hit with a $5000 bill with my luck.

Good news is that my coolant is staying steady and my temperature is staying exactly where it should be

Life is good - for now

shad

[rvwarrior]

Oh,

Another interesting thing

When we took the head into the shop, it was covered in rat droppings.

Yum

We blasted the head off in a high pressure water cleaning machine and it was nice and clean again.

Just to think, we were sleeping 3 or feet above rat shit for the past 2 years while traveling.

Gotta Love it

s

[thewiz]

3 or 4 feet from rat droppings? Some people that live in houses or apartments are closer then that and don't know it.