Mystery Coolant Shenanigans...

[Fire99]

Hi all,

I'm throwing this one out there as hopefully someone has experienced a similar issue..

I'm running Caterpillar 3126b engines (the HEUI oil pressure fed injector models) and one I noticed stopped its coolant expanding in the recovery tank when hot (it didn't drop.. It just stayed at the cold line) and when it cooled down it had lost some coolant from the recovery tank (not the heat exchanger header tank)

Firstly both engines have new Cat OEM radiator caps and the issue happens with both caps on this engine (and not at all on the other)
Secondly I cannot at this point see any obvious external leaks..
Thirdly I cleaned / rebuilt the heat exchanger with new seals etc and had it professionally pressure checked. No issues
Fourthly I reinstalled the HE and pressure checked the entire engine both hot and cold. Held the cap rating +1psi for an hour without issue.
Fifth, I've run the engine up to temp from cold with the radiator cap removed. No bubbles nor nasty whiffs and the water level in the chamber remained constant. It didn't drop whilst running at all.
Sixth, no white smoke from the exhaust. In fact it ran at temperature with no smoke at all..

So on running for about 30-40 mins it must be losing half a litre but where or how is a complete mystery... but every time the engine is run with the pressure cap on etc once the engine is stone cold, there has been a coolant level drop..
Any mystery solvers out there will be much appreciated.

Nick

 

[Portofino]

Air in the coolant system it needs burping and refilling/ topping up .Often takes a few bites of the cherry to completely get the level(s) .

My experience is mid engined front mounted radiator Ferrari .A real PITA doing a coolant flush .You would have had to have drained / refilled yours doing the coolers etc .

Find the bleed valve ( s) usually at the highest point .Get it warm and let air hiss out - then keep topping up when it’s safe to crack open the expansion cap(s) .Will take a few goes .

 

[ChromeDome]

Get an oil sample from each engine analyzed to see if there are any traces of coolant in the oil.

Will show as mayo on the stick only if severe, but even a small content would be an indicator.
At the same time you'll get a bunch of other findings reported

 

[Fire99]

Air in the coolant system it needs burping and refilling/ topping up .Often takes a few bites of the cherry to completely get the level(s) .

My experience is mid engined front mounted radiator Ferrari .A real PITA doing a coolant flush .You would have had to have drained / refilled yours doing the coolers etc .

Find the bleed valve ( s) usually at the highest point .Get it warm and let air hiss out - then keep topping up when it’s safe to crack open the expansion cap(s) .Will take a few goes .

Thanks.. I'll certainly give it a few more bites of the cherry but my gut feeling is the engine started loosing coolant before I had the exchanger off (it was part of the reason for the removal) so I sense the issue is still hanging around..

 

[Fire99]

Get an oil sample from each engine analyzed to see if there are any traces of coolant in the oil.

Will show as mayo on the stick only if severe, but even a small content would be an indicator.
At the same time you'll get a bunch of other findings reported

It's a good move I think. Certainly no harm getting an oil sample. The oil was only changed a couple of months ago so will be interesting to see if anything gets picked up..

 

[ChromeDome]

If run for a few hours or more the oil will have collected all sorts.

If no interesting findings the test will at least set a starting point for later samples, to show trends.

 

[Portofino]

Thanks.. I'll certainly give it a few more bites of the cherry but my gut feeling is the engine started loosing coolant before I had the exchanger off (it was part of the reason for the removal) so I sense the issue is still hanging around..

Ah .
Ok you say the coolers have been all pressure tested “ professionally “so I discounted that as the most obvious.
I know on some engines ( not sure about CAT s ? ) with age the liner sleeve seals go .
There is test kit you can get to identify any combustion gases and products there of in the remaining coolant .Compare both engines .

Things that accelerate the sleeve seals deteriorating are the incorrect type of coolant which eats away at the seals .
I know aged Cummins are particularly susceptible the K 9 derivatives .= very important the correct spec of coolant is used .

So any history if any of coolant changes / flushes etc ?
With these odd unknowns , mysterious causes , diagnosis etc go back what you ( or your tech ) have done last before the thing started and go from there .

It might be so tiny the sleeve seal compromise so no real white smoke or excess myo in oil to eye ball .

 

[Fire99]

Ah .
Ok you say the coolers have been all pressure tested “ professionally “so I discounted that as the most obvious.
I know on some engines ( not sure about CAT s ? ) with age the liner sleeve seals go .
There is test kit you can get to identify any combustion gases and products there of in the remaining coolant .Compare both engines .

Things that accelerate the sleeve seals deteriorating are the incorrect type of coolant which eats away at the seals .
I know aged Cummins are particularly susceptible the K 9 derivatives .= very important the correct spec of coolant is used .

So any history if any of coolant changes / flushes etc ?
With these odd unknowns , mysterious causes , diagnosis etc go back what you ( or your tech ) have done last before the thing started and go from there .

It might be so tiny the sleeve seal compromise so no real white smoke or excess myo in oil to eye ball .

Fortunately or unfortunately depending on circumstances, the 3126 / C7 series engines don't have liners. They're "parent bore" engines so we can rule out sleeve seals..

 

[ChromeDome]

Depending on which testing lab you use, they may also do coolant (and other liquids) analysis.
Might be an idea to include a couple of samples when you send the oils off.

Scientifically much better than visual checking.

 

[Fire99]

Depending on which testing lab you use, they may also do coolant (and other liquids) analysis.
Might be an idea to include a couple of samples when you send the oils off.

Scientifically much better than visual checking.

Thanks mate... Certainly could be an option to be 'belt n braces'...

 

[Portofino]

Fortunately or unfortunately depending on circumstances, the 3126 / C7 series engines don't have liners. They're "parent bore" engines so we can rule out sleeve seals..

But rule in porosity in the block instead in the absence of HG and leaky cooler .

What about the Charge air cooler ( CAC ) ? What have you done checking over wise with this ? CATs are well documented for leaky CAC s .
A large catastrophic leak ( which you haven’t got ) = hydrolock = bent rod .Thinking on a spectrum yours leaking a little and coolant weeping into the charge air being burnt up , but in tiny quantities so you don’t notice ……yet !

A friend got stranded in Corsica with a CAC leaky on C12 s .lost his summer .


I take the “ cooler “ referred to post #1 was the main seawater / closed cooling one ? .
You haven’t mentioned this far anything CAC wise .

 

[Fire99]

But rule in porosity in the block instead in the absence of HG and leaky cooler .

What about the Charge air cooler ( CAC ) ? What have you done checking over wise with this ? CATs are well documented for leaky CAC s .
A large catastrophic leak ( which you haven’t got ) = hydrolock = bent rod .Thinking on a spectrum yours leaking a little and coolant weeping into the charge air being burnt up , but in tiny quantities so you don’t notice ……yet !

A friend got stranded in Corsica with a CAC leaky on C12 s .lost his summer .


I take the “ cooler “ referred to post #1 was the main seawater / closed cooling one ? .
You haven’t mentioned this far anything CAC wise .

The cooler i'm talking about is the main heat exchanger. The Charge Air Cooler or 'Aftercooler' in Cat 3126b land is raw water cooled so unaffected by this little scenario.

 

[Mr Googler]

Is the calorifier on the engine in question? Worth considering

 

[Keith-i]

Just because you don’t see white smoke in the exhaust doesn’t mean you don’t have a small head gasket leak.

 

[Portofino]

Condensing all this from the info thus far from my arm chair in the absence of the history of usage from first principles.

-Air locks …….my post #1 .

-HG
- Porous block

There is one more a warped head = sits under the HG failure . Sticking with HG some manufacturers in the service regimes request re torquing up the head bolts …..usually after long time eg 10 yrs or high miles in cars or high ish hrs in marine .This is on 2200 hrs . So it’s gone past 2x 1000 hr milestones .

To the OP 1- has anyone ever had a torque wrench on the head bolts ? Should they have ? Ought to be done now to exclude ?
2- Have you had a overheat situation recently I mean before it started dropping its coolant level ?

 

[Fire99]

Is the calorifier on the engine in question? Worth considering

Thanks mate.. A good point and yep the take-off for the calorifier is on this engine but I've disconnected the hoses at the engine end to double check for any leaking past the taps. Both a fine..

 

[Fire99]

Just a little update. There's not been any overheating on this engine, well certainly not in the 2 years I've owned it and no reports prior.
The likely culprits at this stage are 1. Crack in the exhaust manifold (this isn't unknown on Cat 3126b's) as it's coolant cooled. 2. Leak in turbo coolant passage 3.Head Gasket leak - a marine engineer didn't think that likely due to the symptoms. 4. Heat exchanger despite passing the pressure tests has a leak..
I've run UV dye through the system so we shall see the outcome.

 

[westernman]

I would bet on the heat exchanger leaking coolant through to the sea water side.

I had this on my Yanmar. Just a little at first, hardly worth bothering with, then a bit more requiring a top up after each run to requiring a large amount of water each hour of running......

Needed a new heat exchanger. Which was huge bucks for a small low powered engine.

 

[Assassin]

Have you considered the fact that thermal expansion causes issues, Portofino is on the right track here with the porous block and maybe onto something with the pressure testing as this needs doing twice, once cold and onc again at running temperature as different materials expand and contract at different rates and that seal which is sealing when cold may not seal correctly when warm or hot; or run through a period where thermal expansion occurs and at a set range, leaks, then settles down once fully hot.

 

[westernman]

I would bet on the heat exchanger leaking coolant through to the sea water side.

I had this on my Yanmar. Just a little at first, hardly worth bothering with, then a bit more requiring a top up after each run to requiring a large amount of water each hour of running......

Needed a new heat exchanger. Which was huge bucks for a small low powered engine.

Pressure test the heat exchanger when it is hot inside. I.e. at 85-90C.
I.e. you need to pour boiling hot water through the fresh water side for a fair while before testing.

Engines themselves are usually very robust - except for the bits which come into contact with salt water.
Especially hot bits in contact with salt water.