gummy substance on engine following coolant flush

[OneDrop]

2000 Catalina 34mkii, Summer of '24 completed a coolant flush and change, unknown what type of coolant was used by prior owner, so flushed system 3 times with fresh water before filling with new coolant. Summer of '25, no overheating issues and coolant looks good, however we've developed a coolant colored substance all over the block, no active leaks, but seems like its coolant related.

Thoughts?

 

[dlochner]

Looks more like rust to me. If the coolant levels are as they were when you filled the system, then it isn't a coolant leak. Given its proximity to the sea water pump, I'd suspect the pump or perhaps a pump seal that is spraying sea water. Could also be a worn cover plate on the sea water pump.

 

[OneDrop]

For sure there is surface rust on there, but but there is a crystalline type pink substance at the hose ends and on some bolt heads thats new, my my concern was an interaction between old old coolant and and new. I just attached a zoomed in portion of the non-rust gunk.

 

[dlochner]

For sure there is surface rust on there, but but there is a crystalline type pink substance at the hose ends and on some bolt heads thats new, my my concern was an interaction between old old coolant and and new. I just attached a zoomed in portion of the non-rust gunk.

That can happen when different coolants are mixed. It does clean up and the flushing probably cleared most of it out.

 

[Ralph Johnstone]

2000 Catalina 34mkii, Summer of '24 completed a coolant flush and change,

Did you use a commercial flushing compound or just add three changes of water to remove the old coolant ?

The big question here is, "Did you run the engine for 20 minutes to get it hot after each of the rinse water additions to POSITIVELY ENSURE the stat had opened and every channel was thoroughly flushed with clean water before draining and repeating ?"

You've got my money on a bet that you had a reaction between the old and new coolant. And it was a doozy. See if you can collect some of the crystals on the block and test to see if they are water soluble. If they are, you're safe. Maybe get the new coolant mix out of engine as the crystals may damage your mech. seal in the water pump.

Check inside the coolant chamber and see what's doing in there. What is the brand and type of final coolant added ? Maybe remove some of the new coolant and boil it dry on a bottle lid to see what it leaves behind. More crystals ?

If there is something nasty going on in the coolant, I would get it out of there and consider looking at a commercial block cleaner which will handle the job. Check with the mfg. for their ideas.

I guess that's why coolant manufacturers always say to avoid mixing different types of coolant. Live and learn.

 

[OneDrop]

Appreciate the feedback, I did run the engine between flushes but in retrospect I couldnt guarantee it got up to full temp. looks like i know what my April project is! luckily no overheating issues this past summer, but a commercial flush will be first on the list. My primary concern ofcourse is how is it getting out of the engine?

 

[kappykaplan]

My primary concern of course is how is it getting out of the engine?

If everything else is ruled out, it must be a leak!

 

[Stu Jackson]

Ralph's post #5 and Kappy's #7 nailed it. What was in there should not have been pink, nor should what you used as a replacement for your M35 engine. It should be green. My first thought was a leak at the top clamp on the black hose underneath the coolant pump. That hose can replaced by a much less expensive Toyota hose (1" to 7/8"). You can find it on our C34 forum:

Engine Coolant Pump Hose 101 - Toyota Part instead of Universal Pricing - the BLACK curvy one under the pump 1" to 7/8"
M25 and M25XP Freshwater Coolant Hose 1" to 7/8" TOYOTA Source

 

[OneDrop]

Thank you all for your help!

 

[OneDrop]

FyI I used Shell Rotella ELC 50/50, I don't remember where I read that that was the preferred antifreeze when researching the project

 

[thinwater]

[Decades formulating and even inventing (one patent) engine coolants.]

With three changes it is very unlikely that Rotella ELC reacted with what was left in a meaningful way. It is also likely that it has been a LONG time since it was changed. What is likely is that the organic acid in the ELC was unkind to old hoses and cause them to seep at the ends. The leaks can be very small and only occur at specific temperatures or under load. I'm thinking new hoses and clamps. Clean up the barbs very carefully.

Given the red rust, I would also say that there is either ...

• An air suction leak resulting in oxygenated coolant, which is very corrosive. If this is the case, the oxygen also oxidized the glycol to glycolate and the pH is probably quite low, perhps below 7. Check it. Or ...
• The heat exchanger has a small leak and you are getting seawater into the coolant. It only takes a few percent to cause a lot of corrosion in a non-seawater engine.

Combined with the leakage, I'm guessing the coolant has oxygen in it and has a low pH. Simple to test. Common problem, often mistakenly blamed on the coolant.

 

[OneDrop]

Given the above, at this point, when I go and drain, replace hoses (just purchased full Westerbeke kit), check/clean/replace the HX, should I re-flush and swap back to the old style coolant, or is the Rotella ELC ok at this point?

 

[dLj]

No need to flush or change. If you want to change antifreeze - then you would do a flush. But you can stick with the one you are running now. It's a good one.

dj

 

[thinwater]

Given the above, at this point, when I go and drain, replace hoses (just purchased full Westerbeke kit), check/clean/replace the HX, should I re-flush and swap back to the old style coolant, or is the Rotella ELC ok at this point?

Rotella is good and by now you have flushed all you need.

BTW, the coolant engineering departments (off the record) fear flushing chemicals, particularly in the hands of DIYs. They are corrosive and not always well removed (not easily well removed!). I would ONLY using flushing chemicals if there were blockages or serious lime build-up, which there should never be. Never use tap water, only distilled.

My guess is that you have intermittent leaks around the hoses. Long life coolants use organic dibasic carboxylic acids (sort of like a soap) as their primary corrosion inhibitors, and not all of the older hose formulations were completely comparable. Traditional coolants were almost entirely inorganic. Sort of like the switch to e10 gasoline.

The long life coolants really are good products. With diesel engines they are much better at preventing cavitation pitting on the cylinder liners, and they are kinder to pump seals (the primary reason they were introduced--silicate grinds up seals). But there can be some change-over trauma.

 

[Johnb]

After reading this thread I got curious about testing the coolant. I read that it can be done with a voltmeter (or multimeter in volt measuring mode), and you should replace it, according to different websites, if:
The voltage measured is greater than 4 volts
The voltage measured is greater than 0.4 volts
The voltage measured is greater than 40 millivolts
The voltage measured is greater than 4 millivolts
I also read it should be measured with the positive probe in the liquid, and with the negative probe in the liquid.

I also read that ph measuring test strips are a good way to go - accompanied by variations on what the upper limit of ph should be.

@thinwater - any comments?

 

[dLj]

After reading this thread I got curious about testing the coolant. I read that it can be done with a voltmeter (or multimeter in volt measuring mode), and you should replace it, according to different websites, if:
The voltage measured is greater than 4 volts
The voltage measured is greater than 0.4 volts
The voltage measured is greater than 40 millivolts
The voltage measured is greater than 4 millivolts
I also read it should be measured with the positive probe in the liquid, and with the negative probe in the liquid.

I also read that ph measuring test strips are a good way to go - accompanied by variations on what the upper limit of ph should be.

@thinwater - any comments?

With all due respect - measuring voltage with both probes in the coolant has got to be internet hocus pocus....

When I used to check large systems with anti freeze, I used a pH meter and a diffractometer. But really, that was only done on really large systems where the cost of testing was insignificant to the cost of changing out the coolant (I'm talking thousands of gallons). The antifreeze in a recreational boat engine does not warrant this kind of testing. Just change the fluid if you think it needs it. It does not need to be done often. It's not like oil changes. As long as you have no leaks in your system it lasts quite a long time...

dj

p.s. Here's actually a nice blurb from Hagerty that pretty good.

 

[Davidasailor26]

After reading this thread I got curious about testing the coolant. I read that it can be done with a voltmeter (or multimeter in volt measuring mode), and you should replace it, according to different websites, if:
The voltage measured is greater than 4 volts
The voltage measured is greater than 0.4 volts
The voltage measured is greater than 40 millivolts
The voltage measured is greater than 4 millivolts
I also read it should be measured with the positive probe in the liquid, and with the negative probe in the liquid.

I also read that ph measuring test strips are a good way to go - accompanied by variations on what the upper limit of ph should be.

@thinwater - any comments?

I’m with dj - that doesn’t sound legit at all. The coolant is mostly just ethylene glycol in water. There’s nothing there to create a voltage potential at all.

 

[dlochner]

If you want to check the antifreeze, use a refractometer to see the glycol to water ratio. About $20 from Amazon.

 

[Johnb]

I’m with dj - that doesn’t sound legit at all. The coolant is mostly just ethylene glycol in water. There’s nothing there to create a voltage potential at all.

The measurement is taken between the engine block and the coolant, sorry about the typo.

I'm guessing that as the coolant deteriorates and the ph rises it becomes more alkaline and this causes a potential difference between the coolant itself and the metal of the engine. I was wondering if @thinwater could explain.

Also ph test strips are actually very cheap and that is a really quick test.

 

[Johnb]

If you want to check the antifreeze, use a refractometer to see the glycol to water ratio. About $20 from Amazon.

Curious minds just want to know why/if the voltage test works.