Crud in the heat exchanger!

I drained the heat exchangers in twin 5.7 Volvo OSxi engines. When I removed the plug anodes, the zincs were gone and the holes had crud in them... I got this stuff out, but how can you tell if there is more junk insude?

Re: Crud in the heat exchanger!

Remove the end cap (plate) from the end of the heat exchanger.

A picture would really help. Have no idea if you have OEM heat exchanger or not or what model you have 5.7OSxi is only PART of the model number.

Re: Crud in the heat exchanger!

tkrfxr said:

...... I got this stuff out, but how can you tell if there is more junk insude?

Click to expand...

I have a 4" Mercruiser heat exchanger and encountered the same 'crud'.

Remove the end-caps and take a look inside the tubes.
Remove the coolant hoses and look around/between the tubes.

Don't be surprised to find sand and/or remains of long ago destroyed pump impeller pieces.

Though it may be unorthodox, I removed the exchanger to the shop, first filled the seawater side with H2SO4, drained and re-treated several times, each time removing 'crud'. Then I treated the coolant side the same, though one flush was sufficent. Afterwards I repeatily rinsed both sides to remove any residue. IF you follow this procedure..be extremely careful. This stuff will eat the skin off your bones!!! It is available wherever professional plumbing supplies are sold. About $10 per 32oz.
After I cleaned my cooler, a slight over-heating problem vanished.
FWIW....Ed in 'ol Virginny

Re: Crud in the heat exchanger!

Here are my zincs...

and here is one of the heat exchangers...

Re: Crud in the heat exchanger!

Don S said:

Remove the end cap (plate) from the end of the heat exchanger.

Click to expand...

I remover both end bolts and the ends don't come off!

They appear fused to the rubber...The crud comes out by shaking and fragmenting with an instrument. Looks like zinc and Nutra-salt sediments!

Re: Crud in the heat exchanger!

It's just stuck from paint and a bit of corrosion, use a knife, or a screwdriver and pop it off. Clean the old anode out, replace the end cap rubber gasket and you are done.

Re: Crud in the heat exchanger!

EddiePetty said:

Though it may be unorthodox, I removed the exchanger to the shop, first filled the seawater side with H2SO4, drained and re-treated several times, each time removing 'crud'. Then I treated the coolant side the same, though one flush was sufficent. Afterwards I repeatily rinsed both sides to remove any residue. IF you follow this procedure..be extremely careful. This stuff will eat the skin off your bones!!! It is available wherever professional plumbing supplies are sold. About $10 per 32oz.
After I cleaned my cooler, a slight over-heating problem vanished.
FWIW....Ed in 'ol Virginny

Click to expand...

Sulfuric Acid is a bit extreme...(and effective)...

I'm still trying to pry the end caps off without damaging the thing...

Re: Crud in the heat exchanger!

tkrfxr said:

Sulfuric Acid is a bit extreme...(and effective)...

I'm still trying to pry the end caps off without damaging the thing...

Click to expand...

True and double true.

After I cleaned my cooler, the tubes, internal and external, were spotless...looked brand new. Hey, this stuff is used to clear plumbing all the time. I did a low pressure air test just to check myself though.
And, as Don says, slip a blade of some discription around the parting joint and the end caps will pop off. Most likely you will have to renew the gaskets: I did.
Ed, again

Re: Crud in the heat exchanger!

Don's right- you've gotta get the end caps off. Maybe a rubber mallet or some gentle heat.

When I cleaned my heat exchangers, I found the CLR-type stuff Home Depot sells did a fantastic job. I also 'rodded out' the tubes with a stiff wire. I simply used 2- 5 gallon buckets and poured the stuff thru the HE into the other bucket.
Did this about 3- 4 times and they were sparkling inside.

Oh, and don't forget to buy new gaskets and anodes.

Re: Crud in the heat exchanger!

Don't make a big project out of the end cap. Stick a thin screwdriver between the seal and the end cap and give it a few taps with anything, even you hand. They aren's stuck that hard and they do stick, but it doesn't stick hard enough to damage the metal. The rubber gives up first.

Re: Crud in the heat exchanger!

Don S said:

Don't make a big project out of the end cap. Stick a thin screwdriver between the seal and the end cap and give it a few taps with anything, even you hand. They aren's stuck that hard and they do stick, but it doesn't stick hard enough to damage the metal. The rubber gives up first.

Click to expand...

Ha! The rubber gave up and the thing is open...

Thanks for the responses...The stuff inside doesn't look too bad...

I'll rinse it out and replace the rubber gaskets and anodes...

Will be ready for spring...