[Mike]

Bill, after removing and rodding out the heat exchanger, and installing the new 160 T-stat, the issue seems to be resolved
Its running at about 176-178 degrees on cruis at 2100 RPM and cools down to about 160 when I back down to idle speeds.
I believe the exchanger has a lot of “scum” built up because when I filled it with a 50-50 mix of acid and water, it changed the tube co;or from grayish to copper and I did this 2 times for about 20 minutes each time.
I also had the expansion tank repaired at a local radiator shop, who boiled it overnite in acid and then soldered or welded up the bad areas, and it pressure tested to 20 lbs.
I have 2 offshore trips in the last 3 weeks (30 miles each way) and it preformed great. Although it did loose about 2 quarts of coolant after the 1st trip, may have been low on the initial fill, not sure as I just returned Saturday and have yet to check my fluid levels

[Mike]

Yes sir I shot temps with IR temp gun and it matched my gauge

[Mike]

today I pulled the heat exchanger and flushed it with a 50/50 mix of water and muratic acid.
salt side brightend up the copper tubes and
I got a little grey-ish washout
about a 10 minute soak
freshwater side I capped one end and gave it a 5 minute soak of same 50 50 and rodded it out after soak
able to reach all rod tubes except outside diameter tube access blocked by housing. then flushed with fresh water. washed out with a blackish residue but flushed out clean. then flushed the block with fresh water. the Tstat and housing are off flush out was clean,
Boiled tstat and it opened at 180 degrees, there was some saltish or calcium ish buildup on the stat shaft
Awaiting my 160 degree tstats should be here in the next few days
So All is flushed out and ready to re-assemble
Is the water pump an issue here

note the heat exchager gged them up from dissolving.

[Mike]

Tony
I know your a busy man,
but,I did reply to your questions above on the temperatures at speed.
Thanks again Mike in Texas

[Mike]

Tony, cruise at 2050 rpm im reading 190 If I stay on it for over 20 minutes it stars to creep up to 195 so I have to lower my RPMs down to 1900 to be comfortable in the 185 range. when I back it down to idle it comes down to 180
I did order your 160 degree tstats over the weekend hoping for lower running speed temp.
IR gun confirms these temps
Thanks Mike

[Mike]

any one have some info in this? I will break down the heat exchanger if needed, just want to eliminate any other possibility first

[Mike]

Tony, if you see this
Can you show me in pics or words how the plumbing of a remote expansion tank would be fitted to this 1987 6BT
Your earlier reply was greatly appreciated
Mike

[Mike]

I see some info on forum about reworking cooling system by retrofit new expansion tanks
Can this be done or if not, where do I find new replacement tanks

[Author]

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