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Old 08-19-2020, 06:47 AM   #1
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Cat 3208 NA coolant purge/burp vent location?

Hi folks
Can anybody let me know the location/s on a Cat 3208 natural to purge air from the coolant system?
Just completed a coolant change, and both engines shot up to 100 deg. C (212 F) once we got going on a sea trail within a few minutes.
The raw water side is fine, good flows through exhaust etc.
Being naturally aspirated, turbo is not relevant to vent of course, just any other locations.
Thanks in anticipation....
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Old 08-19-2020, 01:29 PM   #2
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I have the same engines 3208NA. It should automatically vent according to my service manual. I have not had a problem when I changed coolant last year.
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Old 08-19-2020, 04:52 PM   #3
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I have the same engines 3208NA. It should automatically vent according to my service manual. I have not had a problem when I changed coolant last year.
Cheers, Iíve got the operation and maintenance and parts manual, but clearly need the service manual.
Can you tell me what temp your water regulators work at, 176 F or 194 F?
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Old 08-19-2020, 05:43 PM   #4
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My engines are running at 185 degrees in PNW waters. I'd expect they have 180 degree regulators. The parts book shows 9L6756. That one is hard to find. Looks like 102-8392 is compatible which is a 180 degree regulator/thermostat.

Based on the description in the service manual it does not seem to vent while in operation (strange). I'd let it cool down and remove the coolant cap for a few hours. When you start it up later, leave the coolant cap off until coolant starts pushing out. That should get rid of the air.
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Old 08-19-2020, 06:05 PM   #5
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My manual says to add the coolant very slowly. Failure to do so can create an air pocket. The easiest way to remove an air pocket in the cooling system is with vacuum. Your local auto parts store should have a radiator vacuum pump.
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Old 08-19-2020, 06:46 PM   #6
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I've never had a problem burping a 3208, but all my experience is on the turbo versions.

Got a water heater on the loop? That can air load the circ pump.
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Old 08-20-2020, 03:15 AM   #7
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Thanks for your replies folks, there is a water heater looped into the port engine system, but they are both getting hot?
Iíve run the engines up to temp with the caps off as suggested, let them cool down over night, checked coolant level this morning, both where they should be (previously high, assume because of trapped air), tried again, still both went to 212 F?

The full story is Iíve just fitted the Greenwater Marine Exhaust dry riser system, with a retro raw water plumbing system. Exhaust flow is good, I followed Dave Doolings recommendations on the modified T piece etc.

Anyway, please offer any suggestions, Iím keen to get this sorted
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Old 08-20-2020, 07:07 AM   #8
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A couple of things:

Check the hoses to your coolant heated water heater. Make sure they warm up with the engine. If not, coolant is not circulating.

Where are you measuring the 100C temp? It is tricky on a 3208 to get a decent temp reading with an IR gun. Or were you reading helm coolant temp gauge? Manifolds (on a T or TA version) can run 100C with cyl heads at 85C, but gots to know where to read the heads. Not sure of the flow path on the NA version.

There should be a temp sensor on top of timing gear case just to the right and fwd of inj pump, could try burping there.
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Old 08-20-2020, 08:25 AM   #9
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Quote:
Originally Posted by Ski in NC View Post
A couple of things:

Check the hoses to your coolant heated water heater. Make sure they warm up with the engine. If not, coolant is not circulating.

Where are you measuring the 100C temp? It is tricky on a 3208 to get a decent temp reading with an IR gun. Or were you reading helm coolant temp gauge? Manifolds (on a T or TA version) can run 100C with cyl heads at 85C, but gots to know where to read the heads. Not sure of the flow path on the NA version.

There should be a temp sensor on top of timing gear case just to the right and fwd of inj pump, could try burping there.
Reading the helm temp gauge for the 100C, the engine block and manifolds are reading 80C via the IR gun.
The boat is tied at the slip running in gear at 800 rpm, as I donít want to risk an overheat going for a run.
What is the procedure for burping the system via the temp gauge sender? While the engine is running?

Appreciate the comments Ski, and also the ability to convert F to C, cheers
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Old 08-20-2020, 09:25 AM   #10
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Temp alarm switch is on top of timing gear housing as described. Gauge sender is on/near regulators on front left of tg housing. I'd try venting at temp switch, disconnect wires, unscrew and see if air comes out. Do it cool with engine off, pressure cap off.
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Old 08-20-2020, 04:34 PM   #11
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Temp alarm switch is on top of timing gear housing as described. Gauge sender is on/near regulators on front left of tg housing. I'd try venting at temp switch, disconnect wires, unscrew and see if air comes out. Do it cool with engine off, pressure cap off.
Will do, thanks
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Old 08-22-2020, 02:46 AM   #12
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Just an update, although the saga isn’t yet over. Managed to get the port engine to stay around the 85C by following Ski’s suggestion but also released a brass fitting on the thermo/water regulator housing, to drain a cupful out.
The stb engine however didn’t respond to the same treatment and shot up over 100C. I drained down half the coolant via the bottom of the heat exchanger an carefully/slowly refilled it half a litre at a time.....still no good, overheated the same.
At least I know it’s a coolant venting issue.

Any suggestions, gratefully accepted
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Old 08-22-2020, 09:45 AM   #13
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With pressure cap on and motor a little warmed up, rev up (in neut) to like 2000 for a few sec. Circ pump might eject the air in it.

Also if you can get your hands on a coolant pressure tester (most mechs have one), pump system up to like 16psi and then do the neutral rev. At 16psi any air trapped will be at half the volume and that will make it easier for pump to purge.
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Old 08-23-2020, 05:43 AM   #14
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Just want to say thanks again to all who contributed to this thread, issue has now been resolved, both engines operating around the 85C.
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Old 08-23-2020, 08:01 AM   #15
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Nice.
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Old 09-11-2020, 04:54 PM   #16
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Just when you think you have a problem sorted......

Because TF is often used as a research source for issues relating to older trawlers, in this case older marine engines, I thought it might be useful to continue with further developments in the rising engine temp saga.

As mentioned above, the IR temp gun indicated similar engine temps during a quick sea trial, although the gauges didn’t agree.
A check with the multi-meter measured 13.9 volts at the alternators, reducing to 13 at the helm panel, then 12.2 at the gauges themselves.

It appeared resistance in the electrical system was the gauge fault, a clean up of corroded pin connections, the worst were closest to alternators themselves being in the engine room, which improved the readings in volt and temp gauges.
At this stage I thought I was onto the problem, so did another sea trial a bit further, stb engine on the IR temp gun was more than 10 deg. C hotter than port?

This is the where you need to think back to everything you have recently done to the engines since they were running at normal temps.

During a recent major service, both heat exchangers were removed the stripped for an acid dip/descale, where forum advice was to change the water regulators/thermostats while the 88 lb. (40 Kg) HE’s are off the engines.
Port side was done the previous year according to records, so I ordered two new ones from Cat for the stb engine.
According to Cat (which I’ve recently found out about but didn’t know about at the time) they recommend a 97 deg. C (206 deg F) water regulator for my 3208 NA, so this is what I installed alongside the 82 deg. C (180 deg. F) on the port engine.
I’m going to change the hotter temp water regulators for the 180 F versions, a total PITA because of the monstrous weight in a tight space, but prefer to have the gauge readings similar, and in case of a genuine overheat, more warning time, also not sure about the factory temp alarm sensors and how they will cope with the higher temp.

Also mentioned previously, the original cast iron, wet exhaust risers were replaced for custom SS dry risers (Greenwater Marine Exhausts) so a lot of overheat focus has been on the new retro fitted raw water plumbing, which besides the coolant air-lock scenario was high on the list of suspects. So far though the plumbing seems fine with good raw water flows.
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Old 09-12-2020, 09:30 AM   #17
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I run the 180. Also, be SURE to get the right housing gaskets based on serial number, I had my local guy convinced he was giving me the right ones but I needed a slightly older version and my housing kept leaking, so I got to practice this job multiple times. Like 5 or 6.

But I digress, what I wanted to say is if you remove the large bolts on the heat exchanger, loosen the hose clamps, you will have just enough room to rock the heat exchanger fwd and get the housing off without having to lift the HE off. Saves time. Saves your back.
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Old 09-12-2020, 03:32 PM   #18
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I run the 180. Also, be SURE to get the right housing gaskets based on serial number, I had my local guy convinced he was giving me the right ones but I needed a slightly older version and my housing kept leaking, so I got to practice this job multiple times. Like 5 or 6.

But I digress, what I wanted to say is if you remove the large bolts on the heat exchanger, loosen the hose clamps, you will have just enough room to rock the heat exchanger fwd and get the housing off without having to lift the HE off. Saves time. Saves your back.
Thanks Ghost, appreciate the advice. Iíve heard mentioned before the moving the HE forward option, and Iíll be trying anything to make it easier, although I will have help this time.
Yes, finding a good parts interpreter at a dealership who is a logical thinker, especially prepared to go the extra mile with old marine engines, can be a bit of pot luck.
Iíve learned previously not to rely on my own parts catalogue, instead quote the serial number, but my serial number got me the hotter running regulators.
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Old 09-12-2020, 07:53 PM   #19
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Thanks Ghost, appreciate the advice. Iíve heard mentioned before the moving the HE forward option, and Iíll be trying anything to make it easier, although I will have help this time.
Yes, finding a good parts interpreter at a dealership who is a logical thinker, especially prepared to go the extra mile with old marine engines, can be a bit of pot luck.
Iíve learned previously not to rely on my own parts catalogue, instead quote the serial number, but my serial number got me the hotter running regulators.
Yeah, I was not even mad at him. It was kind of hard to read and when you held the gaskets up, they lined up. Yet somehow they would not seal. I was putting machine straight edges on it and could not measure a difference, but just know that when we got the older ones in, they sealed first time. I usually take the time to go through the parts manual and did not pick it up either, until I took a really hard second look after the first ones kept failing and found the other serial number reference. It happens.
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