Cat 3508 JW pressure issues

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blackhatch
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Cat 3508 JW pressure issues

Post by blackhatch »

Just had 2 3508's rebuilt by Cat. Both engines are boiling over when they are being shut down. The caps are brand new 7PSI from Cat. Jacket water temp is 195 when running. Cat has changed the caps to 14psi and said not to worry this is normal.
Anybody else got any experience of this, and doesn't such a big jump in Cap size seem a little extreme?

Thanks

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Merlyn
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Re: Cat 3508 JW pressure issues

Post by Merlyn »

I reckon it's yet again another case for the pressure tester on the header tank ( and for testing the correct cap lift psi ) together with the temp. Ray gun temp. measuring device.
Again like the Volvo write up re shut down over pressuring the coolant system seems a bit weird it's had a rebuild and done by the same firm?
Identical happenings yet again.
Needs isolating as to whether the cap lifting is down to excessive pressure or an overheat situation.
Clip the pressure testing machine onto the header tank and run the engine to observe running pressures on/ off load and in particular during shutdown to see if the lift/ excessive pressure only occurs during shutdown.
Seems maybe a localized overheat situation causing the expansion and only when the water is not circulating via the water pump etc side of things.
Measuring with the temp. Ray gun ( aligning the dots before pulling the trigger to get the reading ) either side of the Stat. might prove interesting.
Also any blockages/restrictions in the coolant system will easily show up when tested all over the coolant system flow and return including intercoolers/ heat exchangers etc.
If it was all ok before the overhaul then obviously the work done has caused the problem.
Again same person who did both engines and again exactly what was done?
Piston / liner / head etc or what?
New Stats. fitted?
Pretty common and proven engine and I have seen them with 13 psi caps fitted as standard although I would consider your doubling up from the original 7 to 14 is just a quick shut you up quick jobby without really getting to the root of the manufacted problem.
If you don't have any test kit I don't really see how you can satisfactorily tackle the problem except by the substitution method of changing Stats. etc which must be very frustrating indeed.
Best of luck and do let us know the outcome.
( or run on forever with the 14 psi caps on ?)
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

1moley
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Re: Cat 3508 JW pressure issues

Post by 1moley »

Have you tried when the unit is running to crack the bleeds around the engine to see if any air is present?

Is it possible to observe water level any rise or fall in header tank during running?

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JK
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Re: Cat 3508 JW pressure issues

Post by JK »

How long is the rundown after coming off load? Is it possible the cooling water stops circulating and flashes off at the liner surface? Also have you checked the vent to the expansion tank? Is it common and does it have a hose that may have collapsed inside?

blackhatch
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Re: Cat 3508 JW pressure issues

Post by blackhatch »

OK, thanks for all the input. It would appear that Cat put 197deg thermostats in these Engines, prior to rebuild it is speculated that we had 187deg. the Engines don't get hot enough to actually open the thermostats fully, this little to no water is coming from the coolers. this is creating a high temp in the expansion tank, causing boil over when shut down.

New 187deg thermostat installed and all is well again.

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Merlyn
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Re: Cat 3508 JW pressure issues

Post by Merlyn »

Interesting one.
Wonder why the temp. operating range change?
Reckon the infra red ray gun for measuring temps. each side of the stat may well have spotted that one?
Cheap as chips to buy and I find it invaluable for tracing faults such as this.
Nice and easy to use, in writing it's also nice to see the problem solved and furthermore the answer published on the site.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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JK
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Re: Cat 3508 JW pressure issues

Post by JK »

This is interesting.
When we bring in a OEM FSR we make the fatal assumption that everything is going to be good after the fact.
We had a Cat that failed to start and when it ran down to stop,the control system restarted it at the exact instant that it kicked in the opposite direction and it started and ran in the reverse direction. Don't you wish you had bought a ticket then? It did a significant amount of damage and when it was rebuilt under warranty because it had been overhauled just before, it was found to have a bottom end installed backwards. It was on limited lifespan even without the restart problem.

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Merlyn
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Re: Cat 3508 JW pressure issues

Post by Merlyn »

Wonder what model engine that was JK?
Pre CR I bet?
Was the rod fitted the wrong way round or did the design of that particular engine not allow the bottom cap to be fitted ass about face?
Splined that is.
IE was the oil hole in the top part of the rod not facing the camshaft.
Still dont understand why it ran the other way though?
Thinking caps on for JK methinks here
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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JK
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Re: Cat 3508 JW pressure issues

Post by JK »

3408.
The engine failed to start and started to wind down. Do you remember how at the very last instance the flywheel gives that kick back in the other direction before everything comes to a stop? It seems at that instant the engine got a start command and restarted. It was all very strange and the engine had to be stripped down as the LO pump wasn't reversible. There was a bearing cap on backwards. whether the ships engineers got in there and had a look I can't remember. I got the call on the weekend from a very distressed Chief Engineer who was trying to get everything ready to sail to dock.

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