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I have a bxs cat c15 which has psi in coolant res under load.

I have replaced air...
I have a bxs cat c15 which has psi in coolant res under load. I have replaced air compressor, water pump, thermostats, some hoses. Psi checked the system and dose not leak down. My drivers aids it has not overheated.
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Answered in 7 minutes by:
6/17/2015
Technician: Cat Man, Cat Engine Expert replied 7 years ago
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
Hi. Thanks for asking your question and requesting me. I will try and help you out.
There are three additional things I have seen cause psi in the cooling system under load.
The first and most common is a cracked pre cooler. It's located between the turbos and air to air cooler. When they get a small crack. Boost pressure will enter the cooling system under heavy load.
Second is a faulty coolant diverter valve assembly. Basically a bad diaphram. Over time the diaphram gets worn and begins to pulse. This can cause coolant to be pushed out. Normally when this is bad. Coolant is pushed out all the time. Not just under load.
Lastly is a leaking head gasket. Many times when they first fail, they put psi in the cooling system under load.
I would start with the precooler. I see these cause this problem a lot.
Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 7 years ago
Would you see any coolant in the per cooler with a psi check
Technician: Cat Man, Cat Engine Expert replied 7 years ago
Yes sometimes you will but not always. If the crack is very small it may not show. But it's worth pressure testing to see.
Also. If the crack is large enough. You could see a white residue in the precooler.
Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 7 years ago
The truck is a frieghtlinner with over a 1 millon mile. I know the rod bearings, main bearing, and oil pump has been placed. Runs like a top, no smoke or coolant leaks. Where should I start?
Technician: Cat Man, Cat Engine Expert replied 7 years ago
Thanks for the information.
I would pressure test the cooling system and see if coolant leaks into the precooler. Or you can just remove the piping around the cooler and look for white coolant residue. That's what coolant looks like when its dried in a hot area. If you see white. I would replace the pre cooler.
Let me know if you need more help.
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Customer reply replied 7 years ago
Thank you for your help. I will start thier
Technician: Cat Man, Cat Engine Expert replied 7 years ago
You are very welcome my friend. I am happy I could help.
This question will stay open for weeks after leaving a positive rating. So if you need more help. I'll be here to assist.
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
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Technician: Cat Man, Cat Engine Expert replied 7 years ago
Thank you very much for the positive rating and bonus. I really appreciate it.
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