Coolant not flowing to heater core/heater does not work?

Tiny
EXTRABAD8
  • MEMBER
  • 2007 CHRYSLER 300
  • 3.5L
  • V6
  • 2WD
  • AUTOMATIC
  • 76,000 MILES
The heater has been giving me issues for a while now. At first the heater wouldn’t put out heat unless driving down the road. Now it doesn’t work at all. A/C and blower and blend door work fine. I thought it was a clogged heater core because one line was warm and the other cold. I pulled both lines, and the heater core wasn’t clogged at all. Water flowed through easily both ways. Then I put a jumper hose connecting both heater core hoses and no coolant is flowing through. I also changed the thermostat and bled all of the air out of the system. Still has no coolant flow through those heater core lines. The engine runs great, no overheating and upper and lower radiator hoses get hot.
Tuesday, December 20th, 2022 AT 11:55 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,097 POSTS
Hi,

I have a feeling the oil cooler is plugged and preventing coolant flow to the heater core.

Engine coolant flows into the oil cooler from the heater return tube and exits into the water inlet tube. If the cooler is clogged (I've seen it before) coolant can't flow through the heater core.

I attached a pic below showing the cooler. It is right near the oil filter. In the pic, the number 3 points at the filter.

Let me know what you find.

Joe

See pic below.
Image (Click to make bigger)
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Wednesday, December 21st, 2022 AT 9:22 PM
Tiny
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I think you are right. I pulled both lines off of the oil cooler and put a piece of tubing connecting the two lines and started the car and the heat worked perfectly. I ordered a new oil cooler, and it should be here tomorrow. I’ll let you know.
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Thursday, December 22nd, 2022 AT 12:29 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,097 POSTS
Hi,

That is the problem. I've seen a few but the issue seems to be becoming more common.

Let me know if that takes care of the problem.

Take care and I hope you have a great Christmas.

Joe
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Thursday, December 22nd, 2022 AT 9:32 PM
Tiny
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  • MEMBER
  • 8 POSTS
Well, I found the issue. The oil cooler wasn’t allowing any coolant to flow through it. I replaced the oil cooler and now it works like brand new, and the engine runs cooler as well. Thanks for the help.
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Thursday, January 5th, 2023 AT 8:09 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,097 POSTS
Hi,

Thank you for the update. I had a feeling that was the problem. I'm just glad to know you got it fixed.

Feel free to come back anytime in the future if you have questions or need help. You are always welcome.

Take care and I hope you have a great 2023.

Joe
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Thursday, January 5th, 2023 AT 9:05 PM
Tiny
DEEPAK WALIA
  • MEMBER
  • 2 POSTS
Resurrecting an old thread. I am currently having this issue with my son's 2009 300 touring. I wanted to know that if I unhook the pipe and bypass the cooler, do I first have to drain the cooling system? I don't want to unhook the pipe and have the entire contents of the cooling system spill out.

Thanks.
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Tuesday, January 7th, 2025 AT 7:25 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,453 POSTS
Yes it is best if you drain the coolant out before working with the heater hoses. Upload images or short video if you have any problems so we can better help you.
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Thursday, January 9th, 2025 AT 10:29 AM

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