# Could a water pump cause low flow to my heater? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** charger, dodge\ **Created:** [December 22, 2017, 3:16am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546 "2017-12-22T03:16:19Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 3:16am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/1 "2017-12-22T03:16:19Z")
I have flushed the entire coolant system. I replaced the oil cooler (it is in line with the heater core). I seem to have enough flow thru the heater core. The heat is good if I run the RPM up to 3K. Could the impelars on the pump rust out or get clogged? I have heard of this before but didn’t believe it. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [December 22, 2017, 3:21am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/2 "2017-12-22T03:21:45Z")
> [@olemike](#): > > Could the impelars on the pump rust out or get clogged? Generally the impellers erode away to where they no longer move sufficient fluid. But that generally manifests itself as an engine running too hot. How did you determine that you have sufficient flow through the heater core? Is the engine reaching full operating temperature? Normally, or barely? Do you live above the 45th parallel? ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [December 22, 2017, 3:28am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/3 "2017-12-22T03:28:07Z")
Are you certain the cooling system is full? I have been able to add 2-3 quarts after a road test with these cars. As I recall the 3.5 L engine has the oil cooler problem, is that the engine you have? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 22, 2017, 3:31am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/4 "2017-12-22T03:31:04Z")
What I’d check if I had that problem - Low coolant - Air in coolant - HVAC door(s) problem - Heater core needs flushing or replacement - Faulty thermostat - Faulty water pump Have you removed the outlet of the heater core with the engine running and measure the flow rate through it? Have you measured the temperature of the coolant? Yes, the pump’s impellers can gradually erode away, even to nothing. As posted above, that usually shows up as engine overheating first. But it could show up as an hvac heating problem too I suppose. ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 3:32am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/5 "2017-12-22T03:32:13Z")
I put a scanner on and the engine temp got to temp at a good rate. It also stayed at 190° +/- 5° . Mechanic who flushed it said he had good flow to the heater. I have flushed water thru it myself after he did and flow seems OK. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 22, 2017, 3:33am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/6 "2017-12-22T03:33:59Z")
> [@olemike](#): > > I have flushed water thru it myself after he did and flow seems OK. Was the water pump driving the flushing action? Or were you using a garden hose? ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 3:34am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/7 "2017-12-22T03:34:29Z")
yes I have the 3.5. I have filled the expansion tank. and bled out the air. Again the heat is good if I rev it up to 3K ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 3:34am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/8 "2017-12-22T03:34:54Z")
garden hose. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 22, 2017, 3:37am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/9 "2017-12-22T03:37:04Z")
> [@olemike](#): > > garden hose. Ah, well you could still have a faulty water pump then, or some obstruction prior to the heater core. Can you come up with a method to test the water pump flow? On my Corolla I can remove the top hose on the radiator, direct the flow into a bucket, and watch how much water comes out as the engine heats up. It really pours out , quite a large volume flow. ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 3:38am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/10 "2017-12-22T03:38:50Z")
To replace the heater core will cost $1,000. Too old to do it myself - my body just can’t bend that much to replace the heater core. Now I can replace the water pump myself. Just have doubts about the water pump being the problem. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 22, 2017, 3:43am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/11 "2017-12-22T03:43:21Z")
hmmm … well probably next step is to measure the flow rate of coolant flowing through the heater core at warm idle, and its temperature. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [December 22, 2017, 4:58am UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/12 "2017-12-22T04:58:45Z")
Water pump impellers are generally made of stainless steel or plastic, I don’t recall which this one is made of but impeller failure is unlikely. Did you loosen the bleed valve on the water outlet while adding coolant? Keep adding coolant until the level is 1/2" from the top of the reservoir. ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 22, 2017, 9:35pm UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/13 "2017-12-22T21:35:39Z")
Yea, I find it hard to believe the impellers would wear/rust out. I’ll keep the reservoir full and see if that helps. Thank you and merry Christmas. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 22, 2017, 11:34pm UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/14 "2017-12-22T23:34:16Z")
[https://www.gatestechzone.com/en/problem-diagnosis/cooling-system/water-pump-failure-signs](https://www.gatestechzone.com/en/problem-diagnosis/cooling-system/water-pump-failure-signs) ---
**Author:** ![olemike](https://avatars.discourse-cdn.com/v4/letter/o/76d3ee/32.png) [@olemike](https://community.cartalk.com/u/olemike)\ **Post date:** [December 24, 2017, 1:38pm UTC](https://community.cartalk.com/t/could-a-water-pump-cause-low-flow-to-my-heater/110546/15 "2017-12-24T13:38:33Z")
One thing I haven’t looked at yet is the drive belt. I get good heat at 3000 rpm - if I have some slippage from the belt that is why at low rpm I don’t have heat.