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markcm2
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Joined: September 02, 2015
Posts: 505
Location: Bellingham, Washington
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 Posted: Wed Mar 14, 2018 10:27 pm Post subject: Help diagnose no coolant flow through front heater core |
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We just had the engine out on a 2002 EV weekender, replaced the water pump and thermostat while it was out and now there's no heat up front but normal heat in the rear. The heat worked fine before we started engine pull.
We also replaced the front heater core. After many attempts burping the system we still only have minimal heat up front when the van is working and at full temp , nothing at idle. The back heater core is hot at all times. There is hot coolant on the inlet side of the heater core but next to no flow and the outlet side is much cooler.
We've double checked the plumbing by comparing it to another EV of the same vintage.
We have a vacuum filler and have filled and dumped the cooling system several times. The system holds a vacuum as well.
Eventually we discovered the heater control valve diaphragm was damaged so it never actuated (drew in to closed position). Not knowing how the valve worked, we took it out and put in a bypass but then realized the valve closes when under vacuum (actuated) so this really didn't make any change. So we grabbed some pliers and clamped off the hose in this loop where the control valve goes but it made no difference either.
So our assumptions are:
*The new water pump and tstat are working based on good heat in the rear of the van and normal engine coolant temperatures when monitored on OBD2
* Heater core is not plugged because its brand new Febi and we have disconnected and did a basic flow test, fluid passes freely.
Reading on the rialta forum I saw that the secondary electric coolant pump is supposed to run when the engine is hot and this function assists in clearing any air pockets in the head. We havent tested this pump yet to see if it is running.
We are getting a new heat control valve but since clamping the hose off with pliers didn't produce any flow in through the heater core I'm not sure if that will resolve the issue.
What the heck? Any ideas to help us figure out why there's not coolant flowing trough this new heater core with new water pump and new tstat? |
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Joshwa
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Joined: November 18, 2015
Posts: 810
Location: North Seattle WA
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markcm2
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Joined: September 02, 2015
Posts: 505
Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 6:46 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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The inlet side gets hot but the outlet side is much cooler, it’s as if there is backpressure on the outlet side.
If you hold both sides of the front heater core and squeeze one side in a pulsing motion you can feel the fluid freely moving through the core and pulsing on the other side as well. |
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Joshwa
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Joined: November 18, 2015
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Location: North Seattle WA
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markcm2
Samba Member
Joined: September 02, 2015
Posts: 505
Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 8:09 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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The coolant reservoir is lower than the bleeder on the heater core, a design I cannot understand. When we purge the system, we lift the bottle as high as possible.
We've tried everything imaginable, including installing a section of clear hose at the heater core so we can see the fluid. I don't think this is a heater core issue at all, but rather something in the system we are missing.
Everything in the heating/cooling system seems to be performing as expected the exception of proper flow through the front heater core circuit. We opened the heater core outlet when the engine was warm (not hot) and running, it seemed as though there was minor flow in the reverse direction, toward the heater core outlet (the passenger side tube).
We will check the operation of this electric assist pump. I thought that was only an "after run" pump but reading more it seems this pump is supposed to also run when the engine is hot and running. It is also said to prevent air pockets from trapping in the head. I have a hard time imagining how we have air in the head after pulling a vacuum on it several times but...???
We will also be replacing the faulty heater valve today. I thought for sure we found the issue with the bad heater valve but when we crimped that circuit with pliers it made no difference at all.
The water pump and tstat are both OE products and new. I've seen defective new tstats before but the heat is correct in the system and the rear heater core is good and hot so we are assuming there is no issue with the tstat or mechanical water pump. |
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Joshwa
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Joined: November 18, 2015
Posts: 810
Location: North Seattle WA
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| Posted: Thu Mar 15, 2018 9:23 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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| markcm2 wrote: |
| I thought that was only an "after run" pump but reading more it seems this pump is supposed to also run when the engine is hot and running. It is also said to prevent air pockets from trapping in the head. I have a hard time imagining how we have air in the head after pulling a vacuum on it several times but...??? |
I looked at the wiring for the after run pump and you are right. With no key in, it is always powered, but will operate only when the temperature sensor for it reaches the too hot threshold. Also, it gets direct power, bypassing that sensor via relay, with the key on. Its diagram 72/10 if you have the bently. So do you hear it run with key on? Personally, i don't think it will make a difference since it is pulling from the upper radiator hose.
| markcm2 wrote: |
We will also be replacing the faulty heater valve today. I thought for sure we found the issue with the bad heater valve but when we crimped that circuit with pliers it made no difference at all. |
Is this the shutoff valve on rear heater coolant return circuit? I think closing this should cause more pressure towards the front heater core, but seems something else is wrong. This shutoff normally closes when the AC is turned on, and might be a variable shutoff for the temperature control.
| markcm2 wrote: |
The water pump and tstat are both OE products and new. I've seen defective new tstats before but the heat is correct in the system and the rear heater core is good and hot so we are assuming there is no issue with the tstat or mechanical water pump. |
I don't think the water pump is bad with rear heater getting hot. If your van isn't overheating then the tstat is fine. I thought the heater core returns bypassed the tstat as well.
Have you tried plumbing your clear hose between the in and out of the hoses that go to the new front core? If you see and feel good flow, then you can rule out your plumbing since it all seems to be working with the exception of the flow through that core.
_________________
93 Weekender TDI conversion (AHU)
93 MV TDI conversion (1Z)
Weekender rear cot
Late model cabin air filter on 93
Euro spec bumper install on 93 |
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markcm2
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Joined: September 02, 2015
Posts: 505
Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 9:38 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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Thanks for the info on the aux water pump.
We aren't exactly sure what the heater valve does, it looks like is connected to the front heater core outlet. It defaults open with no vacuum and closes under vacuum. What we do know is the diaphragm in this one is failed so the coolant valve is always open. We checked my van which is working correctly; with a warm engine the valve closed as soon as we started the engine. We tried turning the rear heat on/off and it made no difference, the valve stayed closed and I had heat front and rear.
We did put the clear line on the front heater core, we can see it fill but cannot really tell if fluid is moving. Based on the fact that its hot on the inlet side and much cooler on the outlet side I'm inclined to say there isn't much flow through the core. If we rev the engine or drive it hard, the outlet side warms some, just like a bad water pump symptom but again, we have heat in the rear and proper cooling and a new metal water pump.
I'm inclined to look closer at all the temp sensors too. We have a "normal" reading on the dash and OBD2 but... with multiple sensors maybe one is giving a bad value. |
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Joshwa
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Location: North Seattle WA
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Joshwa
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Location: North Seattle WA
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markcm2
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Joined: September 02, 2015
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Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 10:35 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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| Joshwa wrote: |
| I would go back and test the new core again outside of the coolant circuit. To me, it seems like some debris could have gotten in there to block the flow. especially if the coolant is hot up to the core. I'm wondering if flowing some water through the core backward, would blow something out. |
We've checked the new core a few times.
I'm looking at the circuit diagrams now trying to trace things out. It looks ridiculously complicated with 3 potential valves that could be causing the issue.
It looks like both heater cores are fed in parallel, directly from waterpump, through the block and head and to the cores as seen in this first image
Then the return circuit shown in red again, plus the blue which shows the transmission cooler circuit. We have removed the OE transmission oil/water cooler and installed an external oil/air transmission cooler so this blue circuit is just water piping; it seems like we should just block that off.
Now looking at this, we need to figure out exactly what and where valves #2,#4, and # 16 are. I'm only aware of two valves, the heater valve located down in front by the auxiliary water pump and the unidentified valve under the electric solenoid which operates the heater valve and is located under the brake booster. I'm assuming #4 is the heater control valve located in the lower front by the aux pump; we know that is failed and stuck open but it doesn't appear to be in the heater core circuit. I see how this valve could affect the rate of the total cooling system but we are not having an issue with building heat, we are having an issue getting it through the front heater core. So after we replace valve #4 this leaves us looking at valves #2 and #16, the aux pump (which I would think would also affect the rear heat), and temperature sensors. |
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markcm2
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Joined: September 02, 2015
Posts: 505
Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 10:38 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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| Joshwa wrote: |
| Talked to a friend that had a similar issue and he said he remove the core exit hose and some air bubbled out and was fine after. So in his case he had a pocket of air that wouldn't move easily. So there's that also. |
Good tip for sure, I've battled that many times. At this point, we have cracked the heater core lines with the surge tank elevated about 100 times ensuring a solid flow of coolant with no bubbles, if there is air in there its magic air. We have also drained and refilled the system using a vacuum filling system at least 4 times, cracking the heat core lines between to ensure no air. And we used a section of clear hose so we could see the air was evacuated. |
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Joshwa
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Location: North Seattle WA
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| Posted: Thu Mar 15, 2018 11:13 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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On the return circuit, the only obstruction is the aux pump, which would cause the rear to not heat if obstructed.
| markcm2 wrote: |
The inlet side gets hot but the outlet side is much cooler, it’s as if there is backpressure on the outlet side.
If you hold both sides of the front heater core and squeeze one side in a pulsing motion you can feel the fluid freely moving through the core and pulsing on the other side as well. |
Going back to the post, if you are connected up as the diagram shows, you shouldn't have any backpressure to keep the coolant from flowing. When looking in the engine bay, aside from the diagram, doesn't the out put join up with the rear output near to exit of rear heater shutoff valve?
And if you've pinched off the rear input where it y's off from the front core input, I would think that would force the coolant through the front core, as it would have no where else to go.
_________________
93 Weekender TDI conversion (AHU)
93 MV TDI conversion (1Z)
Weekender rear cot
Late model cabin air filter on 93
Euro spec bumper install on 93
Last edited by Joshwa on Thu Mar 15, 2018 11:22 am; edited 1 time in total |
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markcm2
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Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 11:20 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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We haven't tried pinching off the rear yet. That's an idea to add to our troubleshooting.
We are finding there is no air flow to the floor when floor is selected which may indicate the heater box might not have been re-assembled correctly. We did pull off all the foam and cover the plates with foil tape but, something is not right here so we'll need to investigate that further as well. Maybe its a mixing issue but if there's no air flowing through the front heat core, why would it drop so much temperature across the core and why would heat increase with RPM. |
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markcm2
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Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 11:53 am Post subject: Re: Help diagnose no coolant flow through front heater core |
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| Floor air resolved, it was a loose control cable. |
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markcm2
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Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 12:07 pm Post subject: Re: Help diagnose no coolant flow through front heater core |
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| Jumped power to the auxiliary water pump and it appears to be non-functional (no sound or vibration). Will continue to investigate this along with replacing the pneumatic heat valve. |
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markcm2
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Posts: 505
Location: Bellingham, Washington
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| Posted: Thu Mar 15, 2018 7:07 pm Post subject: Re: Help diagnose no coolant flow through front heater core |
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Replaced the electric auxiliary water pump and we've got heat now. I'd say the heat is performing about 85% compared to no heat at idle and a trickle under load.
Cooling system temperature is a bit erratic as we still need to put in a new "heat control valve." |
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Joshwa
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pinetreeporsche
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| Posted: Sat Mar 17, 2018 1:42 pm Post subject: Re: Help diagnose no coolant flow through front heater core |
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| Different variation of a heat problem: Just got a Winnebago full-camper and have plenty of heat in the front. I'm trying to find out where any heat may come from to serve the rest of the van. There's a sloping, louvered plastic fitting, about 4 in by 5, just to the pass. side of the centerline of the van, right where the front floor level drops down to the main floor level. I thought because of the louvers it should be an air outlet, but nothing comes out. The small dial above the 3 big ones on the heater panel has numbers- is that for a fan in that unit? (Seems awful small to heat the whole rear- smaller than the r outlet in my Vanagon Westy.) IS there another location of heater-air outlet in the back? |
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Zeitgeist 13
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| Posted: Sat Mar 17, 2018 1:56 pm Post subject: Re: Help diagnose no coolant flow through front heater core |
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Not sure what year you have, but on mine there's a switch on the dash that enables the rear controls to function. The sloped louvered piece is the outlet and the inlet is in the slider threshold.
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Casey--
'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik? |
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