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2010 Dodge Grand Caravan SXT 4.0L
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Guys - I may have found the solution. I've tried everything you all tried above except the water pump on my 2010 GC with 4.0L. Try bypassing the oil cooler (may be specific to 4.0L) and see if you get heat or at least hot return lines from the heater cores.

My initial symptoms in January

  • No rear heat
  • Partial front heat

My repairs in January / February
  • New front core without draining coolant ... no change in heat output
  • Drain coolant, new rear core, flush rear lines, new front hoses with aluminum y-fittings, prefill rear core and lines, new thermostat, refill radiator with new coolant, bleed system
  • Front heat is hot, rear lines are cold at idle but rear heat works at 2000 rpm and above.

Fast forward to September
  • Take van to repair shop for water pump and timing kit swap and mention all of the above on why I want the water pump.
  • Repair shop finds a small leak at the plastic thermostat housing and says cooling system won't hold pressure.
  • They convince me to go with a new thermostat housing and they will flush the cooling / heater system with water, air, and a cleaner before the timing and water pump job.
  • They find the "new" heater cores are plugged again, the lines going to the rear were partially plugged, the radiator had a lot of build up. All of these they are flushing separately.
  • They also find the oil cooler is completely blocked and they can't clear it. They bypassed this and coolant can freely flow to the cores now.
 

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2013 Dodge Grand Caravan
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5,576 Posts
That's a lot of clogged parts. Must have been some nasty coolant in it. What's the history on the coolant? How often (if ever) was it changed? What coolant type was used?
 

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2010 Dodge Grand Caravan SXT 4.0L
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That's a lot of clogged parts. Must have been some nasty coolant in it. What's the history on the coolant? How often (if ever) was it changed? What coolant type was used?
  • Purchased in 2014 with 60k miles (no maintenance history).
  • 2016 at 73k miles: Chrysler dealership performed a cooling system flush (no details on coolant type)
  • 2019 at 107k miles: added a gallon of 50/50 Peak coolant when the plastic y-fitting heater hoses cracked (no details on coolant type but it was probably one of those compatible with all types)
    • The only thing I can think of is that I replaced the plastic y-fittings with brass t-fittings on the heater hoses and the brass reacted with the coolant.
  • 2022 February at 133k miles: Zerex G-06 coolant which matched the spec in the owners manual, no radiator or chemical flush, just drained radiator and performed all of the work listed in the previous post.
 

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2013 Dodge Grand Caravan
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Mixing metals does tend to corrode things over time, but I'd expect that to eat away at passages, not clog them. Though I guess the material eaten away in other spots could collect in the thin heater core passages.

Given the history listed, I doubt it was old coolant coagulating. That first 6 year span between new and the first coolant flush could have had gelled coolant, but that would have been flushed out. Unless the Peak coolant was green or orange, it should have been compatible and not cause issues. Green would gel almost immediately, orange turns to mud in about 3 years.

Unless there was a leak sealant used, too high of a water concentration, or impurities in the water causing scaling; I'd suspect the mixed metals. Change it if you can, but if you can't find anything in aluminium or steel, just do coolant flushes every 3 years.
 
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2010 Dodge Grand Caravan SXT 4.0L
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I have the van back but after driving it home, I felt the rear heat and it isn't even warm. This is after they flushed everything, installed the new oil cooler, installed a new water pump, and new timing kit. The front heat is hot though. Time to take it back to the shop and have them find the blockage in the rear lines.

I did inspect the water pump. It has a plastic impeller, looks new and wasn't cracked or slipping on the shaft.

What is the deal with this engine / HVAC combo?
 

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2013 Dodge Grand Caravan
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I have the van back but after driving it home, I felt the rear heat and it isn't even warm. This is after they flushed everything, installed the new oil cooler, installed a new water pump, and new timing kit. The front heat is hot though. Time to take it back to the shop and have them find the blockage in the rear lines.

I did inspect the water pump. It has a plastic impeller, looks new and wasn't cracked or slipping on the shaft.

What is the deal with this engine / HVAC combo?
Double check your coolant level. I believe there is a flow restrictor going to the rear heater core. It's pretty common for those to clog. Hopefully it's something simple like that.

Where is the mixer door(s) on these cars? The one(s) that determines how much air passes through the heat cores?
What controls these?
5th gens all use blend doors. Earlier gens used heater valves. I'm not certain, but I think 3rd gen were the last to have them.
 

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2010 Dodge Grand Caravan SXT 4.0L
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Double check your coolant level. I believe there is a flow restrictor going to the rear heater core. It's pretty common for those to clog. Hopefully it's something simple like that.
Do you know where this flow restrictor is? The shop mentioned there are two "thermostats" on my 2010. They replaced the thermostat and housing on the engine but said this "2nd" one was ok. Maybe it is called something else besides a thermostat. I've never seen anything like this in repair manuals or parts lists.
 

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2013 Dodge Grand Caravan
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It's in one of the hoses.


 

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2010 Dodge Grand Caravan SXT 4.0L
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It's in one of the hoses.

Are you sure the 5th gen has a flow restrictor?
 

· Registered
2010 Dodge Grand Caravan SXT 4.0L
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10 Posts
I have the van back but after driving it home, I felt the rear heat and it isn't even warm. This is after they flushed everything, installed the new oil cooler, installed a new water pump, and new timing kit. The front heat is hot though. Time to take it back to the shop and have them find the blockage in the rear lines.

I did inspect the water pump. It has a plastic impeller, looks new and wasn't cracked or slipping on the shaft.

What is the deal with this engine / HVAC combo?
The shop has flushed more debris out of the system. The oil cooler was plugged again. I'm thinking an inline filter on the supply heater hose may help. Maybe even a filter on the top radiator hose. Anyone have experience with these or with debris / scale in these engine blocks?
 

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2013 Dodge Grand Caravan
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Someone probably used straight water in the system and it rusted a lot of stuff out. They don't rust out like that normally. You can try putting CLR in the system and letting it warm up a few times with that in there to break up some of the rust and then flush it once it cools down. At this point it would probably be best to change out the radiator and heater cores after everything appears to be flushed out. They may have pockets of sediment stuck in the tanks that may wiggle loose later.
 

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Friends, I'm desperate, I can't figure this out.

I have a 2010 T&C Limited with 4.0L and 3-zone ATC.

The car has little to no heat.

What I have done so far:
1) Topped off coolant, it's full
2) Replaced thermostat, original was fine.
3) Replaced cabin air filter (was very dirty). No difference.
4) Pulled apart dash and checked all blend door servos; all working.
5) Held the AUTO/SYNC button on the ATC to calibrate doors, no errors I can hear all front and rear servos cycle.
6) Pulled lines to heater core and reverse flushed them, some minor junk came out (coolant does have rusty color). Core runs freely. Inlet gets very hot, outlet still stays cold.

None of this has worked, still have no heat.

At idle, van blows cold air.
Revving the engine produces some heat, barely.
Driver's side in center console upper vents is warmish, passenger side is cold, never gets warm even on engine rev.

I have noticed that the A/C compressor clutch cycles on and off while idling - that's odd since it's 20 degrees outside here.

Bottom line, I'm out of ideas, and it's very cold here in the Northeast.

Any ideas? There is so little information on troubleshooting 4.0L vans. I've been all over many forums and YouTube with no luck.

Thank you!
I had the same problem...after blowing lines, h cores, changing water pump, tstat, radiator and front heater core, I found the oil cooler clogged with stop leak liquid aluminium. Pics and unclogging here: Cooling Sys Pickle
 

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I had no heat out of the rear vents in my 2010 Town & Country 4.0 minivan. I tried almost everything replaced the water pump, replaced the rear heater core, flushed the system, and installed a new thermostat.  Still rear heat was barely lukewarm if that. Knowing that water takes the path of least resistance, I put a restrictor valve after the Y connector on the pipe heading to the front heater core. This seems to have balanced out the system better, and is now sending hot fluid to the rear at the same flow to the front.


Motor vehicle Automotive tire Gesture Automotive design Automotive fuel system


Four Seasons Heater Control Valve 84707

https://a.co/d/3ZKS4GR

https://www.napaonline.com/en/p/BK_6601413
 

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538 RWHP, LS motor, RX7 body
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That's a fix, but what is causing that resistance differential in the circuit? The problem is still there.
You will know this weekend :) if enough total flow is going through both limbs for adequate heating.
 

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2010 Dodge Grand Caravan SXT 4.0L
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Having the same problem again. I think I'll bypass the (new) oil cooler and see if the flow increases to the heater cores. Wishing I installed inline filter(s) on the heater supply line and maybe the radiator hose. I really don't want to replace the radiator. After working on this and reading all of your posts above, I know flushing the cores are easy. I just don't want to spend anymore time and money on this problem.
 
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