Does rear heater get as hot as front heater?

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dealmaker

dealmaker

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2006 LX w/143k babied So Cal miles, second owner since 2009. In the middle of doing a coolant system cleaning and in a few days I'll finish with repeated cleansing flushings with distilled, then new SLLC.

Using ThermoCure, it's in the system right now, driven 1-1.5 hrs daily the past few days, and burping in between, and the front heaters are back to cranking out tons of heat, which was missing before this process.

However, the rear heater vents (under front seats and center console base), while getting warm, don't crank out really hot air. Everything for the rear heat is on correctly.

Suggestions? Maybe still some air pockets or sediment? Or does the rear heater just not crank out the heat like the front?
 
Rear heat should feel the same (hot) as front. Make sure rear fan (under DS seat) working and blowing high. Typically air bubbles/pockets come out rear first, front second.

Did you see something to make you think a stop-leak added?

Typically we avoid D. Water or chemical flushing, on 04 up. Since they use pre mix SLL. As we never get it all out, which than dilutes new SLL. Blowing out system, with 15PSI to 30PSI shop air helps get ~90% of liquid out. Do not go higher than 15PSI, unless a downstream drain or hose open. I attach shop air to reserve line, while rad cap on.

You can disconnect heater tees. Blow air in PS lower (rear core hose) and catch out DS lower hose. Which is reverse flow of coolant. I use a plastic milk jug as catch, to inspect what comes out. Air should pass unobstructed. Same can be done for front core.
 
2001LC said:
Rear heat should feel the same (hot) as front. Make sure rear fan (under DS seat) working and blowing high. Typically air bubbles/pockets come out rear first, front second.

Did you see something to make you think a stop-leak added?

Typically we avoid D. Water or chemical flushing, on 04 up. Since they use pre mix SLL. As we never get it all out, which than dilutes new SLL. Blowing out system, with 15PSI to 30PSI shop air helps get ~90% of liquid out. Do not go higher than 15PSI, unless a downstream drain or hose open. I attach shop air to reserve line, while rad cap on.

You can disconnect heater tees. Blow air in PS lower (rear core hose) and catch out DS lower hose. Which is reverse flow of coolant. I use a plastic milk jug as catch, to inspect what comes out. Air should pass unobstructed. Same can be done for front core.
Click to expand...
Thank you for this, very helpful!

No sign of any leaks since I replacesd the radiator and t's 3 yrs ago. Also never had stop-leak or similar, and I've owned since 2009 and bought out original lease from a best friend of mine so I know its history from Day 1.

I was afraid of never getting all of the old fluids out, especially from the cores, so I bought a ton of D water to flush it with repeatedly, and also bought this HF Cooling System Test and Refill Kit... Cooling System Test and Refill Kit - https://www.harborfreight.com/cooling-system-test-and-refill-kit-64985.html Any opinion of this tool? I'm thinking I'll try your suggestion of blowing thru reservoir line first. I originally tried to get the hoses off the heater core tubes to backflush, but didn't want to risk damaging when I realized is would be a battle to get them off. If I can't get anywhere with your blown air method, nor the HF tool, then I'll bite the bullet and cut the hoses to backflush, and simply replace them again...I already have the cable plier tool so the clamps are simple to deal with.
 
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Blowing into reservoir hose. Is to aid blowing out block during a flush. It's not very effective with cores. Also you'll need to catch what you blow out of heater cores, to inspect. So heater tees need to come out.

So to blow-out heat cores. You 'll really want to remove heater tees. If you've not replace the tees, now's the time. I always replace the first short 90 degree hot side hose, when I replace tees. It's the one attached to pipe coming up from rear engine water by pass on driver side. Make sure you do not put sideways pressure on the pipe. It's only pressed into water-by-pass joint rear, and can come loose.

Do not remove hoses from pipe coming out fire walls. Those pipes bend/crush easy.

But before doing anything. Make sure air out of coolant system. By:
  1. Run engine at operating temp.
  2. Drive with heat on hot (start heater dialing up to hot, with fans on. You can turn off fans afterward, if you like) and hard brake a few times.
  3. Park with front-end higher than rear.
  4. Let cool over night (8 hours).
  5. Before sun comes up and heat air. Check coolant level under radiator cap. Top with coolant, right up to bottom of neck/cap. Fill reservoir to full line.
If any coolant was needed in radiator, to top. Repeat all 5 steps.

Notes:
OEM Thermostat must be in good working order. Its jiggle valve, must be at top. This is an air bleed valve.
OEM Cap must be in perfect working order.
Make sure no restriction in reservoir cap or hose. Hose must go straight down to bottom of reservoir.
 
additionally:

Make sure rear heat controls set to HOT.
Make sure rear fan on.
Make sure rear fan is blowing air through rear air/heat vent. I've seen the intake (under drivers seat) of blow fan clogged.
 
Trunk Monkey said:
You said everything for the rear heat is on correctly, but more than one person here hasn't realized there's separate controls for the rear above the second row. Simple thing to check too.
Click to expand...
Yup. everything's properly on...owned this one for 14 yrs now...I even know about the glovebox dampener and the hidden cupholders in the front center compartment lid :D

Rear heat's luke warm at best so far. Gotta be either blockager in the core, or just a super pita to burp, but like @2001 mentioned, usually it's the front one that's a pita.

Not sure if there's a rear thermistor in the little grill above the 2nd row. If so, wondering if my DVD-player removal could've disconnected anything there?? I guess I'll have to check that out if this mornings burping and filling efforts don't improve things. Still really trying to avoid pulling hoses and tee's as those were replaced 3 yrs ago aong with radiator, thermostat, inlet and outlet hoses, all parts OEM.
 
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Rear heater for the 3rd row on mine doesn’t work either.
It has nothing to do with removal of DVD.
In one of my video I said my 3rd row heater isn’t working and someone left this comment.
Please read this comment in this screenshot.
IMG_3973.webp
 
Kamran Khan said:
Rear heater for the 3rd row on mine doesn’t work either.
It has nothing to do with removal of DVD.
In one of my video I said my 3rd row heater isn’t working and someone left this comment.
Please read this comment in this screenshot.
View attachment 3322961
Click to expand...
Yes, the rear HVAC seems to consist of two separate operations/systems. Heat will only come out at the vents under the inside-rear corners beneath the two front row seats, and at the vents at the bottom of the rear part of the center console between the front row seats. For A/C at the rear, cold will only come out of the cealing vents. I think there are separate fans for the rear heat, and for the rear A/C?? The fan for the rear heat is under the drivers seat (move DS seat all the way forward and up). I did a couple of flushes today and am still seeing sediment come out at the engine block drains...again the first flow was a trickle, so I unscrewed the drain plug bolt all the way and the flow increased as it came out both the bolt hole and the drain tube. Then I reamed the bolt hole with a plastic ziptie and broke loose sediment and flow increased dramatically. I guess that will be my game plan on my remaining flushes. That, and following @2001s five steps above in post #4, and idling at 2000-2500 RMP and just watching the bubbles come up (using a burping funnel), and it's making a diference. Rear heater is already blowing warmer air. If it doesn't improve further, I'll try @2001's method of tee removal, starting with the hoses coming from/to the block, and leaving the other hoses attached to their respective heater core tubes.
 
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You know this 06LX w/143K well!
But make no mention of anything as to why coolant system, would be clogged, rad replaced or why ThermoCure used? Or did I miss something?

A clean 06 SoCa properly maintained coolant system. Would NOT have sediment clogging it. So what's the story here?

Have you been monitoring engine coolant temp (ECT). In 06, I see ECT of 184-187F with OAT under ~65F. With higher OAT on sunny day, say 90F; I get ECT of 194F to 197F. If your running cooler. It be a sign of issues with: Thermostat, Rad Cap or air in system or combination of! If running hotter, same 3 may possibly, but radiator fins very likely clogged.

I said rear heat blows as hot as front. May be an over-statement. It's fan doesn't seems as strong, it's air deliver tube and it's core are bit smaller than front. So rear may not "feel" as hot. But should be hot!

I don't recall if there is a second air sensor for rear HVAC. If so, I'd think in rear headliner area you mentioned. Front is 6" below IG key, near drives knee.

_____________________
I'll ramble on a bit more:

Heat tees & hose 3 years ago. I would not be concerned "in the least", with pull off today. Although I never like pulling any hoses needlessly, we must at times. Even if factory hoses never replaced, newer tees aren't going to break.
Blowing out cores from tee hoses (reverse flow), is useful and gets 98% of fluid and or solids from cores. I do it often when I suspect some plastic, rubber or FIPG got in a core. Which could possible restrict flow through core(s).

Note on stuff found in system (not rust or chemical). I've found FIPG & plastic 3 places. Behind thermostat, inlet side of engine oil cooler & heater cores.

Since you've used D water & ThermoCure. I'd also flush again the earlier of; 2 years or 30K miles (as if red Toy LL was used). It will take a few flushing before you'll have proper mix again w/Pink. When I say, "flushing" in 04-up. That is without using D. water or any chemical. Just drain block, blowout, fill w/SLL and burp system. In systems 98-03 with RED 100% (Toy LL) we can & do use D. Water to flush. Those RED systems, lend themselves to a D. water and or Chimerical flush. As it's not a premixed coolant like Pink (Toy SLLL). So we must add D. Water anyway!

I'll repeat. Very important thermostat (jiggle valve up), cap and res hose all in good working order.

Using 15PSI air through reservoir hose w/cap on. Works well to blowout block, block drain(s), oil cooler & rad. Not very effective on heater cores, but helps to get some (50%) liquid pushed into block. When blowing out heater cores from Tees. I will use higher air pressure (30 even 40 PSI), provided other end open (blowing into a catch can). As system will not be getting pressurize, since we have flow through.

I do not see block drains slow or even clogged, unless a reason:
  • Block drains never opened before. Which on 06 w/150K, it may be slow at worst.
  • Tap water used in system (even just to flush) or some off-the-shelf coolant not compatible with SLL added in. These may cause electrolysis, scaling, jelling and thus clogging.
  • System neglected, over the long term.
  • Stop leak or other chemicals added.
ThermoCure should not be needed, in your system. Unless neglected or something happen to system.

When I do chemical flushes. I use BG products for: scaling or if stop leak every used. I've not but may use CRC product, if I had to for rust. Which I'd likely use CRC EvapoRust (they bought the company).

A properly maintained system, will never need more than drain, blow, fill & burp.
 
2001LC said:
You know this 06LX w/143K well!
But make no mention of anything as to why coolant system, would be clogged, rad replaced or why ThermoCure used? Or did I miss something?

A clean 06 SoCa properly maintained coolant system. Would NOT have sediment clogging it. So what's the story here?

Have you been monitoring engine coolant temp (ECT). In 06, I see ECT of 184-187F with OAT under ~65F. With higher OAT on sunny day, say 90F; I get ECT of 194F to 197F. If your running cooler. It be a sign of issues with: Thermostat, Rad Cap or air in system or combination of! If running hotter, same 3 may possibly, but radiator fins very likely clogged.

I said rear heat blows as hot as front. May be an over-statement. It's fan doesn't seems as strong, it's air deliver tube and it's core are bit smaller than front. So rear may not "feel" as hot. But should be hot!

I don't recall if there is a second air sensor for rear HVAC. If so, I'd think in rear headliner area you mentioned. Front is 6" below IG key, near drives knee.

_____________________
I'll ramble on a bit more:

Heat tees & hose 3 years ago. I would not be concerned "in the least", with pull off today. Although I never like pulling any hoses needlessly, we must at times. Even if factory hoses never replaced, newer tees aren't going to break.
Blowing out cores from tee hoses (reverse flow), is useful and gets 98% of fluid and or solids from cores. I do it often when I suspect some plastic, rubber or FIPG got in a core. Which could possible restrict flow through core(s).

Note on stuff found in system (not rust or chemical). I've found FIPG & plastic 3 places. Behind thermostat, inlet side of engine oil cooler & heater cores.

Since you've used D water & ThermoCure. I'd also flush again the earlier of; 2 years or 30K miles (as if red Toy LL was used). It will take a few flushing before you'll have proper mix again w/Pink. When I say, "flushing" in 04-up. That is without using D. water or any chemical. Just drain block, blowout, fill w/SLL and burp system. In systems 98-03 with RED 100% (Toy LL) we can & do use D. Water to flush. Those RED systems, lend themselves to a D. water and or Chimerical flush. As it's not a premixed coolant like Pink (Toy SLLL). So we must add D. Water anyway!

I'll repeat. Very important thermostat (jiggle valve up), cap and res hose all in good working order.

Using 15PSI air through reservoir hose w/cap on. Works well to blowout block, block drain(s), oil cooler & rad. Not very effective on heater cores, but helps to get some (50%) liquid pushed into block. When blowing out heater cores from Tees. I will use higher air pressure (30 even 40 PSI), provided other end open (blowing into a catch can). As system will not be getting pressurize, since we have flow through.

I do not see block drains slow or even clogged, unless a reason:
  • Block drains never opened before. Which on 06 w/150K, it may be slow at worst.
  • Tap water used in system (even just to flush) or some off-the-shelf coolant not compatible with SLL added in. These may cause electrolysis, scaling, jelling and thus clogging.
  • System neglected, over the long term.
  • Stop leak or other chemicals added.
ThermoCure should not be needed, in your system. Unless neglected or something happen to system.

When I do chemical flushes. I use BG products for: scaling or if stop leak every used. I've not but may use CRC product, if I had to for rust. Which I'd likely use CRC EvapoRust (they bought the company).

A properly maintained system, will never need more than drain, blow, fill & burp.
Click to expand...
Thank you for this!

Never had any overheating issues, and AFAIK, the vehicle was always serviced by either local Lexus dealer, or local independent Toy/Lexus-certified master mechanic who says they only use OEM parts and fluids. Two coolant changes during that time...2009 @ 30k, and 2014 @ 86k miles...before radiator was changed in 12/2019.

The only thing I can think of is when I replaced radiator/cap/thermo/gasket, upper/lower hoses, tees (but not the hoses attached to the tees), all OEM, in 12/19, after radiator plastic had discolored and showed a small leak. We flushed the heater cores at that time with...don't ban me...tap water :frown:. And afterwards flushed the cores again w/distilled and sucked it out w/shop vac, and chased with SLLC again drawing from shop vac. Only thing I can think of is we didn't get all of the water out :mad:. In 2021 I drained radiator and reservior and refilled w/SLLC. It was after that I noticed the heater didn't seem to run as hot so I likely didn't burp properly. Read on a few forums that ThermoCure had resolved some problems w/heater core issues so I dropped my guard and decided to give it a go, and here we are.

Completed 2nd flush after the ThermoCure treatment today and still some sediment (non-magnetic), and heat output continues to get improve. I figure I have at least 2-3 more flushed with D water before I can consider SLLC. In a year I'll flush again following your guidelines above.

If I'm still getting sediment 3 flushes from now I'll probably pull the tees and try a more direct approach. I just realized today that when I replaced the tees in 2019, didn't replace those hoses :oops: . BTW my orig tees looked like they had lots of life left in them when I replaced them. The original hoses still look good now, but at least I'm less concerned about replacing them knowing they're 17 yrs old. Reservoir hose seems good...no blockage no splits.
 
Sounds like you'll have system working well soon. Good Job!

A little on your old Rad:
Discolored radiator plastic, at that age/miles w/2 coolant changes. Tells me air was in the system for a good amount of time, and likely was running hot. Air in the system, pockets in top of radiator after cool down. More so when parked level or front end higher than rear end. Then plastic drys out the in air. I see many, that Toyota/Lexus Dealership or Toy/Lex shops. That Do Not burp air completely. They'll bank on vacuum or special funnels get all air out or enough. I find we must check under the radiator cap in the 4.7L, after over night cool down.
 
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