How to replace a thermostat in a cooling system on 1996 through 2002 Toyota 4Runner?

First thing, before you replace the thermostat, check the coolant level, drivebelt tension, and temperature gauge. For replacement of the thermostat, detach the negative cable on your battery, drain the cooling system, and gently detach the thermostat housing from the vehicle. Reinstall the thermostat as well as the housing, tighten the fasteners, and refill the cooling system.

How to replace the thermostat on 2003 through 2009 Toyota 4Runner?

Before proceeding, check the coolant level and the drive belt tension, and then check the operation of the temperature gauge. If the engine takes a long time to warm up, the thermostat is probably stuck open. Replace the thermostat. If the engine runs hot, check the temperature of the left-side radiator hose (V6 models) or the right-side radiator hose (V8 models). If the hose isn't hot, the thermostat is probably stuck shut. Replace the thermostat. If the radiator hose is hot, then the coolant is circulating into the radiator and the thermostat is open. If the engine has overheated, it might have leaking cylinder head gaskets, scuffed pistons, or warped or cracked cylinder heads. To replace the thermostat, disconnect the cable from the negative terminal of the battery. Drain the cooling system. If you're working on a V6 model, remove the engine cover. Detach the thermostat housing from the engine. Be prepared for some coolant to spill as the gasket seal is broken. On V8 models, the radiator hose can be left attached to the housing, unless the housing itself is to be replaced. Remove the thermostat, noting the direction in which it was installed in the housing. Thoroughly clean the sealing surfaces. On V8 models, install a new gasket onto the thermostat. Make sure it fits evenly all the way around. On V6 models, install a new O-ring in the housing groove. On V8 models, install the thermostat and housing, positioning the jiggle pin, if equipped, at the highest point. Be sure the jiggle pin is not positioned more than 30 degrees right or left of the highest point. Tighten the housing fasteners to the torque and reinstall the remaining components in the reverse order of removal. Refill the cooling system, run the engine, and check for leaks and proper operation.

Genuine Toyota 4Runner Thermostat

Engine Coolant Thermostat

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11 Thermostats found

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Toyota 4Runner Thermostat
Part Number: 90916-03100
$24.03 MSRP: $33.58
You Save: $9.55 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 2003-2007 Toyota 4Runner | Limited, SR5 | 8 Cyl 4.7L | 2UZFE; 2UZFE; UZN210L-GKAGKA, UZN210L-GKAZKA, UZN215L-GKAGKA, UZN215L-GKAZKA
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Toyota 4Runner Thermostat
Part Number: 90916-03075
$27.48 MSRP: $38.41
You Save: $10.93 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1996-2002 Toyota 4Runner | LULI, SR5B, SR5V | 6 Cyl 3.4L | 5VZFE; 5VZFE; VZN180L-GKPGKA, VZN180L-GKPSKA, VZN180L-GKPZKA, VZN185L-GKMGKA, VZN185L-GKPGKA, VZN185L-GKPSKA, VZN185L-GKPZKA
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Toyota 4Runner Thermostat
Part Number: 90916-03093
$22.48 MSRP: $31.42
You Save: $8.94 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 2010-2012 Toyota 4Runner | 4 Cyl 2.7L | 2TRFE; 2TRFE; TRN280L-GKPGKA, TRN285L-GKPGKA
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Toyota 4Runner Thermostat
Part Number: 90916-03078
$21.87 MSRP: $30.58
You Save: $8.71 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 88-100
- Replaces: 90916-03036, 90916-03022, 90916-03055, 90916-03040, 90916-03029, 90916-03023
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1984-1995 Toyota 4Runner | DLX, SDT, SR5, SR5 Turbo, STD | 4 Cyl 2.4L | 22R, 22RE, 22REC, 22RTEC; 22R, 22RE, 22REC, 22RTEC; RN101L-TRLDEA, 22RTEC; RN50L-KRA, RN101L-TRLDEAB, RN101L-TRLDEK, RN101L-TRLSEA, RN101L-TRLSEA3, RN101L-TRMDEA, RN101L-TRMDEA3, RN101L-TRMDEAB, RN101L-TRMDEK, RN101L-TRMSEA, RN101L-TRMSEA3, RN101L-TRPDEA, RN101L-TRPDEAB, RN106L-TRLDEA, RN106L-TRLDEK, RN106L-TRMDEA, RN106L-TRMDEA3, RN106L-TRMDEK, RN106L-TRPDEA, RN106L-TRPDEA3, RN106L-TRPDEK, RN110L-CRLDEA, RN110L-CRLDEK, RN110L-CRLSEA, RN110L-CRLSEA3, RN110L-CRMDEA, RN110L-CRMDEA3, RN110L-CRMDEAB, RN110L-CRMDEK, RN110L-CRMSEA, RN110L-CRMSEA3, RN110L-CRPDEA, RN110L-CRPDEA3, RN110L-CRPSEA, RN110L-CRPSEA3, RN120L-GKPSEA, RN121L-RKMSEK, RN121L-RKPSEK, RN130L-GJLSEA, RN130L-GJMSEA, RN130L-GJPSEA, RN130L-GKLSEA, RN130L-GKMSEA, RN130L-GKPSEA, RN131L-RJLSEK, RN131L-RJMSEK, RN131L-RJPSEK, RN131L-RKLSEK, RN131L-RKMSEK, RN131L-RKPSEK, RN50L-KRA, RN50L-KRK, RN50L-LRA, RN50L-MRA, RN50L-MSEA, RN50L-MSEA3, RN50L-PRA, RN50L-SRA, RN50L-SREA, RN50L-TRA, RN55L-KDA3W, RN55L-KDEA3W, RN55L-KDEK3W, RN55L-KDK3W, RN55L-KRA3W, RN55L-KREA3W, RN55L-KRTEA3W, RN55L-LDA, RN55L-LDA3, RN55L-LRA, RN55L-MDA, RN55L-MDA3, RN55L-MDCA, RN55L-MDCA3, RN55L-MDCK, RN55L-MGCZA, RN55L-MGCZA3, RN55L-MRA, RN55L-MRHA, RN55L-MRHA3, RN55L-MRHEA, RN55L-MRHEK, RN55L-MRHK, RN55L-MRK, RN55L-MSCEA, RN55L-MSCEA3, RN55L-MSCEK, RN55L-MSCZA, RN55L-MSCZA3, RN55L-MSEA, RN55L-MSEA3, RN55L-MSEK, RN55L-PDA, RN55L-PDA3, RN55L-PDCA, RN55L-PDCA3, RN55L-PDCK, RN55L-PDEA3W, RN55L-PDEK3W, RN55L-PDK, RN55L-PGCZA, RN55L-PGCZA3, RN55L-PGCZK, RN55L-PRA, RN55L-PRK, RN55L-PSCEA, RN55L-PSCEA3, RN55L-PSCEK, RN55L-PSEA3, RN55L-SDA, RN55L-SDEA, RN55L-SDEA3, RN55L-SRA, RN55L-SREA, RN55L-SREA3W, RN55L-SREK, RN55L-SRHEA, RN55L-SRHEK, RN55L-SRK, RN55L-SRTEA3W, RN60L-MDK, RN60L-MRA, RN60L-MRA3, RN60L-MSA, RN60L-MSA3, RN60L-MSEA, RN60L-MSEA3, RN60LG-MDA, RN60LG-MDEA, RN60LG-MSA, RN60LG-MSEA, RN60LG-PDEA, RN60LV-MDA, RN60LV-MDEA, RN60LV-MSEK, RN60LV-MSK, RN60LV-PDEA, RN60LV-PSEK, RN61L-MBZA, RN61L-MBZA3, RN61L-MDK, RN61L-MRA, RN61L-MRA3, RN61L-MREA, RN61L-MREA3, RN61L-MREK, RN61L-MSEA, RN61L-MSEA3, RN61LG-MDEA, RN61LG-MSEA, RN61LG-PDEA, RN61LG-PGZA, RN61LG-PSEA, RN61LV-MDEA, RN61LV-MDEK, RN61LV-MSEA, RN61LV-MSEK, RN61LV-PDEA, RN61LV-PDEK, RN61LV-PGZK, RN61LV-PSEA, RN61LV-PSEK, RN65L-MDA, RN65L-MDA3, RN65L-MDCA, RN65L-MDCA3, RN65L-MDK, RN65L-MSA3, RN65L-MSCA, RN65L-MSCA3, RN65L-MSCEA, RN65L-MSCEA3, RN65L-MSCEK, RN65L-MSCK, RN65L-MSEA3, RN65L-MSEK, RN65L-MSK, RN65L-PDCEA, RN65L-PDCEA3, RN65L-PDEA, RN65L-PDEA3, RN65L-PDEK, RN65L-PSCEK, RN66L-MDA, RN66L-MDA3, RN66L-MDCA, RN66L-MDCA3, RN66L-MDCEA, RN66L-MDCEA3, RN66L-MDCEK, RN66L-MDEA, RN66L-MDEA3, RN66L-MDEK, RN66L-MDK, RN66L-MGCZA, RN66L-MGCZA3, RN66L-MGCZK, RN66L-MRA, RN66L-MSCEA, RN66L-MSCEA3, RN66L-MSCEK, RN66L-MSEA3, RN66L-MSEK, RN66L-PDCEA, RN66L-PDCEA3, RN66L-PDEA, RN66L-PDEA3, RN66L-PDEK, RN66L-PGCZA, RN66L-PGCZA3, RN66L-PGCZK, RN66L-PSCEA3, RN66L-PSCEK, RN70L-LDCA3, RN70L-LRCA, RN70L-LRCA3, RN70L-MDCA, RN70L-MDCA3, RN70L-MDCK, RN70L-MRCA, RN70L-MRCA3, RN70L-MRCK, RN70L-SDCA, RN70L-SDCA3, RN70L-SDCEA3, RN70L-SDCK, RN70L-SRCA, RN70L-SRCEA, RN70L-SRCEA3, RN70L-SRCEK, RN70L-SRCK, RN75L-KRTEA3W, RN75L-PDTEA3W, RN75L-SDTEA3W, RN75L-SDTEK3W, RN80L-TRKREA, RN80L-TRKRSA, RN80L-TRKRSA3, RN80L-TRLDSA, RN80L-TRLDSA3, RN80L-TRMDEA, RN80L-TRMDEA3, RN80L-TRMDEAB, RN80L-TRMREA, RN80L-TRMREAB, RN80L-TRMREK, RN80L-TRMRSK, RN80L-TRSDEA, RN80L-TRSDEA3, RN80L-TRSDEAB, RN80L-TRTRSA, RN80L-TRTRSA3, RN85L-TRLDSA, RN85L-TRLDSA3, RN85L-TRMDEA, RN85L-TRMDEA3, RN85L-TRMDEK, RN85L-TRMDSK, RN85L-TRMSEA, RN85L-TRMSEA3, RN85L-TRSDEA, RN85L-TRSDEA3, RN85L-TRSDEK, RN85L-TRSSEA, RN85L-TRSSEA3, RN90L-CRLDSA, RN90L-CRLDSA3, RN90L-CRMDEA, RN90L-CRMDEA3, RN90L-CRMDEAB, RN90L-CRMDEK, RN90L-CRMDSK, RN90L-CRMSEA, RN90L-CRMSEA3, RN90L-CRSDEA, RN90L-CRSDEA3, RN90L-CRSDEK, RN90L-CRSSEA, RN90L-CRSSEA3
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Toyota 4Runner Thermostat
Part Number: 90916-03120
$27.38 MSRP: $38.27
You Save: $10.89 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Replaces: 90916-03088, 90916-03101
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1996-2001 Toyota 4Runner | SR5B | 4 Cyl 2.7L | 3RZFE; 3RZFE; RZN180L-GKMSKA, RZN180L-GKPSKA, RZN185L-GKMSKA, RZN185L-GKPSKA
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Toyota 4Runner Thermostat
Part Number: 90916-03079
$27.72 MSRP: $38.74
You Save: $11.02 (29%)
Ships in 1-3 Business Days
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1987-1995 Toyota 4Runner | DLX, SR5, STD | 6 Cyl 3.0L | 3VZE; 3VZE; VZN100L-TRMDEA, VZN100L-TRMDEA3, VZN100L-TRMDEAB, VZN100L-TRMDEK, VZN100L-TRMGEA, VZN100L-TRMGEA3, VZN105L-TRMDEA, VZN105L-TRMDEA3, VZN105L-TRMDEK, VZN105L-TRPDEA, VZN105L-TRPDEA3, VZN110L-CRMDEA, VZN110L-CRMDEA3, VZN110L-CRMDEAB, VZN110L-CRMDEK, VZN110L-CRMGEA, VZN110L-CRMGEA3, VZN110L-CRMGEK, VZN110L-CRPDEA, VZN110L-CRPDEA3, VZN110L-CRPDEAB, VZN110L-CRPDEK, VZN110L-CRPGEA, VZN110L-CRPGEA3, VZN120L-GKPGEA, VZN130L-GJMGEA, VZN130L-GJPGEA, VZN130L-GKMGEA, VZN130L-GKPGEA, VZN131L-RJMGEK, VZN131L-RJPGEK, VZN131L-RKMGEK, VZN131L-RKPGEK, VZN61LG-MSEA, VZN61LG-PSEA, VZN61L-MBEA, VZN61L-MBEA3, VZN61L-MSEA, VZN61L-MSEA3, VZN61LV-MDEA, VZN61LV-MSEA, VZN61LV-MSEK, VZN61LV-PDEA, VZN61LV-PSEA, VZN61LV-PSEK, VZN66L-MDCEA3, VZN66L-MDCEK, VZN66L-MDEA3, VZN66L-MDEK, VZN66L-MSCEA, VZN66L-MSCEA3, VZN66L-MSCEK, VZN66L-PDCEA3, VZN66L-PDEA3, VZN66L-PDEK, VZN66L-PSCEA3, VZN66L-PSCEK, VZN85L-THMDEA, VZN85L-THMDEA3, VZN85L-THSDEA, VZN85L-THSDEA3, VZN85L-TRMDEA, VZN85L-TRMDEA3, VZN85L-TRMDEK, VZN85L-TRMREA6, VZN85L-TRSDEA, VZN85L-TRSDEA3, VZN85L-TRSDEK, VZN85L-TRSREA6, VZN85L-TWMREA6, VZN85L-TWSREA6, VZN90L-CRMDEA, VZN90L-CRMDEA3, VZN90L-CRMDEK, VZN90L-CRMGEA, VZN90L-CRMGEA3, VZN90L-CRMGEK, VZN90L-CRPGEA, VZN90L-CRPGEA3, VZN90L-CRSDEA, VZN90L-CRSDEA3, VZN90L-CRSDEK, VZN95L-TWMREA6, VZN95L-TWSREA6, VZN95L-TWSREK6
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Toyota 4Runner Thermostat
Part Number: 90916-03138
$41.28 MSRP: $57.71
You Save: $16.43 (29%)
Ships in 1 Business Day
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Product Specifications
- Manufacturer Note: *WAX 82-95
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 2006-2009 Toyota 4Runner | Limited, SR5 | 8 Cyl 4.7L | 2UZFE; 2UZFE; UZN210L-GKAGKA, UZN210L-GKAZKA, UZN215L-GKAGKA, UZN215L-GKAZKA
View related parts
Toyota 4Runner Thermostat
Part Number: 90916-03101
$27.38 MSRP: $38.27
You Save: $10.89 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Manufacturer Note: *WAX 82-95
- Replaced by: 90916-03120
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1996-1998 Toyota 4Runner | SR5B | 4 Cyl 2.7L | 3RZFE; 3RZFE; RZN180L-GKMSKA, RZN180L-GKPSKA, RZN185L-GKMSKA, RZN185L-GKPSKA
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Toyota 4Runner Thermostat
Part Number: 90916-03055
$21.87 MSRP: $30.58
You Save: $8.71 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Replaced by: 90916-03078
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1984-1988 Toyota 4Runner | DLX, SDT, SR5, SR5 Turbo, STD | 4 Cyl 2.4L | 22R, 22REC, 22RTEC; 22R, 22REC, 22RTEC; RN50L-KRA, RN50L-KRK, RN50L-MRA, RN50L-MSEA, RN50L-MSEA3, RN50L-PRA, RN50L-SRA, RN55L-KDA3W, RN55L-KDEA3W, RN55L-KDEK3W, RN55L-KDK3W, RN55L-KRA3W, RN55L-KREA3W, RN55L-KRTEA3W, RN55L-MDA, RN55L-MDA3, RN55L-MDCA, RN55L-MDCA3, RN55L-MDCK, RN55L-MGCZA, RN55L-MGCZA3, RN55L-MRA, RN55L-MRHA, RN55L-MRHA3, RN55L-MRHEA, RN55L-MRHEK, RN55L-MRHK, RN55L-MRK, RN55L-MSCEA, RN55L-MSCEA3, RN55L-MSCEK, RN55L-MSEA, RN55L-MSEA3, RN55L-MSEK, RN55L-PDA, RN55L-PDA3, RN55L-PDCA, RN55L-PDCA3, RN55L-PDCK, RN55L-PDEA3W, RN55L-PDEK3W, RN55L-PDK, RN55L-PGCZA, RN55L-PGCZA3, RN55L-PGCZK, RN55L-PRA, RN55L-PRK, RN55L-PSCEA, RN55L-PSCEA3, RN55L-PSCEK, RN55L-PSEA3, RN55L-SDA, RN55L-SRA, RN55L-SREA3W, RN55L-SRHEA, RN55L-SRHEK, RN55L-SRK, RN55L-SRTEA3W, RN60LG-MDA, RN60LG-MDEA, RN60LG-MSA, RN60LG-MSEA, RN60LG-PDEA, RN60L-MDK, RN60L-MRA, RN60L-MRA3, RN60L-MSA, RN60L-MSA3, RN60L-MSEA, RN60L-MSEA3, RN60LV-MDA, RN60LV-MDEA, RN60LV-MSEK, RN60LV-MSK, RN60LV-PDEA, RN60LV-PSEK, RN61LG-MDEA, RN61LG-MSEA, RN61LG-PDEA, RN61LG-PGZA, RN61L-MBZA, RN61L-MBZA3, RN61L-MDK, RN61L-MRA, RN61L-MRA3, RN61L-MSEA, RN61L-MSEA3, RN61LV-MDEA, RN61LV-MSEA, RN61LV-MSEK, RN61LV-PDEA, RN61LV-PGZK, RN61LV-PSEA, RN61LV-PSEK, RN65L-MDA, RN65L-MDA3, RN65L-MDCA, RN65L-MDCA3, RN65L-MDK, RN65L-MSA3, RN65L-MSCA, RN65L-MSCA3, RN65L-MSCEA, RN65L-MSCEA3, RN65L-MSCEK, RN65L-MSCK, RN65L-MSEA3, RN65L-MSEK, RN65L-MSK, RN65L-PDCEA, RN65L-PDCEA3, RN65L-PDEA, RN65L-PDEA3, RN65L-PDEK, RN65L-PSCEK, RN66L-MDA, RN66L-MDA3, RN66L-MDCA, RN66L-MDCA3, RN66L-MDK, RN66L-MGCZA, RN66L-MGCZA3, RN66L-MGCZK, RN66L-MRA, RN66L-MSCEA, RN66L-MSCEA3, RN66L-MSCEK, RN66L-MSEA3, RN66L-MSEK, RN66L-PDCEA, RN66L-PDCEA3, RN66L-PDEA, RN66L-PDEA3, RN66L-PDEK, RN66L-PGCZA, RN66L-PGCZA3, RN66L-PGCZK, RN66L-PSCEA3, RN66L-PSCEK, RN70L-MDCA, RN70L-MDCA3, RN70L-MDCK, RN70L-MRCA, RN70L-MRCK, RN70L-SDCA, RN70L-SDCA3, RN70L-SDCK, RN70L-SRCA, RN70L-SRCK, RN75L-KRTEA3W, RN75L-SDTEA3W, RN75L-SDTEK3W
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Toyota 4Runner Thermostat
Part Number: 90916-03062
$21.96 MSRP: $30.69
You Save: $8.73 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Replaced by: 90916-03099
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1984-1986 Toyota 4Runner | DLX, STD | 4 Cyl 2.4L | 2L, 2LT; 2L, 2LT; LN51L-KRA, LN51L-KRA3, LN56L-MDA3, LN56L-MDCA, LN56L-MDCA3, LN56L-MDCK, LN56L-MDCXA3, LN56L-MDK, LN56L-MDXA3, LN56L-MRK, LN65L-MDA, LN65L-MDA3, LN65L-MDCA3, LN65L-MDCK, LN65L-MDXA, LN65L-MDXA3, LN65L-MDXK, LN66L-MDCXK
View related parts
Toyota 4Runner Thermostat
Part Number: 90916-03054
$21.87 MSRP: $30.58
You Save: $8.71 (29%)
Ships in 1 Business Day
ADD TO CART
Product Specifications
- Manufacturer Note: *WAX 82-95
- Replaced by: 90916-03083
- Warranty: This genuine part is guaranteed by Toyota's factory warranty.
Fits the following Vehicles:
- 1985-1986 Toyota 4Runner | SR5 Turbo | 4 Cyl 2.4L | 22RTEC; 22RTEC; RN55L-MGCZA, RN55L-MGCZA3, RN55L-PGCZA, RN55L-PGCZA3, RN55L-PGCZK

Toyota 4Runner Thermostat

Toyota 4Runner Thermostat is an essential part of the car that is found in between the aluminum housing of the radiator and the vehicle engine. One of its main uses is to control the coolant flow to the engine to maintain its temperature, when the desired temperature is met, it closes. This mechanism ensures that the engines are on and warmed up much faster, less wear, enhanced efficiency, and minimal emission. Some 4Runner may face problems such overheating though at times it may take some time after replacing the thermostat, the water pump, and radiator cap to stop. The supply of fresh coolant must be done regularly to avoid formation of some minerals on the radiators. If the car radiator is cold, while the engine is hot, then this is ideal time to work on the thermostat replacement task.

If you are in demand for superior quality and affordable OEM Toyota 4Runner Thermostat, then shop with us! We own a wide range of the reduced-priced genuine Toyota 4Runner Thermostat. You can purchase in confidence as all parts come with a manufacturer's warranty. Any issues with our products? No need to worry as we have a hassle-free return policy to guide you every step of the way.

Toyota 4Runner Thermostat Parts Questions & Experts Answers

Thermostat
90916-03120
Q: How to replace a thermostat in a cooling system on 1996 through 2002 Toyota 4Runner?
A: First thing, before you replace the thermostat, check the coolant level, drivebelt tension, and temperature gauge. For replacement of the thermostat, detach the negative cable on your battery, drain the cooling system, and gently detach the thermostat housing from the vehicle. Reinstall the thermostat as well as the housing, tighten the fasteners, and refill the cooling system.
Thermostat
90916-03100
Q: How to replace the thermostat on 2003 through 2009 Toyota 4Runner?
A: Before proceeding, check the coolant level and the drive belt tension, and then check the operation of the temperature gauge. If the engine takes a long time to warm up, the thermostat is probably stuck open. Replace the thermostat. If the engine runs hot, check the temperature of the left-side radiator hose (V6 models) or the right-side radiator hose (V8 models). If the hose isn't hot, the thermostat is probably stuck shut. Replace the thermostat. If the radiator hose is hot, then the coolant is circulating into the radiator and the thermostat is open. If the engine has overheated, it might have leaking cylinder head gaskets, scuffed pistons, or warped or cracked cylinder heads. To replace the thermostat, disconnect the cable from the negative terminal of the battery. Drain the cooling system. If you're working on a V6 model, remove the engine cover. Detach the thermostat housing from the engine. Be prepared for some coolant to spill as the gasket seal is broken. On V8 models, the radiator hose can be left attached to the housing, unless the housing itself is to be replaced. Remove the thermostat, noting the direction in which it was installed in the housing. Thoroughly clean the sealing surfaces. On V8 models, install a new gasket onto the thermostat. Make sure it fits evenly all the way around. On V6 models, install a new O-ring in the housing groove. On V8 models, install the thermostat and housing, positioning the jiggle pin, if equipped, at the highest point. Be sure the jiggle pin is not positioned more than 30 degrees right or left of the highest point. Tighten the housing fasteners to the torque and reinstall the remaining components in the reverse order of removal. Refill the cooling system, run the engine, and check for leaks and proper operation.