1/6/22, 2:58 PM

TOPIx - SSM75559 - AJ20-P4 engine – Coolant leak from Thermostat

Reference

SSM75559

Models

E-PACE / X540
F-PACE / X761
F-TYPE / X152
XE / X760
XF / X260

Title

AJ20-P4 engine – Coolant leak from Thermostat

Category

Driveline

Last modified

03-Dec-2021 00:00:00

Symptom

510000 Fluid Concerns

Content

Issue: JLR is investigating AJ20-P4 thermostats with complaints for coolant leaks (on any vehicle) that
are coming into service with evident leak or with low coolant MIL warning [sometimes associated with
P0128 DTC]
Causes: JLR investigation in progress
Action: If you see this issue present on a vehicle, and if you suspect the coolant leak is from
the thermostat
A. Gross leak from thermostat
1. Screenshot of the latest DTCs / warning light
2. Share video evidence of fresh leak
3. Check if the housing is sitting properly – refer image (A) attached. If there are signs of incorrect
assembly, replace the thermostat with a new
4. If no issue found in step (3), document evidence of location and reason for gross leak and replace the
part with a new one

B. Evident fresh leak [not gross] from thermostat.
1. Screenshot of the latest DTCs / warning light
2. Share video evidence of fresh leak
3. Clean the fresh leak thoroughly and also ensure the grooves do not hold any residual coolant
4. Test drive the car for about 30 minutes and check for leak again
5. If there is a leak, provide video evidence of the leak and proceed with replacing the part with a new
one.
6. If there is no leak, perform the standard cooling system pressure test and show evidence that leak is
observed in thermostat
7. If the pressure test does not confirm leak on the thermostat, do not change the thermostat. Check
rest of the coolant circuit for leak

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1/6/22, 2:58 PM

TOPIx - SSM75559 - AJ20-P4 engine – Coolant leak from Thermostat

C. No evident fresh leak but only dried up coolant deposit is seen on the body of the thermostat [Image B]
1. Screenshot of the latest DTCs / warning light
2. Confirm if there was any external coolant spill [either at dealer end or customer end]
3. Check the coolant pipes on top of / around the thermostats for any leak / damage [pipes which has
possibility of leaking coolant to the thermostat body]
4. Clean the thermostat surface and the suspect leak location thoroughly [without removing thermostat
from the engine]
5. Make sure the grooves do not contain any residual coolant.
6. Test drive the car for about 30 minutes and inspect the thermostat again for any fresh leak
7. If there is no leak, perform the standard cooling system pressure test and show evidence that leak is
observed in thermostat
8. If the pressure test does not confirm leak on the thermostat, do not change the thermostat. Check
rest of the coolant circuit for leak
NOTES:
If the car comes in for repeat failure, perform the same checks as above. But replace the part with a
new one and prepare the removed part for return to Engineer.
Thermostats as a whole is a serviceable part. So, do not manipulate the thermostats in anyway.
If P0128 DTC Is present, first perform actions as per TOPIX against the DTC prior to performing the
actions in SSM.

Please raise an EPQR and attach all the information identified plus the session file(s), photograph(s) and
video(s)
Thank you for your assistance with this matter.
anBhdHRlcnM7MjAyMi0wMS0wNlQxOTo1Nzo0Mi42NjhaOzEzNi4yMjYuNDguODg7

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