Moss Motors, Ltd. Cobalt 910-850 User manual

Part # 910-850 910-855 -1- Modified 03/18
Coolant Reroute Kit
Installation Instructions
For 1994-1997 Miata 1.8L
PART # 910-850 and 910-855
Tools required:
• Timing Light
• Jack, jack stands, wheel chocks
• Phillips Head and Flathead Screwdrivers
• ¼" Ratchet
• " Ratchet
• 10mm Socket
• 12mm Socket
• 19mm Deep Socket
• " Deep Socket
• " Socket
• 5mm Allen Wrench
• 10mm Wrench
• 12mm Wrench
• 22mm or " Wrench
• Thread Sealant
• Razor blade or similar gasket scraper
• Radiator Hose Cutter
• Telescoping mirror (recommended)
• Spill-Free Funnel such as Lisle 24680 (recommended)
• Torque Wrench ¼" (recommended)
• Cooling System pressure tester (recommended)
Kit number 910-855 does not include an EGR
tube, EGR block off plate or block off nut. 910-855
is intended for an individual who has already done
away with the EGR system.
If your car presently has a working EGR system,
we recommend returning this kit and purchasing
Coolant Reroute Kit part# 910-850 which includes
a compatible EGR tube.
Removing the EGR tube and blocking off the ports
will turn the “Check Engine Light” on.
Notes: The stock coolant routing on the Mazda 1.8L
engine leaves much to be desired. Since the 1.8L
was originally developed for light-duty transverse-
mounted front wheel drive applications, little thought
was given to the rear-wheel drive Miata. Coolant
flows from the water pump at the front, through
passages in the engine to the rear of the cylinder
head. Some coolant can exit at the rear of the engine
but only through the small heater hose leading to the
heater core, a major flow restriction. The majority of
the coolant has to reverse direction and travel back
through the block again to exit at the thermostat at
the front of the engine; transferring unwanted heat
back into the block on the way. As a result of this
inefficient design, the rear cylinders run hotter than
the front. This can lead to a hotter running engine and
premature failures of the rear cylinders. The design is
especially problematic when a Miata is driven hard on
the track or modified for increased power output.
This kit will relocate the thermostat from the front of
the engine to the rear, thereby allowing coolant to
flow more efficiently one direction through the block.
The full-size radiator hose outlet at the rear of the
engine ensures maximum coolant flow is directed out
of the engine to the radiator. This helps to keep all
cylinders at a more uniform lower temperature.

Part # 910-850 910-855 -2- Modified 03/18
Installation Instructions
Warning:
• Let the engine cool for at least 6 hours before
opening the cooling system to avoid burn injury.
• Always use jack stands to support the weight
of the vehicle. Never rely on jack alone.
• Make sure to dispose of old coolant properly at
a recycling facility.
Removal:
1) Chock the rear wheels, jack up the front of the vehicle
and safely support on jack stands. Ensure engine is
cold. Drain the cooling system then reinstall the drain
plug. (You may need to remove the factory plastic
splash guard (if equipped) to access the radiator drain
plug.)
2) Remove the clamp retaining the hose to the Idle
Air Control valve. Remove the IAC hose and PCV
breather hose at the air tube. Loosen the screws
retaining the air intake tube to the throttle body and
air filter box. Remove the air intake tube. Figure 2.
Figure 2
3) Remove the two 10mm bolts retaining the metal
vacuum line for the power brake booster and throttle
cable. Remove the vacuum hose at the intake, and lift
the vacuum line up and out of the way. Figure 3.
Figure 3
4) Remove the one-wire connector for the coolant
temperature sensor (temp gauge) located on the
driver’s side back of the cylinder head, underneath
the camshaft position sensor. Figure 4.1. Remove
the connectors for the camshaft position sensor and
oxygen sensor. Position the wiring harness out of the
way. Figure 4.2.
Figure 4.2
Figure 4.1
5) Remove the three 12mm bolts retaining the coil
bracket to the back of the valve cover. You can
leave the spark plug wires and electrical connectors
connected to ease reassembly if desired. Carefully
lift the coil bracket up and place on top of the
valve cover, being careful not to damage the coil
connectors. Note: If you choose to remove the
electrical connectors at the coil be sure to mark
them, as they can be easily reversed and installed
in the wrong coil causing a no start. Figure 5.1.
Remove the green electrical connector for the two-
wire ECM coolant temperature sensor. Figure 5.2.

Part # 910-850 910-855 -3- Modified 03/18
Installation Instructions
Figure 5.2
Figure 5.1
6) Mark the position of the camshaft position sensor,
Figure 6.1. Then remove special retaining bolt with a
12 mm wrench, Figure 6.2. Only the bolt needs to be
removed, the sensor can stay in place.
Caution: Due to the retaining bolt being
removed, ignition timing MUST be checked
when installation is completed. Driving with
incorrect ignition timing may result in severe
engine damage!
Figure 6.1
Figure 6.2
7) Remove the temp sensor using a 19mm deep socket.
8) Remove the electrical connector for the Mass Air
Flow Sensor. Loosen the air intake duct and remove
the two 12mm bolts retaining the factor air filter box,
Figure 8.1. Remove the exhaust manifold heat shield
to gain access to the EGR tube, Figure 8.2.
Figure 8.1
Figure 8.2

Part # 910-850 910-855 -4- Modified 03/18
Installation Instructions
9) Loosen the EGR tube nut using a 7/8" or 22mm
wrench. Figure 9.
Figure 9
10) Loosen the two 10mm nuts at the back of the intake
manifold. Remove the stock EGR tube by rotating
upwards to clear the intake, then counter-clockwise,
Figure 10.1 and Figure 10.2.
Figure 10.1
Figure 10.2
11) Remove the heater hose clamp and heater hose from
the water neck at the rear of the cylinder head by the
firewall. Inspect the heater hose. Replace the heater
hose and clamp if they are old or in poor condition to
ensure against leaks. Figure 11.
Figure 11
12) Remove the 12mm nut and bolt retaining the heater
hose water neck at the rear of the cylinder head.
Remove the heater hose water neck and set aside.
Remove the stud from the rear of the cylinder head
(Use double nut method. The other nut can be
sourced from the front thermostat housing see step
12). Thoroughly remove all old gasket material with
a razor blade and clean the mating surface. Take
your time and clean thoroughly. It is helpful to use a
telescoping mirror to clearly see the mating surface.
Be sure that all old gasket material is removed.
Figure 12.
Figure 12

Part # 910-850 910-855 -5- Modified 03/18
Installation Instructions
13) Remove and discard the upper radiator hose.
Figure 13.
Figure 13
14) Remove the 12mm nut and bolt retaining the
thermostat housing at the front of the engine.
Remove the housing and set the thermostat aside,
Figure 14. Inspect the thermostat, you may wish
to replace the thermostat at this time if there is any
doubt that it is functioning properly. The thermostat
will be more difficult to access when this modification
is completed. Remove the stud from the housing
and set aside. Thoroughly clean the gasket sealing
surface.
Figure 14
Installation:
15) Apply a new thermostat gasket to the provided block
off plate and install in the former thermostat housing
location using the provided M8 bolts.
Torque to 16 ft.-lbs. Figure 15.
Figure 15
16) Install the provided heater hose barb in the reroute
spacer. The extra hole in the spacer is provided for
an aftermarket coolant temperature sensor. Use
the provided " NPT brass plug if you will not be
installing another sensor. The heater hose barb and
brass plug are pipe thread which means they seal on
the threads and do not bottom out. Excessive torque
may crack the reroute spacer or cause damage to the
parts being threaded in. Transfer the two-wire coolant
temperature sensor with washer from the old heater
hose water neck to the new radiator hose water neck.
Thread the sensor into the new spacer a few threads
but do not tighten down at this time. You will use the
loose sensor to bleed out air while filling the cooling
system. Figure 16.
Figure 16

Part # 910-850 910-855 -6- Modified 03/18
Installation Instructions
17) Install the thermostat in the recessed groove in the
spacer as shown with the air bleed hole at the top
as shown. The bleed hole should be clocked so that
it is closest to the factory coolant temp sensor. Peel
off the backing and stick a new thermostat gasket on
both sides of the reroute spacer. The gasket should
overlap over the thermostat slightly and help hold it
in place. The bleed hole in the thermostat should be
clocked so that it is closest to the factory coolant
sensor. Place the new radiator hose outlet neck on
the spacer oriented with the outlet neck opposite the
heater hose barb as shown. Figure 17.
Figure 17
18) Insert the 75mm and 50mm M8 bolts and keep the
assembly sandwiched together by hand ensuring
that the thermostat does not fall out of it’s recessed
groove in the spacer. Install the assembly on the rear
of the engine, ensuring the coolant temp sensor is on
top and the radiator hose outlet is facing towards the
intake side of the engine. Keep it sandwiched tightly
together as you tighten the bolts to 16 ft-lbs.
Figure 18.
Figure 18
19) Install the heater hose to the heater barb on the
spacer. Install the reroute radiator hose in the newly
installed thermostat outlet and route hose to the
radiator. Figure 19.
Note: The reroute radiator hose will need to be
trimmed to fit at the radiator end for 1994-1997
applications.
Figure 19
20) Remove the EVAP canister by sliding it upward off
the bracket. Install the provided hose support bracket
using an M6 Bolt and nut as shown. Slide the EVAP
canister back into the housing. Install a P-clamp in
the bracket as shown. A/C equipped vehicles will
have a relay bracket at the location indicated in
Figure 20. Remove this bracket (if equipped) and
secure the relay out of the way with a zip-tie. Install a
P-clamp as shown using an M6 bolt.
Figure 20

Part # 910-850 910-855 -7- Modified 03/18
Installation Instructions
21) Attach the spill-free funnel if you have one. Fill the
cooling system slowly while watching for coolant at
the coolant temp sensor. Continue filling until all air
has bled out of the coolant temp sensor hole, then
torque the sensor to 20 ft-lbs with a 19mm deep
socket. Figure 21. Continue filling radiator until full
and check for leaks. Top off coolant overflow tank. If
you have a cooling system pressure tester, pressure
test now to ensure there are no leaks.
Figure 21
22) Fit the new EGR tube behind the engine, apply
anti-seize to the EGR tube threads on the exhaust
manifold and thread the large tube nut on loosely.
Leave the other end of the EGR tube loose at the
intake manifold. If you tighten down the EGR tube
at this time it will be difficult or impossible to install
the lower bolt for the coil bracket. 910-855 does not
include this tube.
23) Install the two-wire coolant temp (ECM) connector.
Install the special cam sensor retaining bolt and
tighten to 16 ft.-lbs. Connect the one-wire coolant
temp sensor wire to the sensor.
24) Reinstall coil bracket to rear of engine. The lower
bolt must be replaced with the provided button head
bolt for EGR tube clearance. Install with a 5 mm allen
wrench. 910-855 does not include this button head
bolt. (Optional) The coil bracket can be modified to
greatly ease future removal and installation if desired.
Remove the coil bracket from the vehicle. Lubricate
the rubber bushing with silicone spray. Remove the
metal sleeve and carefully pry out the rubber bushing
with a flathead screwdriver. Figure 24.1. The rubber
is old and easily damaged. Grind out the fork as
shown so that it will easily slide down onto the rubber
bushing, Figure 24.2. Insert the metal sleeve back
into the rubber bushing and install on the back of the
engine using the provided button head bolt.
Figure 24.3.
Ensure that the bushing is oriented correctly. The
raised part of the bushing shown in Figure 24.4
should be facing down so it does not contact the fork
on the coil bracket. Install the coil bracket on the rear
of the valve cover by simply sliding it down onto the
bushing and then tightening the two easily accessible
bolts into valve cover. Figure 24.5.
Figure 24.2
Figure 24.1
Figure 24.3

Part # 910-850 910-855 -8- Modified 03/18
Installation Instructions
Figure 24.4
Figure 24.5
25) Install and tighten the two 10mm nuts securing the
EGR tube to the intake and then the large tube nut.
Reinstall the exhaust manifold heat shield and the air
filter box. Reinstall the harness for the Mass Air Flow
Sensor.
26) Reconnect the oxygen sensor and Camshaft Position
Sensor harnesses. Figure 26.
Figure 26
27) Reconnect the vacuum line for the brake booster at
the intake and install the two 10mm bolts holding the
metal vacuum line in place.
28) Reinstall the air intake tube, PCV breather hose and
IAC hose.
29) Start engine. Run vehicle at idle with radiator cap
off (or with funnel attached) to bleed any remaining
air from the cooling system. Do this with the front of
the car still elevated on jack stands to help trapped
air make its way to the radiator filler neck. The new
upper hose will suddenly become warm to the touch
when the thermostat opens. Once this happens
any air trapped behind the thermostat will be pulled
through the hose into the radiator. Once the upper
hose becomes warm, install radiator cap. Check/reset
ignition timing to factory specs 10 deg BTDC. Timing
must be checked with all loads off, vehicle idling at
full operating temp, and check connector shorted
from TEN to GRD. Timing must be set correctly or
severe engine damage may result! Consult service
information if further information is required.
30) Test drive vehicle while closely monitoring
temperature and re-check for leaks. Allow engine to
fully cool down overnight and recheck that radiator
and overflow tank are full. Top off as necessary and
enjoy your cooler running Miata!

Part # 910-850 910-855 -9- Modified 03/18
Moss Europe Ltd.
Hampton Farm Industrial Estate
Hampton Road West, Hanworth Middlesex, TW13 6DB
In the UK: 020-8867-2020 FAX: [phone]
Moss Motors, Ltd.
440 Rutherford Street, Goleta, California 93117
In the US & Canada Toll Free [phone]
LOCAL [phone] FAX [phone]
Although every effort has been made to ensure the accuracy and clarity of this information, any suggestions
that you may have that will improve the information (especially detailed installation notes and photos) are
welcome. These instructions were developed and written by Moss Technical Support. If you have any questions
or difficulties with your installation of this product, telephone [phone] between 7:00 a.m. and 4:00 p.m.,
Pacific Time for assistance.
Installation Instructions
910-850, 910-855 Bill of Materials
Item No. Description Quantity Unit of Measure
772-910 SPACER, COOLANT REROUTE 1 EACH
772-913 WATER NECK, COOLANT REROUTE 1 EACH
910-851 HOSE,COOLANT RE-ROUTE 1 EACH
051-132 HOSE BARB, 3/8 NPT X 5/8 1 EACH
051-203 PLUG, PIPE, 1/8 NPT, HEX HEAD 1 EACH
772-911 PLATE, COOLANT BLOCK OFF 1 EACH
051-860 BOLT,HEX FLANGE,M8 X 1.25 X 16 2 EACH
051-730 BOLT,HEX FLANGE,M8 X 1.25 X 50 1 EACH
771-330 BOLT,HEX FLANGE,M8 X 1.25 X 75 1 EACH
999-023 GASKET/T-STAT 160 DEGREE 3 EACH
772-956 TUBE, EGR, COOLANT REROUTE (NOT IN 910-855) 1 EACH
051-810 P-CLAMP, 1.625IN. ID 2 EACH
772-947 BRACKET, HOSE 1 EACH
051-004 BOLT, HEX FLANGE,M6 X 1.0 X 16 2 EACH
051-787 NUT, HEX FLANGE, M6 X 1.0 2 EACH
052-947 BOLT,BHCS,M8X1.25X25,ZINC (NOT IN 910-855) 1 EACH
051-074 WASHER, FLAT, M8 1 EACH