Thermostats and water pumps

Thermostat and Housing
Bellows type thermostats were originally fitted in the earliest of 848cc Minis and 997cc Coopers. However, wax type thermostats soon took over; they were used in all subsequent Minis and also as replacements for the early bellows type. From time to time, the bellows type thermostats are available, but it has to be said very infrequently.

Owners of some cars whose engines were designed to operate with bellows thermostats swear by them (the early 4 cylinder Triumph TR sports cars are a case in point), but the BMC A Series engines in the earliest Minis seem to be at best unaffected by the type of thermostat and are probably better off with a wax type.

Thermostats which opened at different temperatures were traditionally classified as being for temperate, hot or cold climates. This was the case with the Mini up to 1975, with an 82 deg. C thermostat being recommended for temperate climates, 74 deg. C for hot climates and 88 deg. C for cold climates. After 1975 the 88 deg. C thermostat was fitted as standard.

The recommendation for temperate climates such as that of the United Kingdom is always more of a compromise than the recommendations for specifically hot or cold climates, often resulting in the car running a bit too warm in hot summers and feeble cabin heating in the winter. This can be offset if desired by the use of an 82 deg. C thermostat in the summer and 88 deg. C in the winter.

All Models 1959-92
Except 1275cc 1990-92
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
1	11G292	THERMOSTAT, original bellows type, 82 deg. C	1	1959-61, temperate climates; may be replaced with wax type.
	11G291	THERMOSTAT, original bellows type, 74 deg. C	1	1959-61, hot climates; may be replaced with wax type.
2	GTS1104	THERMOSTAT, wax type, 82 deg. C	1	1959-75, temperate climates.
	GTS1102	THERMOSTAT, wax type, 74 deg. C	1	1959-75, hot climates.
	GTS280	THERMOSTAT, wax type, 88 deg. C	1	1959-75, cold climates.
	GTS280	THERMOSTAT, wax type, 88 deg. C	1	1975-92.
3	12G103	HOUSING, thermostat	1	1959-92, all models; except 1975-80, Canada and Sweden.
4	12A408	HOUSING, thermostat, with transmitter tapped boss	1	Some early to mid-1960s 848 and 998cc engines.
5	CAM4044	HOUSING, thermostat	1	1975-80, Canada and Sweden.
6	ADP210	PLUG, thermal transmitter boss	1	For 12A408 thermostat housing.
7	1B3664	WASHER, sealing plug	1	For 12A408 thermostat housing.
8	TAM1005	PLATE, sandwich, thermostat	1	1980-92, Japan.
9	TAM1007	PLUG, sandwich plate	1	1980-92, Japan.
10	TAM1008	WASHER, sealing plug	1	1980-92, Japan.

1275cc Models 1990-96
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
11	GTS280	THERMOSTAT, wax type, 88 deg. C	1
12	PEQ10019	HOUSING, thermostat, without drilled small outlet	1	1990-91, Cooper Rover Special Products and Cooper Carburetter models.
	CAM6117	HOUSING, thermostat, with drilled small outlet	1	Alternative to PEQ10019; small outlet must be blanked off with a cap before use.
PEQ10019 is a housing with an extra, smaller outlet - originally required for the Austin Metro model - which is not used and is therefore blanked off (i.e. not drilled). The original Metro item CAM6117 may be used in place of PEQ10019, but since the small outlet on it is drilled and operational, it must be capped before fitting to a carburetter Cooper.
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
13	12G103	HOUSING, thermostat	1	1991-96, single point injection models.
14	PEQ10010	HOUSING, thermostat, with sensor boss	1	1992-94, Mayfair and Sprite Carburetter models.
15	PEM10036	PLATE, sandwich, with fan switch boss	1	1990-91, Cooper Rover Special Products and Cooper Carburetter models.
16	PEG10002	PLATE, sandwich, without fan switch boss	1	1991-96, single point injection models. 1992-94, Mayfair and Sprite Carburetter models.

1275cc Models 1997 On
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
17	GTS280	THERMOSTAT, wax type, 88 deg. C	1
18	PEQ100650	HOUSING, thermostat	1	Multi point injection models.
19	PEQ100690	HOUSING, thermostat	1	Single point injection (Japan).
20	PEG100030	PLATE, sandwich	1	Multi point injection models.
21	PEG10002	PLATE, sandwich	1	Single point injection (Japan).

Thermostat Housing Fitting Hardware
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
22	GTG101	GASKET, housing and sandwich plate, cork	1/2	Qty. 2 required if sandwich plate is fitted.
	GUG705558	GASKET, housing and sandwich plate, paper	1/2	Qty. 2 required if sandwich plate is fitted.
In theory the two gasket materials are interchangeable, but the cork gasket seems to be preferred by Somerford Mini customers for a simple thermostat housing fitment, whereas the later paper gasket is preferred for a thermostat housing with sandwich plate (applicable for Japan 1980 on).

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
23A	CHS2515	STUD, housing to cylinder head	3	1959-92, all models without sandwich plate except Canada and Sweden 1975-80.
	FHS2518	STUD, housing to cylinder head	3	Canada and Sweden 1975-80.
	51K885	STUD, housing and sandwich plate to cylinder head	3	Japan 998cc 1980-92 and 1275cc carb 1990-91.
23B	FNZ105	NUT, housing and sandwich plate to cylinder head	3	1959-92, all models except 1991-92 injection.
24	PWZ105	WASHER, plain	3	1959-92, all models except 1991-92 injection.
25	DAM7760	BOLT, housing and sandwich plate to cylinder head	3	1992 on, plus 1991-92 injection models.
26	51K885	STUD, housing and sandwich plate to cylinder head	3	Alternative to DAM7760 bolt.
27	PWZ205	WASHER, plain	3	Alternative to DAM7760 bolt.
28	FNZ105	NUT	3	Alternative to DAM7760 bolt.

Thermostat Blanking Sleeve
If the thermostat is removed from the engine to reduce the running temperature, a blanking sleeve must be fitted in its place to maintain the correct coolant flow around the engine; without the blanking sleeve fitted, overheating in certain areas will occur with resultant damage to the engine. If the engine is fitted with a bypass hose, this will also require removal if a blanking sleeve is fitted. This can be done by blanking the unions in the cylinder head and water pump with caps, also listed below. Alternatively, if the water pump is due for replacement anyway, the later water pump without bypass hose facility GWP187 can be fitted.
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
29	11G176	BLANKING SLEEVE, thermostat	1
30	CAM4126	PLUG, bypass hose union blanking	2	Use if thermostat blanking sleeve is fitted.
31	3H2963	CLIP, bypass hose union blanking plug	2

Water Pump
1959-84
Before ordering a new water pump, you must establish which type is fitted to your engine. There are two different types of impeller (or vane) in A Series engine water pump assemblies. In early 1968 a deeper impeller was fitted to increase the capacity of the water pump; different machining work was required on the engine block to allow clearance for the deeper impeller. You should not try to fit the later high capacity pump to an earlier engine. The early, shallow impeller stands out proud of the back of the water pump body by 5/16"; the 1968 onwards impeller stands out by 5/8".

Earlier Mini engines were originally fitted with a cast iron bodied water pump, which was superseded in production by an alloy bodied version in the late 1970s. The cast iron bodied pump had three major differences from the later alloy design:
(i) It has a screw-in adaptor for the bypass hose (on the alloy pump the bypass hose union is part of the main casting). This is the easiest identification point.
(ii) It has a smaller inlet diameter, technically necessitating the use of a smaller diameter bottom hose (in practice the alloy pump type hose usually fits).
(iii) It may be repaired or serviced (whereas the alloy pump is a sealed unit).
Cast iron water pumps are only occasionally available nowadays, as are the parts with which to service or repair them. The majority of Mini engines now wear alloy pumps, as a cast iron pump may be directly replaced by an alloy pump of the correct capacity.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
32	GWP101	WATER PUMP, cast iron, repairable	1	1959-68; may be replaced by GWP132.
	GWP102	WATER PUMP, cast iron, high capacity, repairable	1	1968-77 approx.; may be replaced by GWP134.
33	GWP132	WATER PUMP, alloy, sealed unit	1	1959-68.
	GWP134	WATER PUMP, alloy, high capacity, sealed unit	1	1968-84.
34	8G2570	REPAIR KIT, cast iron water pump	1	1959-68 (shallow impeller).
	8G2675	REPAIR KIT, high capacity cast iron water pump	1	1968-77 approx. (deep impeller).
35	88G446	SEAL, cast iron water pump	1	Included in repair kits.
36	8G733	HUB, pulley, cast iron water pump	1	Included in repair kits.
37	88G618	ADAPTOR, bypass hose	1	Cast iron pumps only.
38	53K1433	SCREW, lubricating point (if fitted)	1	Cast iron pumps only.
39	2K4974	WASHER, fibre, lubricating point (if fitted)	1	Cast iron pumps only.

1985-96
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
40	GWP134	WATER PUMP, with bypass facility	1	998cc, 1985-92. 1275cc, Mayfair and Sprite Carburetter models, 1992-94.
41	GWP187	WATER PUMP, without bypass facility	1	1275cc, Cooper Rover Special Products and Cooper Carburetter, 1990-91. 1275cc, single point injection models, 1991-96.

1997 On
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
42	GWP188	WATER PUMP, without bypass facility	1	1275cc, multi point injection, 1997 on.
				1275cc, single point injection (Japan), 1997 on.

Water Pump Fitting Hardware
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
43	SH605151	SCREW, water pump to engine, long	2	1959-92; except 1275cc 1990-92.
44	SH605101	SCREW, water pump to engine, short	2	1959-92; except 1275cc 1990-92.
45	LWZ305	WASHER, locking	4	1959-92; except 1275cc 1990-92.
46	TAM1180	BOLT, water pump to engine, long	2	1990 on, 1275cc.
47	TAM1178	BOLT, water pump to engine, short	2	1990 on, 1275cc.
48	12A1344	DOWEL, water pump to engine	2	1959-68 (shallow impeller type pump).
	12G2077	DOWEL, water pump to engine	2	1968 on (deep impeller type pump).
49	GUG705555GM	GASKET, water pump to engine	1

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Thermostats and water pumps

SEAL-CAST IRON WATER PUMP. Genuine Leyland

REPAIR KIT-GWP102 CAST IRON WATER PUMP

REPAIR KIT-GWP101 CAST IRON WATER PUMP

WATER PUMP-ALLOY WITH BY-PASS (cast impellor includes gasket)

WATER PUMP-ALLOY-SHORT IMPELLER-'59-'68. 850 & 997cc

USE: GWP134 OR GWP102R

THERMOSTAT BLANKING SLEEVE

STUD-5/16 UNF/UNC x 3'' LONG-ROCKER POST/THERM. WITH SPACER

BOLT-FLANGED-5/16 UNC x 2 1/2''

PLATE-SANDWICH-THERMOSTAT-MPI

HOUSING-THERMOSTAT-SPI JAPAN-'97 ON

PLATE-SANDWICH-NO SENDER-STD MODELS '92-'94 & SPI '91-'96

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