Three joints.
One casting.
The 1500’s water-pump housing joins the engine, the separate pump, and the thermostat outlet. This guide shows which joint each gasket and fastener belongs to. The virtual casting identifies these parts, but the position and orientation of its engine and pump mounting faces have not been verified. The 3D shape cannot yet show real bolt access or joint spacing.
Housing to head
Gasket 138702 has two coolant openings and three bolt holes. Three housing bolts have different catalogue lengths. The real casting decides their positions.
Pump to housing
Gasket 138701 seals the round impeller opening. Three separate studs and nuts hold the pump flange. These are not the housing-to-head bolts.
Thermostat assembly
Factory plate B92 item 8 lists the thermostat separately: GTS104 at 82°C, or GTS106 at 88°C for cold climates. The separately selectable CAD thermostat is a recognition reference. The public reference’s 54 mm flange, thickness, projections, cage, bridge and seating station are estimates, not supplier specifications or measurements of this car. The estimated flange overlaps the estimated pump-housing seat; the model reports that conflict instead of cutting an invented recess. The housing worksheet now accepts independent recess diameter, joint-plane-to-floor depth and throat diameter only after confirming a coaxial circular seat normal to that plane. All three are required for an owner recess; partial readings remain notes. This never sizes the seat from the thermostat or moves the thermostat onto its floor. Read the seat measurement method ↗. Spring, bleed feature, opening motion and temperature calibration remain omitted.
During a planned cold opening, photograph the actual thermostat marking, orientation, bleed feature and seat before lifting it. Measure flange diameter and thickness, projections above and below the bearing face, seat diameter/depth and gasket opening independently. Keep those observations with the housing number and original gasket stack. The factory alternatives do not identify the fitted thermostat or prove its operating temperature. The CAD worksheet now records flange diameter and thickness, lower projection from the lower flange face and upper projection from the upper face independently. Confirm those actual faces before saving direct dimensions. A separate owner build can use those outside readings; its installed station and internal profiles remain estimates, and the model reports conflicts without changing the readings. Read the measurement and build method ↗.
IMG_6895 shows the upper outlet’s filler plug and a raised marking that appears compatible with CHA343. This is a tentative photo reading, not a confirmed identity for either casting. Compare the source and capture the complete number ↗. It does not identify the lower pump housing or settle the 1975 modification history.
The outlet uses a separate GTG103 gasket and two screws in the factory parts list: CHA440 at 1¼ in and CHA441 at 1 in. Their positions on this car and its 1975 outlet variant still need identification.
The current hex-head screw references measure catalog length from the modeled underside of the head to the tip, passing through the separate washer. This corrects a model gap at the washer; it does not verify the actual head form, washer, fitted hole assignment or threaded engagement. The outlet worksheet’s long/short screw readings remain notes until their identities and positions are established. During planned removal, identify each head form first. For a protruding hex head, measure from its underside to the tip; keep a countersunk or other head and its length convention separately identified. Keep each washer separate and record the screw’s original hole. Read the model datum correction ↗.
Lower-hose inlet and tapped ports
The 144297A replacement-casting photograph makes the long lower-hose neck and two tapped bosses clear. IMG_6895 shows a lower hose, clamp and wired fitting on this car, but does not expose the complete casting or the second port. The 3D housing now includes those features for identification. The neck’s roughly 34 mm outside diameter and 47 mm projection are scaled from the oblique supplier image; neither is a verified fitment measurement.
During planned access to the lower outlet, measure the retaining bead’s widest outside diameter and its full raised width along the neck axis, separately from the straight neck. Photograph the exposed tip with a scale and record any bead setback. The housing inspector now applies direct bead diameter and width to a separate owner STEP and its hose relief. The bead contour and flush-to-tip station remain estimates; clamp location, hose insertion and seal fit are not established by those two readings.
Identify the fitted casting before matching a replacement. The factory-era 144297 housing is listed as cast iron, while 144297A is an alloy replacement in the Triumph-family parts catalogue. A used-parts supplier describes a 144297 casting stamped 307589; that is a mark to look for, not proof that every original casting carries it. The eight-view 144297A listing shows the pump opening, two-passage engine flange, hose neck and thermostat end from different angles. IMG_6895 does not reveal a readable casting mark or establish whether this car’s darker housing is iron or alloy. Photograph the actual mark and inspect an accessible bare spot before selecting parts; paint and grime make color unreliable.
Before ordering a hose, clamp, sender or adaptor, record the casting mark and photograph the neck, both tapped ports and every attached fitting with the engine cold. Measure the metal neck outside the bead and the lower hose outside diameter on a straight section. Measure its relaxed bore only if the hose is already removed during planned work. The 3D inspector can use these direct readings and the neck's exposed shoulder-to-lip length in a separate owner STEP build; it keeps the unmeasured shoulder, neck direction and hose bend provisional. Keep the upper and lower hose routes distinct; the 3D study shows only the visible engine-end bend, not the unseen radiator connection.
The 3D study now shows the visible lower-hose bend and housing-end clamp separately. IMG_6895 and IMG_6896 support the downward turn beside the fan. The hose stops before the hidden radiator connection; its 43 mm outside diameter, 35 mm bore, bend, clamp and clearances are model estimates. Photograph the entire hose from both sides before ordering one or planning its removal.
The protected line in IMG_6895 appears to be a capillary temperature-gauge connection. That fits the Moss instructions for Midget 1500 gauges through 1977: they name the 11K2846 / 361-065 adaptor and AED172 / 324-805 copper washer for a capillary bulb. The 1500 cooling list assigns the later electrical sender to chassis 200001 onward (1978). The 3D model now separates the comparison adaptor, washer and short bulb/nut end. Confirm the actual gauge and line on this car before buying a sender or loosening the fitting; the model does not establish its thread or the line’s route to the dash.
Recognize the lower clamp drive
IMG_6896 gives a clearer view of the lower hose clamp’s external hex drive and perforated band. Locate the drive in the owner photo ↗. The current CAD clamp reference now uses six external flats in place of the old round drive barrel. Its slotted cue remains a recognition estimate; the precise recess standard, AF size, head dimensions and clocking still need a direct inspection.
The change retains the previous estimated corner diameter, axial extent and station. It does not select a wrench or socket, establish clearance past the fan or belt, or verify a release/removal path. Photograph the actual head from another direction, copy any band markings and measure opposite flats and band width directly when safely accessible during planned work. Keep those observations with the installed clamp and source photo. Do not infer a driver size from the band slots or the virtual hex.
Measure each outlet screw separately
During planned removal, keep each screw and washer indexed to its original hole photograph. The long-reference screw inspector and short-reference screw inspector now accept independent under-head length, opposite-flat hex width and head height after you confirm a protruding hex head. The catalog names are reference labels; they do not identify either fitted screw or its original hole.
Measure length from the head’s bearing underside to the tip, excluding the head and loose washer. Measure hex width between opposite parallel flats, not corners, and head height along the axis from underside to top. Name the actual screw, hole, photograph and measuring method in the source note. For another or uncertain head form, keep its readings in the note rather than confirming a hex head to make the model accept them.
A separate owner build changes only the selected screw’s envelope. The modeled under-head plane and washer stay fixed; the two lengths are neither sorted nor exchanged to fit the catalog names. The older housing-level long/short fields remain notes and are never promoted into these selected-part inputs. Shank diameter, threads, engagement, washer geometry, fitted station, clamping and access still need evidence. Read the supported inputs and limits ↗.
The three housing bolts
The Moss Europe Midget 1500 cooling drawing, printed p. 136 numbers the bolts 14–16. Its facing list gives one of each length, all 5/16 UNF with GHF332 spring washers. The diagram below is a face-on checklist of the photo-scaled 138702 gasket, not a view of this casting installed in the car. The drawing’s oblique left/right assignment needs checking against the real housing.
Rimmer’s photograph of a used 144297 housing is a useful second view: it shows the two coolant passages and three bolt holes on the engine joint, while the large round pump opening is on a separate face. The long hose neck, thermostat seat and fittings are visible in the same image. It establishes how to identify the joints when the housing is off the car, but perspective prevents a trustworthy face angle, center offset or bolt-access measurement. Its fittings also should not be assumed to match this car.
| Moss item | Catalogue part | Nominal bolt length | What to verify on the car |
|---|---|---|---|
| 14 · upper | BH605221 | 5/16 UNF × 2¾ in (69.85 mm) | Which upper hole, washer and actual under-head length |
| 15 · drawing left | BH605191 | 5/16 UNF × 2⅜ in (60.33 mm) | Installed side, washer and actual under-head length |
| 16 · drawing right | BH605181 | 5/16 UNF × 2¼ in (57.15 mm) | Installed side, washer and actual under-head length |
Check the alternator link at item 16: the Moss Europe alternator list also calls BH605181 the link-to-thermostat-housing bolt. The two listings may describe a shared fixing or separate bolts of the same specification. Trace the fitted link and compare IMG_6889 ↗ before treating this joint as an isolated housing bolt; neither catalog page proves the installed stack.
A trial bolt placement through the current virtual housing intersected the virtual pump. The used 144297 photograph, multi-angle 144297A replacement photos and Moss exploded drawing establish two distinct mounting interfaces. They do not establish the angle between their machined planes, their relative rotation, or their center offset. The current STEP assumes parallel planes and places the patterns so a trial housing bolt crosses the virtual pump. That placement is known to be wrong; parallelism itself is unverified. Neither photographed casting is confirmed as fitted to this car. The STEP leaves out the three bolts because false placement would misrepresent access and fit.
The two-screw thermostat outlet
The factory 1500 cooling parts plate lists one GTG103 gasket, one CHA440 5/16 UNF × 1¼ in special screw, one CHA441 5/16 UNF × 1 in special screw, and two WL208 lock washers. It also lists different outlet castings for North American cars around the 1975 cooling change. The fitted casting and which ear uses the longer screw have not been confirmed.
The GTG103 ruler photograph suggests a central opening near 49 mm and bolt centers near 70.5 mm apart. These are approximate photo readings. The 3D study now shows the separate gasket, two ears and both screws so you can identify the joint; the actual casting faces, bolt assignment and tool clearances still require a square-on photo or direct measurement.
The current outlet model omits its former small opposite-side neck and cross-bore. Those features came from an uncertain interpretation of the smaller hoses in the owner photos. IMG_6895 and the factory manifold plate require keeping the upper outlet distinct from the water-pump body and its separate manifold/heater adaptors. This correction does not identify the fitted casting or prove that it lacks another branch. The 1975 bulletin shows modified CHA595 plumbing; photograph the complete upper casting and trace each small hose to its actual attachment before adding a variant-specific connection.
Compare a loose replacement with the actual outlet. IMG_6895 shows a filler plug in the top of this car’s upper casting. A plain Spitfire-style elbow without that opening is visibly different; Moss lists the plain 835-555 elbow for Spitfire and TR250/TR6 applications. A similar two-hole flange does not establish equivalent hose direction, filler arrangement, thermostat seat, small branches or mounting stack. Ask for the replacement’s markings and both faces, then compare the complete fitted cooling configuration before ordering. No current photograph establishes that this car’s outlet needs replacement.
The filling point now has separate plug and seal references. The factory plate lists ARA2634 and TRS1418 separately. The dark hex-headed study follows the visible plug more closely than the old round gold marker, but its dimensions, smooth shank and bearing face remain estimates. The actual seal is hidden in the owner photos; the ring section and seating shown in CAD are unverified. During planned cold access, photograph and measure the actual plug, seal and groove separately before choosing replacements.
Plan a pump or housing replacement
The Triumph Toledo factory manual, operations 26.50.01 and 26.50.03, documents a related engine-family service order: drain coolant and remove the belt before separating the pump’s three nuts from the housing; a housing removal also releases hoses, the thermostat outlet, small pipe connections and three engine-side bolts. A Midget 1500 owner’s repair account independently describes three pump fixings and corroded outlet screws. These sources establish a planning checklist, not the exact 1975 North American Midget procedure or a measured withdrawal path.
- Identify: With the engine completely cold and key out, photograph the fan, belt, pump, housing, coolant fittings and every hose branch. Record the housing mark and whether the fan or pump arrangement has been changed. This car’s photographed fan tips need a direct damage check before any running test.
- Before disassembly: Obtain the Midget factory instructions for the fitted cooling configuration. Plan coolant collection, hose identification, belt slackening and access around the radiator and fan. Note every small pipe and the protected temperature-gauge line; the line in IMG_6895 may be capillary and must not be treated as an electrical sender wire.
- At the pump joint: Identify the three separate stud-and-nut positions and gasket 138701. Record pulley and fan arrangement before removing anything; the related manual removes pump, pulley and fan as a group, but this car’s clearances are unmeasured.
- If the casting also comes off: Label each engine-side bolt by its actual hole and under-head length. Keep the three lengths and any brackets or washers indexed. Document the thermostat and pipe connections, both gasket faces and casting mark before cleaning.
- Before refitting: Match replacement gaskets and hardware to the removed parts and the Midget manual; inspect threads and mating faces. After assembly, follow the fitted-system fill and leak-check procedure and verify belt alignment. The virtual assembly does not supply torque, sealant choice or a safe fan-to-radiator withdrawal clearance.
What would make the CAD faithful
Record these during a planned housing repair. The 3D inspector has fields for the smaller angle between the machined planes (0° if parallel, 90° if perpendicular), center offsets, and each bolt length; those entries are observations until a measured owner build uses them.
- Before loosening: Photograph the complete housing, thermostat outlet, pump flange, hoses, brackets and all visible fastener heads with the engine cold.
- Keep positions: Label each of the three housing-to-head bolts by its actual hole, then record any shared bracket and washer. Do not mix the different lengths.
- Measure the casting: Photograph both machined gasket faces square-on with a ruler. Measure the smaller angle between their planes, including 0° if they prove parallel; record which way the pump face points relative to the engine face. Record left/right, up/down and fore/aft offsets from the centroid of the three head-side bolt holes to the pump-opening center with the casting held in its installed orientation.
- Record the patterns: Measure all three hole centers on each joint, gasket thicknesses, casting marks, hose neck sizes, and the thermostat seat relative to the pump seat.
Source trail
Moss Europe Midget 1500 catalogue, printed pp. 136–137 ↗ provides the exploded relationships and bolt list. Rimmer’s used 144297 housing photograph ↗, its 144297A alloy replacement photograph ↗, the eight-view alloy listing ↗ and Paddock’s second alloy view ↗ show casting topology, without usable scale or proof that either photographed casting matches the one fitted here. The 138702 gasket photo ↗ and 138701 gasket photo ↗ inform the separate face outlines. The owner photographs establish only the visible assembled arrangement.