HLA noise & diagnosis

Some HLA noise during cold startup is quite normal. During shutdown, 24 HLAs are in varying degrees of compression depending on where the 4 cams stopped at shutdown. Those HLAs experiencing the greatest compression from the cam-lobe (175lb/in spring) will take a correspondingly longer to pump-up at a cold-start compared to their less compressed counterparts. This HLA pump-up time is further compounded by the time elapsed between starts, and to a lesser extent dependent on where the HLAs is on the oil path - HLAs at the top left of the rear bank (cylinder #1) taking slightly longer. The use of centre-oiled cams (as favoured by Porsche in race engines over spray-bar systems) helps to ensure fast targeted oiling in both cold start & high-rpm conditions until ~430bhp is exceeded. After ~430bhp spray-bar lubing is required despite superior centre-lubed cams to avoid harmonic related fractures.

Oil changes must be regular, with oil level regularly checked to avoid a low oil condition resulting in aeration of oil. Factory oil filters are around 4$US and ?5.70 (UK Mazda Main Dealers).

Actual mechanism of HLA noise is a function of the degree of lash between the cam lobe and HLA surface. When HLAs are pumped up with clean oil & operating correctly they maintain lash at zero for all rpm (so achieving the self-adjusting maintenance-free operation of HLAs). Some HLA noise is often not from the HLAs but from a friction-gear used to reduced backlash noise from the two cam-drive helical-cut gears on the camshafts - for aesthetic noise reasons. Oil cleanliness has a direct bearing on HLA & Friction-Gear noise - as well as the acoustics of reflection of noise from the oil's surface in the oil pan. Hence after an oil change engines may be quieter.

Automatic (ATX) Gearbox Critical Maintenance

• The primary cause of automatic gearbox failure is due to insufficiently frequent oil changes & overheating.
• ATX oil (ATF) breaks down faster with each rise in oil temperature, and rapidly above 125oC. ATX gearbox oil is continually contaminated by the circulation of clutch-pack abrasive particles throughout the gearbox.
• Factory change intervals at 600hrs (24,000 miles at 40mph average) are twice as long as the 300hr high temperature service life of ATX oil.

Mazda Factory-Remanufactured Automatic (ATX) Gearbox

A factory remanufactured unit is available from discount Mazda Dealers such as www.trussvillemazda.com. Their benefit is that factory parts such as new cases are used if the original is out of spec, and the considerable design improvements from 1993-2000 are implemented. If sourcing a gearbox from elsewhere, ensure all updates are performed so you gain the (greater) reliability of the 2000 gearbox and enquire whether updated parts are available (stronger torque-convertor & Raybestos Blue clutches for example). Annual oil changes should be effected on any Probe/Mazda automatic gearbox as their cost vs repair is minimal. Sandwich Plate Design

Upgraded Automatic Gearbox Parts

Upgraded parts for reliability & performance such as torque-convertors, clutch-packs, oil-pumps are available from Level-Ten.

Notchy Manual (MTX) Gearboxes

The correct all-temperature gearbox oil weight is 75w90. A GL-5 oil can only be used if it does not contain sulphur. Only one GL-5 oil in the UK at the time of writing does not contain sulphur, thus it is best to telephone the manufacturer of the oil using the number of the reverse of the bottle. The use of a gearbox oil which does contain sulphur will halve the life of the synchros & bearings as they are of a bronze/brass construction. The reason is that sulphur (eg, manganese sulphonate) becomes acidic. Hence, Mobil1 75w90 GL-5 is NOT suitable for Mazda gearboxes as Mobil confirm.

Notchy shifting is common place during cold mornings and can be corrected by changing the oil to Full Synthetic Redline MT90 75w90 GL-4. Notchiness is due to synchros requiring an opposing viscosity of oil to differentials, yet both must share the same oil. Thus manual gearbox oil must not only cover both synchro & differential requirements, but do so over all encountered operating temperatures. Non-synthetic oil cold weather viscosity prevents synchros operating properly. Some manuals list ATF as an appropriate oil - this is incorrect. Engineering tolerances for ATF v 75w90 gearbox design differ. A synthetic gear oil provides better gear-teeth protection & lubrication, reduces transmission losses during warmup so aiding the environment regarding emissions & fuel usage.

Some notchy shifting may be due to a non-disengaging clutch, either through wear or use of non-OEM parts (eg, ACT which require adjustment).

Power Steering Oil

Redline D4ATF Synthetic ATF reduces steering effort on cold mornings, reduces steering wear and increases temperature protection. As per the manual, holding a steering wheel at lock even for 5 seconds can overheat the fluid which destroys its lubricating properties and wear increases. Replacement is easiest by the fractional dilution method, using 2Q of (ideally) synthetic fluid: syphon old fluid out of the reservoir, replace with new, drive the car & repeat again until all 2Q have been used up. Thus the old fluid is diluted 1:1 1:2 1:4 1:8 1:16.

Coolant

Maintenance interval is 2yrs/24k miles, however coolant turns acidic within 9 months thus annual replacement is advised in light of a galvanised steel pipe running the width of an aluminium engine. Mixing aluminium & steel in a cooling system results in galvanic depletion of the coolant in under a year and scale deposits in engine heads can cause head cracking, hot-spots that modify ignition deflagration and elevate top-end wear. It should be noted that corrosion does not affect the stainless-steel head gaskets.