Cat 908M multiple issues

EK701 said: Making slow progress, but it is progress. After many, many hours of scraping, degreaser, and hot water washer, I finally have all the reachable “gunk” cleaned out from the engine bay. In some places it was over 6 inches (130mm) thick! I got the engine oil and filter changed and the hydraulic oil and filter changed. Next up is transmission oil, axle oil, hub oil, and fuel filters. The switch between high and low on the transmission is still temperamental, but I want to see if changing the oil makes any difference. I think the one hydraulic leak is coming from a hose up under the cab. I need to trace that out better, but if it is a hose, that should be fairly easy to resolve. Here is just a small sample of the gunk that was every where, some places with more oil than others. Overall, for a compact machine with over 20,000 hours, it’s in pretty decent shape. So far I am into it about $1500 in parts, oil, and filters (with most of that being Cat oil and filters). Click to expand... That is awesome, keep us posted!

Forgot to add, the engine oil drain plug, hydraulic oil reservoir drain plug and hydraulic filter drain plug are all magnetic and none of them had any metal on them. The hydraulic filter was very dirty.

All that flammable dust mixed with oil must have made that machine a major fire risk, especially around hot engine components.

Changed the transmission oil today. It was pretty low, but no major metal on the magnets. All 3 transmission positions are working and shifting smoothly now, I think they just needed some exercise. The female hydraulic quick connector on the loader wouldn’t lock, but liberal use of penetrating oil got it freed up as well. I was going to change the rear axle oil (and I may still do it), but it looked really clean and it was full. Still need to check the front axle and hub oil. Spent another hour trying to clean the top of the transmission and hydrostatic motor to chase down the leak. I think the oil leak is coming from the top of the hydrostatic motor. Hopefully it’s just a loose fitting or a bad o-ring.

Two separate issues on your 908M (H8801419). Here’s practical guidance based on common failures for this model. Issue 1 – Quick Coupler Lock Inoperative + Leak When Switch Is Activated The skid-steer style hydraulic coupler lock is controlled by a cab switch that energizes one or more solenoids. These solenoids direct oil to the lock cylinder. Most common causes on these machines: • Stuck coupler lock solenoids (very frequent after the machine sits). • Wiring/connector problem to the solenoids. • Actual hydraulic leak in the lines, fittings, or cylinder under the cab/platform when the circuit is pressurized. What to check first (no schematic required):

1. Locate the coupler lock solenoids (typically near the implement valve or under the cab/platform area).
2. Have a helper activate the cab switch while you listen/feel for the solenoids clicking.
3. Cycle the switch rapidly several times. Stuck solenoids often free up this way and the lock starts working.
4. While the switch is held, carefully inspect under the cab for the source of the leak (fittings, hoses, or the lock cylinder itself). Clean the area first so the leak is easier to spot.
5. Check for voltage at the solenoid connector when the switch is activated (should see battery voltage). If the solenoids click and there is still no cylinder movement, the problem is hydraulic (stuck cylinder, internal leakage, or blocked line). If they never click, focus on the switch, wiring, and fuse/relay. A Cat dealer with the serial number can supply the correct ones (commonly in the UENR5406 / UENR5407 / UENR5409 family for the 906M/907M/908M). Issue 2 – High Speed (“Speeder”) Will Not Engage Low ranges work, but high range only flashes the gear symbol briefly then drops back to low. Occasional grinding suggests the high-range clutch or shift mechanism is trying to engage but not completing or holding. Simple checks before needing Cat ET: • Transmission oil level and condition (check hot, on level ground, in the correct range). Contaminated or low oil is a frequent cause of shift problems. • Confirm the high-range switch itself is sending a clean signal (if you have a multimeter, check continuity/voltage while pressing it). • Listen/feel for the high-range solenoid clicking when the switch is pressed (with FNR in neutral and brake applied, as you described). • Check for any related diagnostic codes on the display even if no warning lights are currently on. Grinding + temporary symbol illumination usually points to either: • Insufficient clutch pressure (pump, filter, relief, or internal leakage), or • A solenoid/sensor/calibration issue that the ECM aborts. Changing the transmission oil and filter is a good next step. After that, Cat ET is the most efficient way to read codes, monitor solenoid currents, and view speed/range sensor data in real time. If you can report what you find on the coupler solenoids (do they click?) and the condition of the transmission oil/filter, more targeted advice is possible.

ChrisMafera said: Two separate issues on your 908M (H8801419). Here’s practical guidance based on common failures for this model. Issue 1 – Quick Coupler Lock Inoperative + Leak When Switch Is Activated The skid-steer style hydraulic coupler lock is controlled by a cab switch that energizes one or more solenoids. These solenoids direct oil to the lock cylinder. Most common causes on these machines: • Stuck coupler lock solenoids (very frequent after the machine sits). • Wiring/connector problem to the solenoids. • Actual hydraulic leak in the lines, fittings, or cylinder under the cab/platform when the circuit is pressurized. What to check first (no schematic required):

1. Locate the coupler lock solenoids (typically near the implement valve or under the cab/platform area).
2. Have a helper activate the cab switch while you listen/feel for the solenoids clicking.
3. Cycle the switch rapidly several times. Stuck solenoids often free up this way and the lock starts working.
4. While the switch is held, carefully inspect under the cab for the source of the leak (fittings, hoses, or the lock cylinder itself). Clean the area first so the leak is easier to spot.
5. Check for voltage at the solenoid connector when the switch is activated (should see battery voltage). If the solenoids click and there is still no cylinder movement, the problem is hydraulic (stuck cylinder, internal leakage, or blocked line). If they never click, focus on the switch, wiring, and fuse/relay. A Cat dealer with the serial number can supply the correct ones (commonly in the UENR5406 / UENR5407 / UENR5409 family for the 906M/907M/908M). Issue 2 – High Speed (“Speeder”) Will Not Engage Low ranges work, but high range only flashes the gear symbol briefly then drops back to low. Occasional grinding suggests the high-range clutch or shift mechanism is trying to engage but not completing or holding. Simple checks before needing Cat ET: • Transmission oil level and condition (check hot, on level ground, in the correct range). Contaminated or low oil is a frequent cause of shift problems. • Confirm the high-range switch itself is sending a clean signal (if you have a multimeter, check continuity/voltage while pressing it). • Listen/feel for the high-range solenoid clicking when the switch is pressed (with FNR in neutral and brake applied, as you described). • Check for any related diagnostic codes on the display even if no warning lights are currently on. Grinding + temporary symbol illumination usually points to either: • Insufficient clutch pressure (pump, filter, relief, or internal leakage), or • A solenoid/sensor/calibration issue that the ECM aborts. Changing the transmission oil and filter is a good next step. After that, Cat ET is the most efficient way to read codes, monitor solenoid currents, and view speed/range sensor data in real time. If you can report what you find on the coupler solenoids (do they click?) and the condition of the transmission oil/filter, more targeted advice is possible. Click to expand... Thanks for the input! I have most of the issues solved (see my previous posts), except for a hydraulic oil leak from somewhere on the top of the hydrostatic drive motor.

Merci d'avoir fourni le numéro de série (908M / H8801419). Voici le détail des vérifications à effectuer pour chaque problème : Problème n° 1 – Verrouillage du coupleur rapide défectueux et fuite Test de clic des solénoïdes : Demandez à quelqu’un d’actionner l’interrupteur de la cabine pendant que vous palpez ou écoutez les solénoïdes de verrouillage de l’attelage sous la cabine/plateforme. Vérifiez si vous entendez ou sentez un clic distinct.

• Déblocage des électrovannes bloquées : Si la machine est restée inactive, il arrive fréquemment que les électrovannes se bloquent. Actionner rapidement l’interrupteur à plusieurs reprises permet souvent de les débloquer.
• Localisation de la fuite : Commencez par nettoyer la zone sous la cabine. Tout en maintenant l’interrupteur en position action, inspectez les conduites, les raccords et le cylindre de serrure afin d’identifier la source exacte de la fuite de liquide.
• Vérification de la tension : Débranchez le connecteur du solénoïde et vérifiez la tension de la batterie à l’aide d’un multimètre lorsque l’interrupteur est activé.
• Vérification : Si les solénoïdes émettent un clic et que la tension est présente, mais que le vérin ne bouge pas, le problème est d'ordre hydraulique (vérin bloqué ou conduite obstruée). En l'absence de clic ou de tension, vérifiez le fusible, le relais ou le câblage de l'interrupteur. Problème 2 – Défaillance de l’engagement à grande vitesse (« accélérateur »)
• État du fluide : Vérifiez le niveau d’huile de transmission à température de fonctionnement, sur un terrain plat. Inspectez l’huile et le filtre afin de détecter toute contamination ou présence de débris métalliques.
• Codes de diagnostic : Vérifiez l’affichage de la cabine pour les codes de diagnostic actifs ou enregistrés lorsque le symbole de vitesse clignote.
• Vérification du solénoïde et de l'interrupteur : assurez-vous que l'interrupteur envoie un signal propre et écoutez le cliquetis du solénoïde de gamme haute lorsque l'interrupteur est activé (avec FNR au point mort et frein de stationnement serré).
• Vérification : Si vous entendez un grincement accompagné du clignotement du symbole de vitesse, il est probable que le calculateur moteur interrompe le changement de vitesse en raison d’une pression d’embrayage insuffisante ou d’un défaut de capteur/d’étalonnage. Si vous pouvez nous indiquer si les solénoïdes du coupleur cliquettent et à quoi ressemblent l'huile/le filtre de transmission, nous pourrons déterminer la cause exacte !

Thanks for providing the serial number (908M / H8801419). Here is a breakdown of what to check next for each issue: Issue 1 – Quick Coupler Lock Inoperative & Leak

• Solenoid Click Test: Have a helper operate the cab switch while you feel or listen to the coupler lock solenoids under the cab/platform. Check if you hear or feel a distinct click.
• Freeing Stuck Solenoids: If the machine has been sitting, solenoids frequently stick. Toggling the switch rapidly back and forth several times can often free them up.
• Trace the Leak: Clean the area under the cab first. While the switch is held active, inspect the lines, fittings, and lock cylinder to identify the exact source of the fluid leak.
• Voltage Check: Unplug the solenoid connector and check for full battery voltage with a multimeter when the switch is activated.
• Verification: If the solenoids click and voltage is present, but the cylinder doesn't move, the issue is hydraulic (stuck cylinder or blocked line). If there is no click or voltage, focus on the fuse, relay, or switch wiring. Issue 2 – High Speed (“Speeder”) Engagement Failure
• Fluid Condition: Check the transmission oil level at operating temperature on level ground. Inspect the oil and filter for contamination or metallic debris.
• Diagnostic Codes: Check the cab display for active or logged diagnostic codes when the gear symbol flashes.
• Solenoid & Switch Check: Ensure the switch is sending a clean signal and listen for the high-range solenoid clicking when the switch is activated (with FNR in neutral and park brake set).
• Verification: If you hear grinding accompanied by the gear symbol flashing, the ECM is likely aborting the shift due to insufficient clutch pressure or a sensor/calibration fault. If you can let us know whether the coupler solenoids are clicking and what the transmission oil/filter look like, we can narrow down the exact cause!

DOUAHCHIA said: Thanks for providing the serial number (908M / H8801419). Here is a breakdown of what to check next for each issue: Issue 1 – Quick Coupler Lock Inoperative & Leak

• Solenoid Click Test: Have a helper operate the cab switch while you feel or listen to the coupler lock solenoids under the cab/platform. Check if you hear or feel a distinct click.
• Freeing Stuck Solenoids: If the machine has been sitting, solenoids frequently stick. Toggling the switch rapidly back and forth several times can often free them up.
• Trace the Leak: Clean the area under the cab first. While the switch is held active, inspect the lines, fittings, and lock cylinder to identify the exact source of the fluid leak.
• Voltage Check: Unplug the solenoid connector and check for full battery voltage with a multimeter when the switch is activated.
• Verification: If the solenoids click and voltage is present, but the cylinder doesn't move, the issue is hydraulic (stuck cylinder or blocked line). If there is no click or voltage, focus on the fuse, relay, or switch wiring. Issue 2 – High Speed (“Speeder”) Engagement Failure
• Fluid Condition: Check the transmission oil level at operating temperature on level ground. Inspect the oil and filter for contamination or metallic debris.
• Diagnostic Codes: Check the cab display for active or logged diagnostic codes when the gear symbol flashes.
• Solenoid & Switch Check: Ensure the switch is sending a clean signal and listen for the high-range solenoid clicking when the switch is activated (with FNR in neutral and park brake set).
• Verification: If you hear grinding accompanied by the gear symbol flashing, the ECM is likely aborting the shift due to insufficient clutch pressure or a sensor/calibration fault. If you can let us know whether the coupler solenoids are clicking and what the transmission oil/filter look like, we can narrow down the exact cause! Click to expand... I appreciate the input, but both of those issues have already been resolved.