2018 - GEN4 Oil Pump Replacement (Damaged Sump)

Hello all,

I must be the unluckiest person alive — I picked up a 2018 Prius with only 12,500 miles (UK).

I pulled the car up on ramps to service it and noticed the oil access hatch on the undertray had clearly taken an impact. After removing the undertray, I found the oil pan had sustained significant damage.

I ordered a new pan and removed the old one. Upon closer inspection, the impact had also hit the oil strainer and caused a fracture in the oil pump.

I’m not willing to risk running the vehicle with the oil pump damaged like that, so I’ve ordered a replacement oil pump from Toyota and plan to swap it over.

Does anyone have any information or tips that might help with the replacement? I’m fairly sure the timing cover will need to come off to loosen the sprocket, but I’m wondering if it can be done without removing the cover.

For context, no oil pressure warning light has come on. I’ve inspected the oil and it’s clean with no metallic shimmer. I also cut open the oil filter and found no metal particles or debris.

Realistically, it would probably continue working for hundreds of thousands of miles since it’s still generating oil pressure, but I genuinely don’t think it’s worth the risk of leaving the damaged pump in place.

Pictures attached.

 

Thanks for the replies.

Some interesting information for Prius owners:

A. When pulling the oil pan off, I found a 14mm nut sitting in the bottom. At first I thought, “That’s strange,” and assumed it had been caught in the undertray from a previous repair.

B. After removing the three bolts for the oil pump and pulling on the pump, it came straight out. The sproket nut had worked loose and ended up in the oil pan. I’m not an expert, but I just can’t see how the impact could have caused the bolt to loosen. Even if the sprocket had become misaligned, the chain should have come loose. The chain tension must have kept the sprocket in place, allowing the oil pump to continue functioning. I’ve never seen anything like it.

C. I can confirm that the pump can be changed from underneath without removing the timing cover. This was the video I found as well — very helpful. I used some 3mm stainless wire to hold the tensioner back and made a simple tool to start the chain onto the sprocket of the new pump. I then turned the crank, which fed the chain onto the sprocket. It’s a fiddly job, but it is 100% possible.

D. I’ve now resealed the new oil pan with RTV and will leave it for 24 hours to cure. I’ll report back tomorrow once it’s started.

One thing to look out for: I used Loctite and tightened the nut on the new oil pump. The recommended torque was 30Nm, but personally I felt that was a little inadequate, so I tightened it slightly more.

For context, the job took me around 1.5 hours to complete, although the oil pan had already been removed beforehand.

I also primed the new oil pump with fresh oil prior to installation.

 

Yes — with the pump bolts loose, the method would have been to use a hook to de-tension the chain and then rotate the crank. Running the wire to release the tensioner would have been a bit more fiddly, but still possible in my opinion.

I’m still really stumped as to why the bolt came loose. I clamped the pump in a vice and checked the shaft with a DTI while rotating it to see if it had bent, but there was nothing out of the ordinary.

I also thought the impeller might have been binding against the housing from the impact, causing the nut to work loose, but everything looked perfect.

At this point, I genuinely think it may have been a manufacturing issue, or possibly that the factory torque specification wasn’t sufficient. It would be interesting to know if anyone else has experienced the same thing.

Attached are some pictures of the pump.

The car is now back to 100% after a 20-minute test drive with all areas checked.

12,500 miles from new.

Replaced:

• New oil pump
• New oil pan
• New Toyota oil
• New coolant for radiator and inverter
• New Toyota air filter
• New Toyota oil filter
• New Toyota cabin filter

 

Yes, it must have taken a significant impact to crack the casting.

I work in engineering and precision machining, and for the life of me I cannot understand how the nut could have worked loose purely from impact alone.

However, it will likely remain a mystery, as it’s impossible to come to a definite conclusion.

Hopefully this information will be useful to someone else.