Car was just serviced front to back. The drive home is 150 miles and when I parked the car, coolant was momentarily "leaking" from the center portion of the rear axle. There is an aluminum plate covering this portion of the transaxle and the coolant was coming out of what appears to be a small, oval inspection window and a small amount at the edge of the aluminum plate.

It only leaked after shut off and there was no trail of coolant down the driveway so I'm assuming it wasn't leaking during the drive. It is, 100%, coolant and not transaxle fluid; the amount that came out fairly small...the larger of the two spots was the size of your palm. The engine coolant reservoir is at a normal level and the overflow tank has a nominal amount in it. I thought the overflow tank may drain at the back of the car but it doesn't, it drains right below the tank itself behind the left front wheel. Is there another coolant reservoir where the transaxle is? Any advise would be great before I tackle it or ship it back to the dealer.

 

There are 2 coolant loops on these cars. One of them runs back to cool the rear diff. The cover plate and/or hoses have been known to leak. If you take off the rear pan, you might see additional dried white coolant stains as well as your leak.

 

Thanks volvodrummer. You are correct, it appears to be leaking from this gray plastic plate. When this gray plate is removed, do you know if there is a large amount of coolant lost or anything else to be aware of? It seems like a simple repair and thus, a waste of time to haul it all the way back to the dealer.

 

I don’t know if you’ll be flooded if you remove the cooling plate. I haven’t repaired one , but if it’s not leaking too bad, I would snug all the bolts to the plate a little and run car again.
that said you should post this question over on the Aston DIY (all models) group on F B. There are Aston techs that hang there and would be able to tell you definitively.

 

Since it happened right after a service, I'd be tempted to take it back to the dealer and have them check it out. It could be something simple they overlooked.

 

Have you resolved your leaking diff cover?

 

The dealer has ordered the part (differential cover plate), and I agreed to put it on simply because of the logistics of getting the car to them, downtime etc.

Once the part arrives, I was planning on sharing some info on the part itself plus what the install is like. I am assuming if it isn't common now, may be at some point because we all know how plastic parts behave over time with heat cycling. I'm not sure if this cover plate is replaced during a gearbox service, but as inexpensive as it is, it should be.

 

Hi @johnghini

I would very much appreciate info on the part, the part number and a pic if you could.

Thanks in advance for posting it.

 

[QUOTE=BWings;4951489]Hi @johnghini

Hi I seem to have exactly the same problem with a leak from the cover plate on the rear differential leaking a small amount of coolant. The car has just ran out of warranty I would be grateful if you could let me know how you get on with changing it. It looks like it’s easy to crimp the rear 2 hoses which hopefully would stop all the coolant leaking regards Danny

 

Here's an update:

I received the differential "cover plate" from my dealer (O'Gara). It's easy to see why these can leak. They're plastic for one and we all know how plastic loves heat cycling, and the small diameter, set-in rubber gasket would likely suffer in its ability to seat / seal correctly over time. If you have this leak, I would start by making sure to (gently) torque the attachment bolts and drive the car on multiple long drives to see if this helps; it did on mine...significantly. If you're not using the car frequently, plus have swings in climate, I'm sure you're susceptible to this.

The part is about $225 from the dealer and in my opinion, should be renewed during your gearbox service. It's not an impressive part. In fact, mine seems to have a small warp to it which you can see in the side view photo. When torqued, the part likely flattens out but it looks like the maker could have engineered better cooling fixtures or refined the injection mold process. Anyway, I haven't put it on yet but was told you will lose about 3 quarts of coolant when removing it. That seems like a lot but we will see. When I replace the part, I will post my experience. As a side note, I am having this plate machined in the hops of making a better part. I'm sure the OEM part is fine, but a beautiful, accurate and more robust part appeals to me. I will post on this when done as well.

 

Hi @johnghini

Thanks so much for posting this. I would like to see what you come up with on a machined replacement. Please keep posting updates...very grateful!

Best,

 

Food for thought. I would avoid machining. Plastic flexes anyway and a little torque might get a better seal. Now if you wanted to fabricate a plate from aluminum or steel, coooool!
Or CARBON Anyway glad you are updating this post. It certainly is pertinent to us all!

 

Thanks Stwsam. You are correct...I intend on machining from Aluminum. We have a lot of fabrication and engineering expertise so it's relatively straightforward.

 

Good info and thanks for sharing! I do wonder though if the plastic material was chosen because it would conform to changes in the surface over a wide range of operating temps and heat cycles? I wonder if an aluminum cover would do the same?

Let us know how you get on replacing it as the book states that the rear subframe has to be dropped to do the repair? Looks like there's enough room without if the bolts can clear the lines.

 

Can't wait to see your finished item. I see a future aftermarket product in your future!