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ZF Gearbox fluid leak?


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It never rains but it pours!! haven't had any issues with my Response for years and now a couple of things rear their heads.

I've just noticed a worrying amount of oil/fluid in the bilge, first time this has happened and as it's mixed with a bit of water it's hard to tell whether it's engine oil or transmission fluid. Almost impossible to tell where it's coming from, although the only signs of misplaced oil is around the gearbox, the engine/sump appears completely clean in all the places a leak might occur. The fluid levels in engine and GB are both still OK and so it's not a huge leak at the moment.

Does anyone have knowledge of the ZF box in so far as where a leak might occur? What sort of job is it to take the box out if required? The boat's only done approx 250hrs and so it's a bit disappointing to have a fluid leak at this stage.

Any advice greatfully accepted!!

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@Timmo:  make sure you eliminate the dipstick as a source before pulling it out.  Input / output seals tend to be culprits when it comes to leaks.  Also, verify it is not any of the pressure sensors (oil pressure / warning sensors).  Can be challenging to pinpoint a small leak, windage and airflow can move small amounts away from source.  Sometimes you can do a temporary 'diaper' install to locate a leak before you tackle the wrong source.

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1 hour ago, Woodski said:

@Timmo:  make sure you eliminate the dipstick as a source before pulling it out.  Input / output seals tend to be culprits when it comes to leaks.  Also, verify it is not any of the pressure sensors (oil pressure / warning sensors).  Can be challenging to pinpoint a small leak, windage and airflow can move small amounts away from source.  Sometimes you can do a temporary 'diaper' install to locate a leak before you tackle the wrong source.

I probably blamed the gearbox prematurely before I conducted a thorough investigation. The reason I focused on the gearbox was because I could find no signs of oil on the engine anywhere, under the sump, around the front/rear seals, rocker covers etc. Not knowing what ATF looked like when mixed with water though I mixed a bit in a jar and it looked nothing like the milky colour engine oil turns when mixed with water which is what was in the bilge and so I then decided it was definitely engine. Not knowing that much about SBC's I googled a few things and nearly had a heart attack when I found out what was involved in changing a rear seal, engine out, sump off??? Correct me if I'm wrong!! Anyway I eventually found the source, one of the items you mentioned, the oil pressure senders. The "manifold" that the sender and switch screw into is connected to the block via a very puny piece of brass tubing, totally unsuitable for the job in my opinion. Where the tube screwed into the block was where the leak was but as soon as I started to take the sender off so that I could unscrew it, the the the whole thing just fell off. On examination it would appear the brass tube had fractured for around half its circumference and putting a spanner near it broke the camel's back. Thank goodness it didn't break off at full oil pressure, would have made a hell of a mess. Am now waiting for the right sized ezy out to remove the bit still in the block and a more sturdy automotive type manifold to be delivered to my local parts store so that I can put it all back together. Just hope the broken off bit comes out OK. I'll post some pictures later to let you have a look at what I'm talking about.

Edited by Timmo
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That's great news!  

Could have been much worse - Glad its just a sender unit and not something more sinister this close to the start of the season. 

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This is another effort at posting this, I messed up the photos first time. The photos are of the original oil pressure sender/switch set up, the new set up I've installed and the reducing adaptor with the broken off piece of brass tubing in it. As I said before, the original set up with the thin walled piece of brass tubing connecting the whole lot to the block is a bit "backyard" for a company like Indmar. Anyway all installed and ready for a test run, hopefully no leaks. One thing I have to remind myself is that a little oil goes a long way and a bit of milky fluid in the bilge doesn't necessarily mean a disaster and finding an oil leak on an engine that's painted gloss black is no easy task.

Once again Woodski was right on the money with his advice to check the sender units.

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Edited by Timmo
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On 3/23/2018 at 5:07 AM, Pra4sno said:

That's great news!  

Could have been much worse - Glad its just a sender unit and not something more sinister this close to the start of the season. 

We do things opposite to you guys down here, probably got another 6 weeks, weather permitting.

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