VW Pathfinder 50 marine diesel questions

[RobertPA]

Hello all. I have taken the liberty of moving a discussion about the VW Pathfinder 50 marine diesel engine from a "Want to buy" thread to this one.

I recently purchased one of these engines, which appears not to have been well maintained, and I am in the process of rehabilitating it. I have the Haynes VW Rabbit diesel workshop manual in hand and the Bentley one on order.

Awhile back a user by the name of delmarrey posted some useful photos of one of these engines that he used to own. I can't tell if he's still on the Cruisers Forum. In any event, I'm curious to know what kind of a temperature gauge sender he had installed on the cylinder head of this engine. In the VW Rabbit version of this engine, the sender connects to a hose running from the cylinder head to the car heater.

On my engine the hose (which used to run to the water pump I believe) has been cut and blocked. See appended photos. The lovely clean engine in these photos is the one that used to belong to delmarrey; the dirty one is mine.

[osprey877]

I have a version of the same engine. On mine, the water temp sensor is blocked off at the rear end of the sensor, as it is in your pic of the “clean” engine. On your engine, the auto hose has been left on and then cut and blocked. Should work either way. The sensor itself is a VW part.

[osprey877]

I’ve looked again at your photo and I think you have the correct sensor in place now, or at least it looks just like mine. There are two electrical terminals on it, one at either end of the cross piece. The wires for it are in the harness from the ignition key/instrument panel.

[RobertPA]

Thank you Osprey for your quick reply. Do you have any idea what VW part that sensor on your engine is? How to ID it in a retail catalogue, etc.? I'm inclined to get one like yours, but where?

[RobertPA]

Osprey, so the sender on your engine looks like mine, and not the one on the clean engine?

[ryangalliford]

Welcome to owning one of these old engines!


Id recommend searching through the VAG catalogs online. The one I often use is 'www(dot)auto-parts(dot)spb(dot)ru/cat/au/au.mycat?SelVh&cl=dr2000'. Use a translator and scroll to the bottom to 'Diesel Industrial Engines', then its likely the 1.5/1.6. Youll find every VW part and option available to use on the engine in one of these old catalogs.


Looks to me like the temp alarm is typically VW 049-919-501. Pathfinder generally used Datcon gauges, and the sender is probably something like 02022, but depends on your gauge at the panel; the range of the gauge needs to align with the range of the sender.


If youre not connecting to a hot water heater, a proper cap at each end might help you sleep at night. I cant tell how the hoses are plugged. On mine, a 1.5 from 1982, the sender is on the side coolant outlet that goes to the heat exchanger/water pump, and the alarm sender is on the rear.


Good luck with the rebuild!

[ryangalliford]

Oh, fyi, the threads on the VW housings are M10x1. Pathfinder often threaded 1/8npt fittings into them; there is much debate on the acceptability of this. You can use any M10x1 threaded sensor/sender though. From VDO for instance...

[RobertPA]

Thank you ryangalliford for that useful information. I was able to navigate the Russian parts catalogue without too much trouble using deepL.com

Here's another photo of the coolant temp sensor at the back of the cylinder head. You can see that the hose has been plugged simply with a piece of old dowelling. On the water pump end, a previous owner has shut it off with a simple plumbing shut-off valve.

You can see also in this photo that the oil pressure sender has been broken off. That's another topic.

BTW, do you know by any chance what the diameter and thread on the Bowman heat exchanger bolts/studs are (attaching to the exhaust pipe). I need the nuts for these bolts/studs. One bolt missing, as you can see in this photo.

I'm 250 km away from the engine at the moment and can't check this in person. I'm planning a test start-up of this engine in the near future and want to ensure I have the basics in place.

[ryangalliford]

Mine are M8x1.25, however Id recommend checking them before ordering new ones. I replaced mine with A286 stainless; certainly consult your manual before deciding what grade bolt to use.


Oil pressure sender should be an easy fix. If your adapter is broken, a 316 stainless version from McMaster can be had to adapt M10 to 1/8npt, and again, likely just a Datcon gauge(mine is 02505).

[osprey877]

Originally Posted by RobertPA

Thank you Osprey for your quick reply. Do you have any idea what VW part that sensor on your engine is? How to ID it in a retail catalogue, etc.? I'm inclined to get one like yours, but where?

I'm confused. You already have the sensor, or at least the photo you attached is showing it, along with the wire connections. It should work as is, but if you want you can remove the piece of hose that is capped off and replace it with a plug. The hose should be attached to an NPT threaded hose barb that you can unscrew from the back of the sensor, then replace it with an NPT threaded plug. You should be able to get the NPT plug in any hardware or plumbing supply shop.
As for VW parts number, I don't know what it is. The source I have used for parts is Parts Place Inc, in Michigan. They have an excellent catalogue on line and if you phone them or email them a picture of the sensor they will be able to tell you if it is a VW part and how to get one.
If you plan on running the engine in your boat, there are a couple of special VW tools you need to get: 1. A special injector wrench socket to remove the injectors, 2. A camshaft locking bar and a Injection pump locking pin, both of which are needed to install/change the timing belt. 3. Optional is a tool for tensioning the idler pulley on the timing belt. These are all available from Parts Place Inc. and are relatively cheap.
Hope this helps.

[osprey877]

Originally Posted by RobertPA

Osprey, so the sender on your engine looks like mine, and not the one on the clean engine?

Sorry, just saw this post. Yes, my sensor looks just like yours, except mine is capped off at the back end whereas yours has the capped off hose attached to it.

[osprey877]

Originally Posted by RobertPA

Thank you ryangalliford for that useful information. I was able to navigate the Russian parts catalogue without too much trouble using deepL.com

Here's another photo of the coolant temp sensor at the back of the cylinder head. You can see that the hose has been plugged simply with a piece of old dowelling. On the water pump end, a previous owner has shut it off with a simple plumbing shut-off valve.

You can see also in this photo that the oil pressure sender has been broken off. That's another topic.

BTW, do you know by any chance what the diameter and thread on the Bowman heat exchanger bolts/studs are (attaching to the exhaust pipe). I need the nuts for these bolts/studs. One bolt missing, as you can see in this photo.

I'm 250 km away from the engine at the moment and can't check this in person. I'm planning a test start-up of this engine in the near future and want to ensure I have the basics in place.

FYI, I notice from your photos that both you and the clean engine are missing the oil cooler that my engine has and which is installed inline with the water hose running from the back of the heat exchanger to the middle of the block. On my engine the plumbing is bent copper pipes, not flexible hose, and there is an inline engine oil cooler directly below the water temp sensor. You may have one in a different location or perhaps isn't needed??

[osprey877]

Originally Posted by osprey877

FYI, I notice from your photos that both you and the clean engine are missing the oil cooler that my engine has and which is installed inline with the water hose running from the back of the heat exchanger to the middle of the block. On my engine the plumbing is bent copper pipes, not flexible hose, and there is an inline engine oil cooler directly below the water temp sensor. You may have one in a different location or perhaps isn't needed??

Ooops, I looked at the photo again and the large diameter water hoses shown on both your engine photos are fresh water hoses, whereas the oil cooler is on the raw water line that should run from the back end of the heat exchanger to the back side of the exhaust riser, assuming you have a wet exhaust. I don't see any of the raw water plumbing in the photos.

[RobertPA]

I will respond to ryangalliford first. The appended photo on the left is what my oil pressure sender(s) look(s) like. You can see better here where it's bust off. It has two senders; the smaller one painted orange with the wire attachment pointing up is what Parts Place Inc. sells. I guess it's the standard sender for the VW Rabbit 1.5/1.6 l diesel.

I figure both the engine hour counter and the oil pressure instrument/gauge were attached to these senders. I append here a photo of the grubby instrumentation panel (it's been cleaned since this photo was taken).


BTW figuring out how the VW Rabbit was marinised would be a lot easier if I could get my hands on a copy of the Pathfinder parts manual. Thus far, it has been impossible to find a copy anywhere.


Lastly, you'll note that the engine has 660 hours on it.

[RobertPA]

I will respond to osprey877 next. I have the Haynes manual in hand, with the Bentley manual on order. I have been rummaging about on the Parts Place Inc. website. Yes, it seems to be a good source for VW Rabbit diesel parts.

This engine was removed from a sailboat about 10 years ago and has been sitting in a sporadically heated garage since that time. The garage was used for automotive repair which is probably where it got some of its dirt from.

Please see appended various photos of the engine that may show better the plumbing. You can see that the hose to the coolant expansion tank on the Bowman heat exchanger has broken off. I can't tell from the Haynes manual whether this hose attaches to the expansion chamber in the VW Rabbit diesel. The other end connects to the cylinder head.

I intend to change the timing belt (all of the belts) on this engine, but first I want to do some basic tests to ensure that nothing serious is bust, and to estimate rehabilitation cost. I plan to (1) pull the injectors and squirt some oil into the cylinders, then hand crank it several times. (2) Then I will do a coolant pressure test (BTW I saw no coolant in the engine oil when I pulled the dip stick). (3) I will try to start it up.

Can you recommend any other preliminary tests to determine whether this engine is worth rehabilitating?