I've been having a slow coolant leak for a couple months and I can't see to find it. It's been pooling to the right and left of the water pump on the block (just below the heads which is why I think I had smoke in the engine bay coming back from Platte River Grill) ). It's also been running down along the oil pan on both sides. It seems to leak until the radiator is 2/3 full and then it stops leaking. I've checked hoses and none of them seem to have any coolant dripping from them. Any suggestions or tests to narrow this down would be great. Thanks!

Thermostat gasket or hoses. Can be head gaskets too.

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I had a pesky leak on my TDI I couldn't track down. Borrowed a pressure test kit and bore scope from Autozone to find them. Would recommend that as well, just not sure what connections you have available to add pressure. To test the system post repair, I actually hooked my bike pump to a small overflow connection on the radiator and plugged the hose that came from there. That worked great, but I don't know if you have a similar connection. About 15psi is all you need.

Thanks guys. I’ll post up after I pressure test.

Pressure test will help find it. It can be a bit tricky if it is only leaking when the truck is running or the system is hot. We just replaced the water pump on TFB, it didn’t show up on a pressure test, but when I pulled the belt the shaft had lateral play and the weep hole was showing signs of the leak.

I rented the kit today. I haven’t looked at any videos yet but I’ve got 3 basic questions before I run the test:
1. Should I top off the radiator?
2. Should I run the engine to circulate / warm the coolant
3. Any other advice

Yeah, top off the rad because you say it seems to stop leaking at a certain point. You could just add distilled water in for now instead of potentially wasting coolant??

The thermostat will have enough bypass to allow the whole system to pressure while cold.

15+/- psi is enough. Shouldn't need to go higher. If you can't readily find the leak, leave it pressurized for a while until perhaps it will start puddling.

If still no leaks, check the oil. Hope it's not milky!

Thanks. I rented the tool and it worked okay (the gauge didn't work). But I got enough pressure in to start the leaks. It looked like it was coming form the sides of the water pump gasket on both driver and passenger side. There might be a little coming from the thermostat gasket.
Plan of action ideas:
1. Replace WP gasket and Thermo gasket
2.) Replace WP , WP gasket and Thermo gasket. How can you tell if a water pump needs replacing?
3.) Something else to try that would be easy....

I wonder if the new radiator had anything to do with it...

How old is the WP? They’re relatively inexpensive and I’d be inclined to just replace it while you’re doing the gaskets since it’s a pain in the ass to change.


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I kept all the hoses connected and removed the front dresses so I could see where the leak was coming from. It appeared that the leak was not coming from the water pump gasket but between the timing cover and the block. I’m assuming I will have to pull the harmonic balancer, drop the pan and get a gasket and seal kit for the timing cover. I did check the oil a little bit ago and it didn’t seem to have coolant in it but I’ll check again today. Any advice before I get started?

I got the harmonic balancer off , timing cover off and oil pan off. All the bolts came out easy (some too easy). No coolant in the oil pan. It was pretty clear that the coolant was leaking right by the passages. I ordered a new gasket kit ( with seal). I’ll grab some new bolts at Ace and start reassembly. When get the gaskets I’ll post up some rtv questions.

Were the bolt threads worn or were they loose because the threads in the holes are worn?

When we rebuilt the block I was able to clean and reuse the bolts. They were already a little worn so this time I'll put new ones in.

Are ya done yet?

yeah yeah yeah Johnny....

I got all the gaskets and seals. I'm finishing up cleaning all the parts before install.

1. I noticed I might be missing a sleeve on the timing belt cover. You can see in the pic that there is one on the passenger side but not the driver side. I wonder if that is a big deal? If so, where in the hell do you get one of those....

2. The water pump (less than 30K miles) didn't seam to be leaking and the seal to the cover seems solid. Also the pump spins smoothly without any play. Should I break the seal and replace the pump (I ordered one when I thought it was the pump leaking)

3. Here is my proposed install process
a. thin layer of RTV (what style/brand ?) on block and cover, gasket on cover, install cover on block, make sure cover bottom is flush with bottom of block (for oil pan)
b. cover bolts - anti-seize or sealant (what brand / type?), torque bolts to specs
c. NO RTV on pan gasket because the pan gasket is all one piece (see pic).
d. Install pan to torque specs
c. hook everything back up

4. Give it a day and fire it up.

5. Take it all back apart because I forgot something

My comment is in regards to 3C and 4. I have had far better success with RTV sealing properly when left to dry for a day before exposing it to fluids. So perhaps give it 24hrs before you add your fluids back in.

As to which RTV - when you got the store you will see a selection of Permatex sealants. You might need a different tube for the water side vs the oil side. They also make anti-seize.

Permatex The Right Stuff black gasket maker is pretty much all I use at this point. It sets pretty quickly and is pretty easy to lay down.

Regarding item 1 above. I think it’s an alignment dowel used in the factory for assembly. Likely not critical, they are also found in between the block and cylinder heads, and the block and bell housing. The only set that I consider needed is the set in the heads, unless you are using studs for installation.

Thanks for the replies guys. Any thoughts on the breaking the seal on the old WP for a new one (#2)?

Also, I imaging I won't use the bottom corners or curved piece in this Timing cover gasket kit?

Finally finished getting old gaskets and gunk off. I ended up replacing water pump and assembled back to the timing cover and block. I used a thin layer of rtv on the gaskets. I replaced bolts with grade 8s and torqued them to specs with anti-seize. Next I put the oil pan on and torqued that with a little rtv in the corners. Tomorrow I’ll connect the hoses and front dress and get ready to fill up with fluids.

Couldn't find the torque specs for the alt and ps brackets. I just gave them a good old fashioned tightening.

After reconnecting the alternator I posted up a question about grounding the battery.

Thanks. I'll post up after I fire it up.

I've fired it up a few times and the test runs went great. No leaks as of yet and its back too being my daily driver (minus icy or mag chloride days)
Thanks for the guidance.