DD871TI coolant leak

[dar636]

Hello -

My port engine has a coolant leak I am trying to track down. I've a pressure testing kit to pump up the reservoir tank, 10 psi or so and let it sit to see if I can see an external leak.

My question is - if the leak is internal from the heat exchanger to the raw water side, how is this confirmed? Just pull the heat exchanger and leak check it on the bench? The heat exchanger and its gaskets, flanges, etc. are the only place this leak could occur right?

I did have a very small drip that fell onto the main oil filter but it was small enough that I only saw the dried up evidence, not an actual drop. Last trip out I had to add 3/4 of a gallon of mixed coolant to the expansion tank mid trip and I haven't seen the quantity drop since, no coolant in the bilge either.

I hope to see a external leak next time I can pump up the test kit and watch for an hour or so.

 

[rsmith]

The injectors sit in copper wells that provide cooling. It’s a common source of internal leaks. It came seen by pulling the inspection plates and rolling the engine with bar until you can see with a mirror. Unless it’s a 92 with wet liners which you don’t it’s the most likely senecio

 

[Captain Ralph]

Do not exceed 8PSI. I see you are a 71, so it is not a liner seals but the seals under the heads I worry over. DDC used different seals thru the years and some may still distort between the head and block.
This is why I recommend 7PSI closed coolant caps.

There are weep holes on the HE discharge, If these leak coolant, it will be noticed from the outside.
The other side of the HE is sandwiched parts. Coolant can weep out here. Still no way for the coolant to leak into the raw water here.
I have found the inter cooler end covers to leak raw water, not coolant on a TI. TA is a different story.

So, unless there is physical damage (very rare) to the HE core, I don't think your leak is there.

I would consider; When was the last time the cap was opened, Was the HE cool and really full.
The cap should never be opened again. The recovery bottle is where to keep checking levels cold.
You may notice on real cold nights, that recovery bottle gets real low and warm, it fills.
Take this into consideration also when checking coolant levels.

I just serviced my stb main. It's going to take a while but I'll have both bottles at the same level again, soon.
Near empty on these cold nights, 1/3 the way up with block heaters on. 2/3 full when running at temp.

 

[brettportzer]

I believe I had an issue where I had an air bubble or something, where I added coolant a few times, but it didn't appear to be leaking, and then after adding a few times over the course of the summer, it stopped showing up as low and has been fine since then.

Not sure, but that is seemingly what happened.

 

[dar636]

OK, thank you all, good info. I do have the 7 psi caps and will take care to keep the pressure as low as possible when leak checking.

One question - as for leaking injectors, this would show up as water in the oil right? I do not have any trace of water in the crankcase certainly not the amount which was reserviced.

I'll carefully reservice again and get back to the brain trust. I hope to report any easy fix for a change!

 

[Captain Ralph]

OK, thank you all, good info. I do have the 7 psi caps and will take care to keep the pressure as low as possible when leak checking.

One question - as for leaking injectors, this would show up as water in the oil right? I do not have any trace of water in the crankcase certainly not the amount which was reserviced.

I'll carefully reservice again and get back to the brain trust. I hope to report any easy fix for a change!

Water in the engine oil, probably not. air box drain, maybe.
If, If the injector tubes are leaking, the combustion pressure would be bubbling out your fill cap.
Suggestion to look over, the gland connect between the thermostat housing and the coolant riser from the head, both sides.
Also the weep hole between the block and circulation pump.
Leaks here usually follow the contours of the block and not noticed easily.

 

[rsmith]

It cooks off and doesn’t show up in the oil at least mine didn’t

 

[dar636]

Well, it seems I had an air bubble or something... Reserviced the reservoir, leak tested the system at 7 psi, no leak or loss of pressure well beyond the 5 min limit, no visible leaks anywhere though I put some pads down and will keep watch.

I'd like to think I just needed to run them hard enough to bleed out the trapped air. Not sure what else to look for so I'll move along. Thanks all-