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Noticed a wet spot under the truck that isn't snow melting . Not easy to see and harder to photograph, but it appears to be leaking from the coolant crossover pipe gasket on driver side. (135k miles) Mahle sells a gasket kit (#gs33691) and figure I'll replace the thermostat while I'm in there. Seems straightforward enough.
Does anyone have experience with this? Any other items to replace while working in there? Not sure if the upper radiator hose should be replaced if removed- I watched a youtube video claiming it will leak if removed/reinstalled
I have plans to flush my primary cooling system this year, in spring with WARMER weather as we have been colder than usual this winter, and I bought a new thermostat and a Fleece Performance aluminum thermostat housing (not so much for bling but for the fact it's aluminum or won't potentially crack like original factory plastic housing from all the heat cycles but YMMV).
I also bought this sometime ago from SPE, their heater inlet tube fitting kit, since I live in the rust belt and corrosion does happen. I meant to do this when I did the S&S DPK kit but since it took me a liitle longer, I did not want to eff with it. But now that you are having a leak from that crossover pipe at 135k miles, you are having me thinking of pulling the intake off to do the crossover pipe gaskets as preventive maintenance as I am near 150k miles now and then I could that SPE heater inlet kit.
I have not bought these yet, but I am looking into purchasing another turbo coolant feed line as I have read that this are a common failure point on the 6.7s. Looking at an aftermarket option like this one from Swag Performance that uses a braided hose instead of a rigid line. Full Force Diesel sells Sinister Diesel's version. Here's an OEM version.
The other thing to replace would be the oil feed line to the turbo (link for the 15 to 16 6.7) which has a screen on the end of it from the way it looks. IMO, since you are there and it's not that expensive, replace it.
This is just my opinion because I believe by responding to this post, I just talked myself into pulling the intake to replace that crossover pipe's two gaskets and finally do that SPE inlet tube kit. Plus may as well do the turbo oil and coolant feedlines as they are cheap insurance, since I am there. Who knows, maybe I will find out the cause of the leak (thinking coolant myself) on the passenger side at the rear of my engine block. And by no means am I an expert here... good luck.
It seems that only Swag Performance and Sinister Diesel offers the braided hose coolant feed lines for the turbocharger. I'm not 100% sold on them at this point so I may just replace mine with a OEM coolant line.
I have plans to flush my primary cooling system this year, in spring with WARMER weather as we have been colder than usual this winter, and I bought a new thermostat and a Fleece Performance aluminum thermostat housing (not so much for bling but for the fact it's aluminum or won't potentially crack like original factory plastic housing from all the heat cycles but YMMV).
I also bought this sometime ago from SPE, their heater inlet tube fitting kit, since I live in the rust belt and corrosion does happen. I meant to do this when I did the S&S DPK kit but since it took me a liitle longer, I did not want to eff with it. But now that you are having a leak from that crossover pipe at 135k miles, you are having me thinking of pulling the intake off to do the crossover pipe gaskets as preventive maintenance as I am near 150k miles now and then I could that SPE heater inlet kit.
I have not bought these yet, but I am looking into purchasing another turbo coolant feed line as I have read that this are a common failure point on the 6.7s. Looking at an aftermarket option like this one from Swag Performance that uses a braided hose instead of a rigid line. Full Force Diesel sells Sinister Diesel's version. Here's an OEM version.
The other thing to replace would be the oil feed line to the turbo (link for the 15 to 16 6.7) which has a screen on the end of it from the way it looks. IMO, since you are there and it's not that expensive, replace it.
This is just my opinion because I believe by responding to this post, I just talked myself into pulling the intake to replace that crossover pipe's two gaskets and finally do that SPE inlet tube kit. Plus may as well do the turbo oil and coolant feedlines as they are cheap insurance, since I am there. Who knows, maybe I will find out the cause of the leak (thinking coolant myself) on the passenger side at the rear of my engine block. And by no means am I an expert here... good luck.
Thanks for sharing. I haven't got in there to do anything about it yet since it is so dang cold but I'll order parts later this week and hopefully it will warm in the coming weeks. I'd prefer to avoid replacing the turbo coolant line since it looks like a pain and it was revised for MY15/16. Regardless I'll closely inspect for any signs of leakage. Braided line sounds cool, but the common failure point is a seal on the fitting. Appreciate the heads up on the turbo oil line!
Thanks for sharing. I haven't got in there to do anything about it yet since it is so dang cold but I'll order parts later this week and hopefully it will warm in the coming weeks. I'd prefer to avoid replacing the turbo coolant line since it looks like a pain and it was revised for MY15/16. Regardless I'll closely inspect for any signs of leakage. Braided line sounds cool, but the common failure point is a seal on the fitting. Appreciate the heads up on the turbo oil line!
I guess I will see what the coolant line looks like if I do pull the intake to do the crossover pipe gaskets... I'll have those lines, but will double check to see I get the right one... just thinking out loud like I like to do here... I'll have to watch a video on YouTube to see what it looks like to replace the coolant line...
Not going to bother with the coolant line. Inspected with a mirror and it’s in great shape. The 2016’s have a revised line secured with a bolt vs the quick connect/clip on the earlier models.
Not going to bother with the coolant line. Inspected with a mirror and it’s in great shape. The 2016’s have a revised line secured with a bolt vs the quick connect/clip on the earlier models.
old: Old style quick connect Revised
Great information... thank you.
And for FYI, the Flying wrenches dude on YouTube recommended this borescope which will be a future purchase for me.
Listed below..
Last edited by Overkill2; Feb 14, 2026 at 08:44 PM.
Reason: Add to post/delete bad link
Ok, got it done on Saturday. Upper intake manifold is such a pain! But overall, not too bad. Leak honestly could've been from the upper radiator hose with the o-ring so flat but shouldn't have anything to worry about for a while. Also took the time to tighten the vacuum pump bolts. 2 of the 3 accessible from the top were loose. Mahle kit GS33691 includes everything you need including the o-ring for radiator hose to thermostat housing and new thermostat gasket. (I replaced thermostat and housing just cause)
disassembled old vs new replaced thermostat + housing while in there upper radiator hose uses 2 different size o-rings. rts1070 for the lower connection to thermostat housing, and rts1069 for connection to radiator. Loose vacuum pump bolts seem to be a common issue on these trucks. Should be accessible for most by removing the intake pipe. Cleaned ~30k miles ago when installing DPK. Still a considerable amount of soot buildup. Drained and filled coolant almost a year ago and a good amount must remain in the block. Not as yellow as I expected. Celebratory beer after re-installing the upper intake manifold. such a pain!!
Ok, got it done on Saturday. Upper intake manifold is such a pain! But overall, not too bad. Leak honestly could've been from the upper radiator hose with the o-ring so flat but shouldn't have anything to worry about for a while. Also took the time to tighten the vacuum pump bolts. 2 of the 3 accessible from the top were loose. Mahle kit GS33691 includes everything you need including the o-ring for radiator hose to thermostat housing and new thermostat gasket. (I replaced thermostat and housing just cause)
disassembled old vs new replaced thermostat + housing while in there upper radiator hose uses 2 different size o-rings. rts1070 for the lower connection to thermostat housing, and rts1069 for connection to radiator. Loose vacuum pump bolts seem to be a common issue on these trucks. Should be accessible for most by removing the intake pipe. Cleaned ~30k miles ago when installing DPK. Still a considerable amount of soot buildup. Drained and filled coolant almost a year ago and a good amount must remain in the block. Not as yellow as I expected. Celebratory beer after re-installing the upper intake manifold. such a pain!!
Great job. Appreciate the pics and additional information.
Yeah, after laying across the engine bay for some time busting knuckles finessing the upper manifold into place while getting poked by the hood release I was a tad cranky. Should really invest in a top side creeper
Are you intentionally flipping the engine bay the bird??
That's what i got out of it...
Originally Posted by q5 dave
Yeah, after laying across the engine bay for some time busting knuckles finessing the upper manifold into place while getting poked by the hood release I was a tad cranky. Should really invest in a top side creeper
I bought this prior to my S&S DPK install. I love it.
. Not easy to see and harder to photograph, but it appears to be leaking from the coolant crossover pipe gasket on driver side. (135k miles) Mahle sells a gasket kit (#gs33691) and figure I'll replace the thermostat while I'm in there. Seems straightforward enough.
