Plenum Gasket Leak = Engine Damage?

[allmotor]

Is it common for older V6 pathfinders to have a slight coolant leak from the intake manifold's gasket (under the plenum)? If so, would this cause severe engine damage even if I made sure the coolant were always filled to the top? (I'm asking because some mechanic told me that it would damage the engine if i didn't take care of it now.

Edited August 31, 2008 by allmotor

[Slick]

leaking from the INTAKE plenum? not good...... no, intakes aren't supposed to leak.

[Chriskaw440]

Typically ANY kind of coolant leak is not good....especially when it comes to the engine gaskets such as intake manifold or head gaskets. Coolant and oil are not friends when they are forced to share the same space at the same time lol.

 

is it actually the intake manifold gasket leaking?? or are you just seeing coolant ontop of the engine coming from somewhere under the plenum? because on the underside of the plenum there are a few coolant hoses (rubber) that may be cracked/dryrotted. If thats the case, pretty non invasive repair. If it is the intake manifold gaskets, then its a little bit more of a task but its not rocket science.

 

 

 

Fortunatly if you are a somewhat experienced mechanic, it's not that hard of a job to replace the gaskets in your own garage, just takes some patience (lots and lots of things to move out of the way or disconnect)....and the gaskets themselves are pretty much dirt cheap.

 

If you HAVE to have a shop do the repair(s) you may be looking at close to a grand in cost due to the cost of labor + parts and miscellaneous parts that may need to be replaced once the plenum and manifold are removed. There are LOTS of hoses under the plenum and its always a good idea to go ahead and replace them while its apart due to age of the vehicle. The rubber seats for the injectors should always be replaced too (if it is MPFI) even if they look ok.

 

The ONLY real pain in the ass thing I ran into when I did my knock sensor replacement, were the two coolant lines at the very back of the plenum that have to be reconnected. If the hoses are the pre-formed type, good luck finding any from Nissan....I had to fabricate my own when necessary or just use longer lengths to avoid them getting kinked up from having to bend much to fit.

 

It's also a good idea to replace the valve cover gaskets at the same time, since they too are inexpensive and the drivers side valve cover is not accessable otherwise since it sits under the plenum (again, this is if its MPFI set up like my 1990 SE is)

 

always always always mark everything as to where it goes, especially the distributor.

 

Of course these are just suggestions for if you decide to do the work yourself.

[Indigent]

There are no coolant channels that go throught the plenum and down to the manifold. All of the coolant that runs through the plenum comes from the two small hoses at the back of the engine. If you have coolant on that intake gasket, it is more than likely coming from somewhere up above.

 

Do you have the ability to take a picture of this coolant leak? That would be incredibly helpful.

 

indigent.

[allmotor]

There are no coolant channels that go throught the plenum and down to the manifold. All of the coolant that runs through the plenum comes from the two small hoses at the back of the engine. If you have coolant on that intake gasket, it is more than likely coming from somewhere up above.

 

Do you have the ability to take a picture of this coolant leak? That would be incredibly helpful.

 

indigent.

 

 

Yeah, I'll take a picture and post it soon, btw my pathfinder is a 98 and the "leak" is so minor that I havent had to fill the resivor (ever) and the only sign of the leak is some dried up coolant underneath the (plenum between the manifolds) . additionally, I have never had any Overheating issues in the past with my truck! I'm just wondering if this mechanic is just trying to freak me out into getting the work done with him asap ($500 labor to replace a gasket?) because suposedly he saw this before and it could "severely damage my engine". Should I really be worried or should I just monitor it?

Edited September 1, 2008 by allmotor

[Chriskaw440]

why that sneaky little mechanic...I bet HE dumped a little cup full of antifreeze there and then said "see that, you have a coolant leak!" lol hopefully that would not be the case of course.

 

Since its a '98 (still pretty new in my book!) my guess would lean more towards one of the small hoses under or around the plenum rather than an engine/intake manifold gasket.

[GrimGreg]

Yeah, if you have never seen any sign of leakage or ever had to add coolent, then you probably have no issue. It would take a good bit of coolent leaking to cause any issue.

[Huck]

Since its a '98 (still pretty new in my book!) my guess would lean more towards one of the small hoses under or around the plenum rather than an engine/intake manifold gasket.

My 92 has those little heater hoses routed under the plenum. I had a leak there a while back. It created quite the problem for the cooling system. When I drove back and forth to work, it had no problem. When I tried working her really hard (hill climbing especially) the system would overheat. My mechanic told me that if the system isn't completely closed and air can get sucked in (specifically those hoses) when the engine cools down, it can make the system boil over. And a boil over can warp heads and crack blocks, etc etc.

Edited November 24, 2008 by Huck

[arcano]

My '98 developed a leak from the hoses under the plenum which looked exactly like what you are describing. I was so positive it was an engine gasket I took the truck straight to the dealer, expecting major repairs. It turned out to be two separate - and relatively small leaks from two separate small hoses feeding the intake. I went ahead and told the delaer to replace them all while he was in there.

 

The bill was still around $400 due to the number of small hoses to replace and the amount of work involved to get there. Still, I thought it was very reasonable for a dealer.

 

By the way, this repair also fixed a misterious coolant loss that had been bothering me for months, and now the truck looses absolutely no coolant.

 

Good luck!