Freeze Plug on V70 intake manifold blew out

willst5 · Post by **willst5** » 07 Nov 2011, 16:10

The intake manifold freeze plug on my V70 T5 blew out causing a no start condition. I was able to tap it back in with the edge of a steel bar and a hammer. The car is running smoothly again, but I am hesitant to apply much throttle until I figure out why the plug blew out. Does anyone know if it is possible for the turbo to develop excess intake manifold pressure, or is there another potential source of excess pressure in the intake manifold I should check?

Thanks,

Will

1998 V70 T5 170K

FCPEURO · Post by **FCPEURO** » 07 Nov 2011, 17:10

Hey There,

This normally happens when ice builds up in the intake and cause pressure in the intake. Has the car been sitting at all? It sounds like moister got in there and froze, which caused the plug to pop.

willst5 · Post by **willst5** » 07 Nov 2011, 17:25

The plug blew out a few weeks ago when temperatures were well above freezing, but thanks for the info. I was wondering why it was called a freeze plug.

Post by **jimmy57** » 08 Nov 2011, 09:41

It is not a freeze plug. It is a casting plug used for manufacturing access and it also serves as a crankcase vent system vacuum nipple. They blow out due to lean conditions normally as this causes an intake backfire that overpressures and pops it out.
I pry then mack in with a prybar , hose removed, and a socket over the nipple. I first work the edge outward all the way around by tapping a large 1/2 inch drive socket it so the plug flares again. I then use a punch and stake it in in as many places as I can reach. The best way would be to remove manifold and have access to stake it all way around.
On all I have ever had it pop out on they had some fuel delivery issue. Bad check valve causing vapor lock or weak fuel pump, etc. Even faulty MAF.
I had one car pop this out and bend the throttle butterfly. The car was having long cranking and rough running for a few minutes after shut off and restart in hot weather. The owner decided to move off in a hurry before it cleared up completely and it missed a couple of times and popped plug out and distorted throttle blade.

willst5 · Post by **willst5** » 08 Nov 2011, 15:42

Thanks for the clarification. Before the plug blew out, the car started, idled and accelerated normally. The only indication of a problem before the plug blew out a was a check engine code indicating a cylinder misfire about a month earlier. The engine seemed to be operating normally so I cleared the code, and it never returned.

When I tapped the plug back in flush, the car started right up and idled smoothly. I was able to drive several miles around town, but without any hard acceleration or reaching highway speeds. As soon as I did try to accelerate aggressively the plug popped right out. I hadn't staked the plug nor sealed it with a bead of the Loctite 603 yet. Did the fuel delivery problems you've seen usually result in a code, rough idle or poor acceleration?

Post by **jimmy57** » 08 Nov 2011, 15:55

Usually no codes. Long cranking, hesitation, sometimes rough idle. Bad plug wires can do it too.
Anything that can cause an intake backfire or excessive boost pressure could push it out.

willst5 · Post by **willst5** » 08 Nov 2011, 16:39

The last tune up was about 38,000 miles ago and I was hoping to get another 12,000 before doing it again. The car seemed to be running fine until the plug blew out. I'll secure the plug again and be on the look out for any hint of a backfire. It also sounds like it might be a good time to install a boost gauge. Thanks again for the help.

stutteringp0et · Post by **stutteringp0et** » 22 Apr 2013, 22:27

I know this is an old thread, but this is the first one that comes up in a search, so I thought I'd share what I found.

The plug is also discussed in this thread:

https://www.matthewsvolvosite.com/forums ... =1&t=35297

This thread contains a linked PDF that describes the official Volvo method for installing and securing it.

I didn't know about MVS when my plug blew out. I couldn't find it (I was focused on the fuel rail, and didn't look 3 inches to the left to see it) and a couple of my more mechanically friends were on the same page as I was (looking at the fuel rail) - so I took it to the Volvo dealer. $700 later, they explained what it was (but wouldn't point it out to me).

When it happened again last week, it took all of 7 minutes to pop back in, but I noticed that it wasn't staked and had no loctite applied (as is described in the Volvo document linked in the other thread).

So, beware! They want you to come back when it happens again, so they probably won't fix it correctly.

I plan on limping the car around for a while until I have time to remove the intake manifold and repair it correctly (something that $700 should have paid for)

Post by **cn90** » 23 Apr 2013, 09:50

I am wondering if anyone has a photo of this culprit?

Post by **jblackburn** » 23 Apr 2013, 10:59

cn90 wrote:I am wondering if anyone has a photo of this culprit?

Right where that vacuum line attaches.