Background:
88 Gt with 2008 Lacrosse L26 bottom end & L67 top swap.
I thought I had a bad water pump, but it turns out that it blew the rubber expansion plug out of the back of the water pump.
You can see the location below - ( location #1)
Ignore all the other crap in the picture as it was taken VERY early in the build process. Heck, it's not even the same engine.


Now I KNOW that I put that plug in there really tight. I'm pretty sure I even used the impact gun on it.
But it was particularly hot the day it blew (first week of September) and I was driving it a bit hard because I had to get home. My daughter had to be at school for Marching band (football game) and I was running late.
Plus it was Friday and I was ready to put distance between myself and work, if you know what I mean.
I was sitting in traffic for a while before I noticed the steam. I also noticed that the radiator fan was not on. So it probably was overheating. I could never get the temp guage working right. These are all problems to hopefully solve this weekend too.

But what I want to know is if anyone else has had problems with these rubber plugs coming loose on their 3800 swaps.
What other solutions might I look into rather than a rubber plug.

Have not had that problem on mine.

Holy...! I wouldn't trust a rubber plug there so inaccessible. I heard people threading the LIM. Can that be done there too?

I have only used a rubber plug on one swap and there has been no issues with it. I did make sure it was seated 100% when I tightened it down. I have used freeze plugs on other swaps. I am sure it running hot caused the plig to come out. Pressure built, rubber got soft and out it came....

I fired one driving around the university campus back in '09. I just happened to be rolling past a girl on the sidewalk, who jumped about 20 feet when the plug ejected - sounded like a gunshot. The reason it came out was because the water pump began to weep, and the engine temperature was rising while I was trying to get back to the parking lot, so pressure built until the plug ejected.

Using a rubber expansion plug is a "rigged" solution, they should only be used on a temporary or emergency basis. I learned not to be as poor/cheap as Darkhorizon (who offered up using that plug for the coolant return on the later year cars), which has served me well. Get a permanent freeze plug installed. Watch your temperatures.

Tap the hole w a 3/4 NPT tap and screw in a pipe plug with J B weld on the threads. Done!

quote Originally posted by Dennis LaGrua: Tap the hole w a 3/4 NPT tap and screw in a pipe plug with J B weld on the threads. Done!

Working great for me.

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Project Genisis Lo Budget 3800SC swap in progress

88 formula 3.4L 4t60 swap

quote Originally posted by Dennis LaGrua: Tap the hole w a 3/4 NPT tap and screw in a pipe plug with J B weld on the threads. Done!

Thats what I did. But why use JB weld? I only used thread sealant...

Thanks for the suggestions. I'll try the NPT threads eventually. But for now I put another plug in it. Since I don't have to replace the water pump today, no need to pull the cradle.
I still plan on pulling the cradle in the next few weeks to redo the AC system and weld in a new battery tray. I'll tap threads into the water pump at the same time.

I also found out that my radiator fan was dead. I swapped in another one from my other Fiero and it turns on at 187 and shuts off at 177 according to the laptop plugged into the OBDII port.
All that's left to fix today is the temp guage in the dash.

I'll add some pictures and stuff when I get the NPT plug in there.

[This message has been edited by 2002z28ssconv (edited 11-05-2011).]

quote Originally posted by ALJR: Thats what I did. But why use JB weld? I only used thread sealant...

A year ago, I tapped the LIM hole and Water pump hole and screwed my fittings in with sealant. They both leaked. I searched pennocks and found some quy say to tap the holes and seal with JB weld. A year later still holding. It am not sure why the sealant did not work - I think maybe because the heat, pressure and coarse threads.... Anyone else have other solutions that work well?

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87 Formula Clone, 3800SC, 3.4 pulley, 4T65E-HD, HP Tuners, 12.98 at 103.4 1/4 mile, Regal GS Gauge Cluster.

Never had one fail on me in the 4+ years I have been using them.

9/10 times I have sanded out the hole with some sandpaper on the end of a drill to get the crud out, as well as try to make the hole not as tapered.

i used a plug on my 3.8 sc . i worried that it might relax the rubber over time . not enough to loose it's seal but it's friction to hold it in place. i used a dremal cut off tool in my drill and made 2 slight grooves on the inside of the bore before inserting the plug . this way it would tend to have rubber squeezed up in those grooves and have a lot of friction.

3/4 fitting on timeing cover hole and LIM filled with JB weld could have used same fitting as timeing cover

quote Originally posted by ALJR: Thats what I did. But why use JB weld? I only used thread sealant...

The water pump return hole diam is a bit too large for a 3/4 NPT tap and plug to get a tight seal with just thread sealant. JB Weld will not only seal it but insure that the plug is cemented in and will not come loose. Going on three years and the plug on my install hasn't moved or leaked.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

3/4" NPT plug... Installed with JB Weld... Working great... thanks for the recommendation.