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951 DI Engine Leak Test

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tkarvelis

tkarvelis

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I have made it this far!!!

I am in the process of completing the leak down test on my DI.

I have read the service manual, and I can not wrap my head around the procedure. It appears the procedure is written around the engine being inside the ski, and still connected to everything. My engine is out and pulled apart.

I don't understand why you would remove the rave valves. I would think you would want to test this components installed.

So does anyone have a good procedure for this?
 
I follow the manual, I never pressure test with the raves in. I have never pressure tested a DI, but it's gotta be the same or close to a carbed engine
 
Thanks [MENTION=57920]racerxxx[/MENTION]. Is there a reason not to pressure test the engine with the raves in it? Will the not survive the pressure, or will they leak by?
 
I have left the raves in, caps in the throttle body boots. block off on the exhaust manifold. I also put temporary rope sealant on the temp & map sensors in the boots. they leak a bit. Can't think of anything else off the top of my head. make sure you check the water jacket separately. when testing the case, I put soap bubbles over the water jacket nipples in the event pressure escapes into the cooling side.
 
Sounds good. When I get time after the 4th, I will be testing her. Taking the GTS south for the 4th. Wish I had the GTX DI running, but life and kids require more attention...
 
Not sure how carried away your getting with your rebuild, but through trial and error I found a perfect match on the engine color. If you have a PPG dealer in your area, there are two single stage (omni) paints mixed about 50/50 that are near spot on. I can get you the paint codes if you want them.

Also, PVC 1.5" drain pipe caps work perfect for plugging the throttle body boots. Make sure the clamps are fairly tight though. 5 psi can send one across your shop & scare the poop out of you! :D after that I stuck them in the lathe & cut ridges in them to fit the raised rib in the boot & it didn't happen again. Not a big deal, just worth mentioning. The temp & MAP sensors I usually put a little rope caulk on the seal them up during the test too. Install the rail, etc. I might have pictures of this too.



The common leak I found was the head gasket on the water jacket side. Oddly I had one leak between the gasket halves. After that I drill out the rivets to separate the halves & give them a coat of copper spray. Works great!
 
I had no luck using the intake caps in the factory test kit it leaked around the intakes where the sensors pop in, so I made aluminum block off plates for the intakes and it tested perfect !
 
wfo speedracer said:
I had no luck using the intake caps in the factory test kit it leaked around the intakes where the sensors pop in, so I made aluminum block off plates for the intakes and it tested perfect !
Click to expand...

I like having the reeds & boots installed so they can be leak tested too. I agree on the sensors, they leak bad & fast under pressure. I uses a strip of this around/under each sensor. Seals 100% & is easily removed after the test. IMO its easier than installing plates & then installing the boots after. just my opinion of coarse. :)

I have this stuff in my shop for other things too, so that helps.....

mmm08578-1.jpg
 
213.jpg


My plugs for the throttle body... 1 1/2" pvc caps with a grove cut into them with my wood lathe...
 
[MENTION=57696]68ragtop[/MENTION] -
Do you think using RTV will seal the sensors? I tried a sealant I have used to seal RF Coaxial connections, and it does not stick enough.

I am debating on the RTV incase I need to replace the sensors at some point, but I dont want to loose that much air either.

I am having fun leak testing this engine... The sensors leak, the head leaks, and I not know what else...

I have 1211 on the head gasket, so I am shocked it leaked. I did not put anything on the base gasket, but I guess from reading I should have.

Time to order more stuff...
 
I used 3m strip caulk to temporarily seal the sensors in the boots. just put a thin bead in the groves on the sensors & poped them in. I removed it when I was finished. I found the head gaskets sealing the water jacket problematic. I had one brand new oem gasket leak between the two halves of the gasket. After that, I started drilling out the rivets on the new gaskets & giving all sides a light coat of copper spray. works great. I haven't had a a new base gasket leak yet, but in one of my mockups when I welded a case & was leak checking, I spray a used base gasket with copper & it help perfectly. also found it useful to seal off the water jacket side & put a gage in that at the same time. Easier to check both halves, & if one side leak int the other you will see the pressure increase in the presureless side.

3m8578.jpg

I had the strip caulk in the shop, only reason I used it, but it works great. Nice job on the pvc plugs. that groove you cut makes all the difference in the world too.
 
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[MENTION=57696]68ragtop[/MENTION] - Well pulling the sensors, and sealing from the inside worked. I was able to hold 5 lbs for 21+ minutes. I lost a 1/2 pound in those 21 minutes... The water jacket... that is another issue. I will need to get another head gasket unless you think I can reuse it, but it has 1211 on it, so don't know if it has silicon contamination. I have copper sealant, but i screwed up, and used 1211 instead...

[MENTION=57920]racerxxx[/MENTION] A week or so... Maybe longer.
 
If its an oem gasket it can be re-used if the black coating isn't peeling off. But coat all sides with copper spray & separate the halves. Sealing the combustion chamber is easy, its the water jacket thats a SOB.

if there are any dings, or other damage to the edge of the head or edge of the cylinder head, it'll leak without spray sealant, & if its bad enough that won't work either. I never liked how the jacket seals. Everything has to be just perfect & straight for it to work. Not a problem on the assembly line at BRP, but not so easy 15 years later as these parts age & are not perfect anymore.
 
I found out the black stuff comes off with brake cleaner... I guess another head gasket in in my future. Hopefully Nick has one in stock.
 
Maybe take the gasket apart, clean all the black sealant off & copper spray all 4 sides. Its the rib in the gasket that makes the seal anyway. I have removed copper spray with mild solvent that didn't hurt the oem coating, but brake cleaner is pretty nasty. I suppose the 1211 didn't want to come off otherwise. I'll bet it works fine.
 
I have one on order...

But something is bugging me. When I leak tested the top / bottom half (air pressure through the exhaust, I left the vent for the counter balance gears open, and the small tube on the bottom of the crankcase open. It still passed with great number (lost 0.5 lb. over 21 minutes). It does not make sense unless that small nipple close to the PTO has a check valve on it.

Hmm Time to dig into it deeper
 
tkarvelis said:
I have one on order...

But something is bugging me. When I leak tested the top / bottom half (air pressure through the exhaust, I left the vent for the counter balance gears open, and the small tube on the bottom of the crankcase open. It still passed with great number (lost 0.5 lb. over 21 minutes). It does not make sense unless that small nipple close to the PTO has a check valve on it.

Hmm Time to dig into it deeper
Click to expand...

The vent is the only thing exposed on the CB side (as I am sure you know) I put a small gage on that nipple to see if pressure rises at all during case pressure tests. Really shouldn't leak because those CB seals works pretty well in my experiences. On the second part are you talking about the air pump oil return line? unless the case has a leak at the parting line, there's no way for pressure to get in there. it would have to get into the CB cavity, then past the double seal into the air pump cavity. seems doubtful you need to worry about that. If that's what your talking about. This sounds crazy, but the cases really should hold pressure for days, not that that is necessary, but if the pressure is falling, I'll bet you can find it.

The DI case I welded up was a horror to seal up (welding wise) I won't try that ever again & I am a pretty good aluminum welder. When I finally got all the pinholes welded up, I thought the engine together with no pistons & old gaskets. That thing held pressure seemingly forever. I laughed because it was a sloppy, non clean test assembly. So, then a guy takes all the time in the world & gets a leak. go figure. ;) But, like you mentioned, as long as its a really slow leak, it will be just fine.
 
Grr...

I sprayed the copper coat on all four sides of the gasket. Assembled it, and it still leaks... same place, opposite side of the head from the water exhaust.

Before I assembled it, I laid the head on a piece of granite, and used 1000 grit paper to confirm flatness. The head had a uniform sheen to it..

I wonder if I have to let the copper spray dry overnight???
 
No need, that stuff sets up pretty quick. The good news is if you take it apart the copper will clean up with a very mild solvent. Can you post a pict of where its leaking. I'm not sure from what your describing.
 
Right around the two bolts near the rave nipples. I hope the jugs are not warped... it will be the end of my season... I guess I could get them decked, and goo with a thicker base gasket...

314.jpg
 
I took the head off last night, and I reapplied copper spray. This time I went a little thicker, and let it site overnight. Still no luck.

It leaks down from 5 psi to 0 in a little over a minute.

I am stumped. I thought that it could be the head, but after doing a fine sanding on a piece of granite, I dont think it is.

This is the second gasket. The first was a WSM, the second was OEM.

The first gasket I applied 3bond 1211 on it.

Looks like I will not be painting this weekend....
 
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