Mike S

Well, I stumbled upon an excellent opportunity and drove down to LA on saturday to pick up my new ride. She's a 1987 951 with 135,000 actual miles on it. The odometer reads 105,000...but carfax showed that to be incorrect and the previous owner/documentation showed the mileage to be around 30k higher. Great interior condition, a few cracks on the dash but otherwise perfect, new clutch, new front oil seals, new timing belts, new water pump. The paint is the worst part. It was repainted by an average painter. Not maaco...but not a 4k job either. It has some orange peel and just overall average finish. Its new paint so it looks great from 10ft away...but i'm picky about paint..so up close its less than perfect. The price for all this fun.....7k. Can't beat that.

So, that leaves me with a couple of questions.

1)Compression was a solid 130 on all 4 with zero variance, however I've now noticed some air in the cooling system(temp needle jumps around). I'm going to bleed it again...but if it keeps coming back am I safe to assume that I have a head gasket on the way out?

2)I have an autothority chip of some sort on it with a cone filter on it. It makes a ton of power, but i've noticed that around 85-90mph, 5th gear under full boost i'm getting a shutdown of sorts. Theres a rough surge then, the boost drops off and it won't accelerate. From what I've read this is an overboost cutoff...however I can hit 2 bar of boost again without restarting the car...is this still the same condition?

3)The previous owner unbolted the return tube near the cat.....so when you let off the gas under full boost you hear the "whoosh, whoosh, whoosh" of boost dumping out. Is this harmfull? Would this cause my problem from #2?

thanks,
mike

guardsred951S

Not sure with #1....

2. Do you have a stock wastegate? If so, it sounds like it's a little weak in the spring and is dumping early a wastegate upgrade or shimming would fix this. You're not hearing any knocking are you - the knock sensor shuts everything down it boost is too high and you get pre-ignition. With APE Stage II, a jetted banjo bolt is used to get a boost spike to about 14.5 PSI or so. If you have their MAF kit (Cone filter behind the left headlight), then boost will be more smooth.

3. No harm in leaving the wastegate pipe undone from the rest of the exhaust. A couple of guys leave it open. It makes things a little loud but
no big deal - I don't think it would have anything to do with #2. It just is being vented to atmosphere instead of the exhaust.

HTH

<img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" />

RPG951S

1) It can be very difficult to properly bleed the coolant system. I like to jack up the front end ALOT while bleeding...

2) Sounds like a typical non-stock overboost situation. I don't think chipped cars go into the 'overboost-limp' mode that stock cars would...

3) If I rememeber correctly, according to Corky Bell's book, smoothly merging an external wastegate exhaust into the main exhaust is actually preferrable to venting it to atmosphere.

Mike S

Thanks for the quick reply. No I'm not hearing any detonation, however it certainly seems like a shutdown is occuring. It's a pretty violent surge/bucking going on..boost drops off to 0, then limits itself to around 1 bar for a minute or so. As far as I can tell its the stock wastegate. I do beleive that I have the APE Stage II kit though. Its a pretty smooth curve of boost that hits hard around 3,800rpm. The cone filter has been slightly rerouted and it pops out in front of my front tire(facing the tire actually). Nice cold air setup...but I wouldn't want to drive in the rain with that cone there. I may have to put it back in the engine bay.

Dal Heger

Ok, first of all, aftermarket chips do go into overboost protection mode. Most likely you have a problem with the boost control system. The most common is the rubber line that goes from the cycling valve (tan round thing under the intake manifold, between the 3 and 4 intake pipes) to the wastegate. The air signal to open the wastegate isn't getting to the wastegate (which remains closed) and overboosts. This causes the KLR to tell the DME to go into limp mode (yes, even with aftermarket chips). Replace that line or the line that goes from the turbo to intercooler pipe (banjo bolt) to the CV.

1) it is not that difficult to purge the cooling system. open the banjo bolt at the top of the engine and pour coolant into the reservoir until coolant start pouring out of the banjo bolt. Close the bolt. With the rad cap off, start the car, put the heater on full heat and the fan on full. This will also purge the heater core. Let it warm up (rad cap still off). rev it a few times to make sure that you dislodge any remaining air pockets, it may "burp" a few times, no worries. As soon as it gets warm and no longer burps, put the rad cap on and you're done.
The best way to test for a failing head gasket is to do a compression test, or grab a cooling system pressure tester and pressurize the cooling system. see if the system hold pressure. If it doesn't then look for where the coolant is going. Take out the spark plugs and use a long q-tip swab to see if there is any coolant leaking into the cylinders.

3) if you're hearing the woosh when you let off, it's not from the exhaust (wastegate). The wastegate will be fully closed when you let off the throttle. The woosh you hear is most likely from the blow off (or recirculation) valve. It's the little round plastic thing next to the coolant overflow tank. to test this for proper operation, take it out and try to blow through any of the holes. if you can blow through ANY of the holes it's toast, get a new one. The function of this part is to let the pressurized air back into the intake of the turbo when you let off the throttle. It keeps the turbo spinning when you let off, and prevents turbo damage due to the suddenly closed throttle backing up the column of air to the compressor blades, quickly and drastically slowing them down.

Hope this helps.

Dal.

Mike S

Hmmm....lots of good advice there. The whooshing sound I'm getting is definitely coming from the wastegate pipe near the catalytic converter and only when I let off the throttle under boost. I'll take a look at the blowoff/recirculation valve. I was looking at it last night and noticed that the bottom of it(largest diameter opening) wasn't hooked up to anything. I'm assuming that he was just dumping it into the air...but I'm trying to see what it should be hooked to.

Russ Murphy

Welcome to the party.
To #1: Yes. Also, 130 psi is a little on the low side. 140-155 is more typical of one of these motors with decent ring sealing.
To #2: Do you have the stock AFM with a cone filter postioned in the center of the engine bay or do you have a MAF conversion with the cone filter located behind the left headlight?

Mike S

Yeah, I was thinking 130 might be a tad low...which is what led me to think that air bubbles continually appearing the coolant was a sign of a head gasket that was sealing well.

I'm not familiar with the turbo parts yet...maybe I can snap some pics tonight. It looks to me like a stock AFM setup with a cone filter on the end. The cone filter was relocated to the driver side fender well and the cone sticks into the wheel well itself in front of the tire.

Mike S

Oh man! Some days you win and some days, well.....you should never get out of bed. So I get back from work, start her up for a quick drive to the store and she idles a bit rough. She warms up and halfway down the block under about 1 bar of boost.....she stumbles badly...i look in the rear view mirror and there's nothing but white smoke everywhere. Not good! :-( Just not good. So...it looks like I'll be doing a head gasket R&R. So pissed! I had perma grin for the last 3 days...then this! It looks like the overboost situation must have caused my problem.

blu951

Aw man,
Sad to hear that. Hope things turn out better when the car is running again.

dmoffitt

1) get an aftermarket boost gauge.
2) if you're dumping the DV into the air, perhaps this is why you're stumbling/bucking - improper metering of air/fuel (thinking air's there, that's not, cuz the air is metered pre-turbo).

good luck w/ the HG, it's not that bad of a job to DIY - replace all of the vac. lines while you're in there - and check the coolant hoses, while stuff's out. i went all out when i burnt a valve and sent the head off for some work, but I think you can limit your replacemets to $150 widefire headgasket kit(www.lindseyracing.com) - includes intake and exhaust gaskets, the hg, and other top-end gaskets/seals, and about 150-250 in vac. + coolant lines (talk to ian: <a href="http://www.944online.com)" target="_blank">www.944online.com)</a> and perhaps some silicone lines to replace the hard plastic vac. hoses while you're at it. might as well eliminate the source of vac. problems while you're at it.

also i suggest a stratmosphere DV or similar(http://www.stratmosphere.com/hyperboost.htm) - and re-pipe it properly instead of to the atmosphere.

best of luck!!

cruise98

Mike S:

Please post a picture of that intake setup. I have never seen the stock airbox turned around and pointed towards the fender. But there is always a first. The stock j-shaped rubber tube would have all of the connections pointing down, and they would interfere with the alternator. Inquiring minds want to know how this was done. You might have a mass flow sensor.

If the recirculation valve is not connected at the big end, you will have a HUGE unfiltered air leak! This would be very bad. The turbo compressor wheel needs filtered air, or it can easily be destroyed. For maximum power and engine longevity you need to eliminate all of the air leaks in the intake system and now is the opportunity to do so as others have suggested.

If you are getting unmetered air into the system, the engine is running lean and this can/will cause a head gasket failure among other things.

Welcome to the boostaholics club! Get it running right and have fun with it.

Mike S

I'll post some pics tonight, but apparently I didn't do a good job of describing it. The stock airbox has been removed and replaced by straight tubing with a conical air filter on the end of it. Instead of leaving the cone air filter pointing towards the back end of the driver headlight the PO rerouted it to the drivers fender well. I will post some pics though because I can't identify some stuff and one of the connections I can't identify is open.

Danno

I think the stock rubber J-pipe must be flipped 180-degrees as well. That would explain some of the hoses & connections not lining up. I'll bring one of my new headgaskets up for you to check out...