bulldogg Posted November 30, 2010 Share Posted November 30, 2010 I have a 1981 285 maxidyne engine that I need help with. I am looking for the rubber cover/gasket that connects from the intercooler to the intercooler filter Box. Its a rubber cover, Mines dry rotted and is preventing the turbo from boosting. I tryed mack and they dont have this. Any leads on a junk yard or?? Its off a 686 CF mack. Thanks Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted November 30, 2010 Share Posted November 30, 2010 yea I heard they were NLA from mack. did you try PAI? . They make alot of mack knock off parts? I may have a used spare at the yard will have to get back to you on this over the weekend Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 6, 2010 Author Share Posted December 6, 2010 what i need Quote Link to comment Share on other sites More sharing options...
oldmacktrucks Posted December 6, 2010 Share Posted December 6, 2010 From the looks of your picture the gasket your talking about appears to be an exhaust gasket / duct to exhaust the air being pushed thru the intercooler fins from the tip turbine out of the engine compartment (should have nothing to due with lack of manifold pressure) I've added 2 pictures, one of what my 285 intercooler looks like, and a picture from my Mack service manual showing you how the air is directed thru the box. The air being supplied to the tip turbine is on the other side of the engine, from the looks of your picture the gasket your talking about apears to be on the drivers side? Its hard to tell from what you posted. If I'm correct and you still have no boost, your intercooler may be leaking or you might have a bad turbo. Keep us updated -Sean Quote Link to comment Share on other sites More sharing options...
Rob Posted December 6, 2010 Share Posted December 6, 2010 what i needI know how half assed this sounds but you can make that gasket/seal from neoprene rubber sheet and automotive vinyl top contact adhesive to glue the lapped ends together. For extra strength you could order a small sheet of neoprene impregnated cloth for the same purpose and it will be much stonger.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
Lmackattack Posted December 7, 2010 Share Posted December 7, 2010 Yea I have never seen that one before. The gasket I thought you needed was the one that goes under the box cover between the charge cooler and box top. the "gasket" you show (as mentioned) looks like it just routes the air that passed thry the cooler to a diffrent aera. Also noted that this air is not boost. its just air that the turbine pushed thru the cooler to cool the boosted air. Where does this gasket route air to? trans cooler,oil cooler??? your truck should make between 23-25PSi of boost under load. less than 23 you have a leak or tired turbo / engine etc...., if you hitting 25+ you got a strong runner. mine pushes 27-30 PSI on cold days and can keep up with a 300-350 mack Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 7, 2010 Author Share Posted December 7, 2010 ok found out the truck is boosting, but does not make the normal sound a 285 is known for. When it boosts theres a large air leaking sound coming from this cover. Is that the cooling air?? It doesent make the siren type sound the 285 normally makes when boosting and slowing down. Would this leak prevent that sound?? Ive found a place called Rubber world in my area thats making a replacement for me. Thanks for all help ken Quote Link to comment Share on other sites More sharing options...
oldmacktrucks Posted December 7, 2010 Share Posted December 7, 2010 That gasket should have nothing to due with it, it looks like its there to exhaust the air out of the engine compartment. All trucks sound different, as long as its boosten' I wouldnt worry about it Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted December 7, 2010 Share Posted December 7, 2010 the sound you hear from tip turbines is coming out of the cooler fins. That gasket is catching the air and sound and routing it to a diffrent aera where you cant hear it as good. If we had a pic of where its routing the air we may have a clue why they re routed it. if it was routed to a componet that needs cooling its likely that the air you hear leaking out is from your torn gasket. This is because it can escape thru the tear faster than where it was intended to be routed thry. again a pic of it would help us better...just as a learning experince take a better look at how the air flows. you will see that just a little boost is bleed off (1" pipe fom the box to the turbine) and used to power the turbine, then IIRC that air that powers the turbine is let out into the engine compartment. the turbine then pulls air from the filter thru the top air filter tube, thry the turbine and pushed across the charge cooler fins, it exhausts out into the engine compartment. 95% of the boost from the turbo runs into the top charge cooler, thry it, than out the bottom and into the intake manafold. Its a weird setup but simple to see how it works in an exploded view.you may also want to look at the Check Valve (located on the 1" pipe)(unless it was not needed for your applacation?)between the box and turbine. it should have a rubber "flap" in it that only allows air to flow into the trubine. if air tries to back flow into the engine it should shut.this prevents unfiltered air to enter the engine when the turbine is at idle. this valave will have a metal tab helps controls how much of the boosted air can flow into the turbine. if its missing or bent so that it lets to much air in you can over speed the turbine and louse boost, its a simple check.hope this helps..Trent Quote Link to comment Share on other sites More sharing options...
b61mack Posted December 7, 2010 Share Posted December 7, 2010 I have a 1981 285 maxidyne engine that I need help with. I am looking for the rubber cover/gasket that connects from the intercooler to the intercooler filter Box. Its a rubber cover, Mines dry rotted and is preventing the turbo from boosting. I tryed mack and they dont have this. Any leads on a junk yard or?? Its off a 686 CF mack. ThanksSince it is a firetruck i would say it deflects the hot air off of the under side of the cab. i drove an F model with 300+ and the shifttower would get pretty warm from the tipturbine blowing on it. if you are not driving it alot you might leave it off. you might take the hose off the tipturbine and reach in there and see if you can turn it by hand i have seen them froze up from sitting. Ron Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 8, 2010 Author Share Posted December 8, 2010 [ will post more pics today. Im not understanding how to get into the turbine to try to move it? The truckwas sitting almost 4 years without being run hard. I just figured the torn cover was the problem, From what I can tell there is a filter on the inside of drivers side where my first pic was taken I was told its the intercooler filter. But maby I was told wrong. Thanks again, also when driving the truck, The pyrometer reads very warm when under a load. it exceeds the normal temp. 1300 degrees. I always let off before it reaches that high temp. ken Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted December 8, 2010 Share Posted December 8, 2010 yea 1300* is to high. the tip turbine is held on with a lage V clamp and the bleed tube hose clamp. remove those 2 clamps to get the turbine off, and see if that turbine wheel spins freely. Quote Link to comment Share on other sites More sharing options...
b61mack Posted December 8, 2010 Share Posted December 8, 2010 what i needYou need to be on the other side,there is a 6" hose that connects to the aircleaner. Ron Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 9, 2010 Author Share Posted December 9, 2010 Ok the pics as follows, Turbo on pass side of truck, looks like turbine fan on drivers side where the gaskets bad. Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 9, 2010 Author Share Posted December 9, 2010 d-side Quote Link to comment Share on other sites More sharing options...
oldmacktrucks Posted December 9, 2010 Share Posted December 9, 2010 The two black hoses are the intake hoses from the air cleaner. One goes to the turbo (engine intake) one goes to the tip turbine. The gasket you posted the pics of before does nothing more then deflect hot air out of the engine compartment, it serves no real purpose and honestly you really dont need it, and it shouldnt matter at all that it has a rip in it. If you have high exhaust temps your tip turbine could be seized, the tip turbine air cleaner might be clogged or the fins on the intercooler might be clogged. I would start simple, change your air cleaners! It say right on the air cleaner box that if high exhaust temps occur change the filters Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 9, 2010 Author Share Posted December 9, 2010 I changed the filters already, Soo I will try to free the fan on turbine. With the truck sitting for years I guess this hopefully is the problem. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted December 9, 2010 Share Posted December 9, 2010 just a fyi you can remove the black pipe to/from the air filter/tip turbine and see the wheel. Check to see if it spinns without removing the turbine. Its a sealed unit and has self contained oil. Start the truck up and watch the wheel. it mostlikely will not spin at idel RPM but if you bring the revs up to around 1500 and get 1-2PSI of boost it should start to move on its own. If you can rev the engine and the wheel does not spin thats a problem. Im still wondering where that gasket goes to. If it has a rats nest in it the air will not be able to get out after it passes they the charge cooler. I say check the flow and movement of the turbine and then start looking for any blockage or restriction to the charge cooling system. also I know you said you have good boost but I did not see what it was exactly. if its less than 18-20 psi it may be overfueling with low boost and thats another way EGTs can get high. I had a bad turbo with mine and was only getting 14 psi max. I was hitting 1200* by the time I made it to 5th gear and had to feather the throttle and watch the gauges with a load on. Quote Link to comment Share on other sites More sharing options...
bulldogg Posted December 12, 2010 Author Share Posted December 12, 2010 Well after hours of trying to figure out this problem, Found out the Clamp holding the turbo togather was missing. Made new clamp from two older clamps, It stopped the air leak and The truck FLYS now. Runs like a rocket. Thanks again for all replys. 1 Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted December 12, 2010 Share Posted December 12, 2010 the clamp that holds the turbo snale to the center section? or the outlet of the turbo to the crossover pipe to the box? that would explain your high EGT and the tip turbine not working or sounding as it should... glad you found the issue!. Quote Link to comment Share on other sites More sharing options...
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