cruiseliner64 Posted Friday at 10:49 PM Share Posted Friday at 10:49 PM Hi all,We started the Cruiseliner for the first time in 7 months today and it started first turn of the key....but it wont build air pressure over 20psi.When the engine is shut down the air can be heard leaking back through the compressor.Im thinking its the unloader valves are stuck.My question is does the compressor head have to be taken off to clean them or is there some other way to clean them? I think its a Midland compressor.Thanks Paul Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/ Share on other sites More sharing options...
Joey Mack Posted Friday at 11:01 PM Share Posted Friday at 11:01 PM (edited) Is the D-2 governor new ? If not, they are cheap enough to just replace it. You can try to spray a very light oil into the intake of the compressor and gently tapping on the head with it running while doing this. 7 months idle may have them stuck. Edited Friday at 11:24 PM by Joey Mack More info needed 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587007 Share on other sites More sharing options...
Geoff Weeks Posted Friday at 11:26 PM Share Posted Friday at 11:26 PM If it is leaking back through the compresssor, it is the outlet (exh) valves. If the gov is mal functioning it can leak through the unloader. Try disconnecting the gov from the unloader and see if it will build. Caution: with gov disconnected it will never stop building air pressure, so don't run it all the way up. If it builds to over 60, shut it down and you know the gov is the problem. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587010 Share on other sites More sharing options...
cruiseliner64 Posted Saturday at 06:32 PM Author Share Posted Saturday at 06:32 PM Thanks for the replies.I disconnected the govenor but it still behaved the same.I tried a little light oil in the intake tapping with a hammer but again I had no joy.I think the head has to come off to sort this.The problem with taking the head off is the chances of getting a gasket over here is zero.Could the gasket be reused for a short time untill I can get a new one or could I cut one from heavy gasket material?.I thought it was a Midland compressor but not sure now.Heres a few pics of it see if you guys know what it is...Thanks again for all the help. Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587048 Share on other sites More sharing options...
Geoff Weeks Posted Saturday at 06:41 PM Share Posted Saturday at 06:41 PM Bendix Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587049 Share on other sites More sharing options...
Geoff Weeks Posted Saturday at 06:42 PM Share Posted Saturday at 06:42 PM Did you take the air gov off? (thing bolted to the left side of the compressor) and try it? I see way more gov problems then I do compressor problems. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587050 Share on other sites More sharing options...
Geoff Weeks Posted Saturday at 06:50 PM Share Posted Saturday at 06:50 PM What little I can make out it is a TF-501 Bendix. One of the most common for its day. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587051 Share on other sites More sharing options...
cruiseliner64 Posted Saturday at 07:01 PM Author Share Posted Saturday at 07:01 PM Yes I took the govenor off and it was still leaking back through the compressor.I know the pic isnt great but its the best shot I could get as its buried low in the frame.Im thinking its the unloader valves thats stuck.Many thanks for your replies. Paul Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587053 Share on other sites More sharing options...
Geoff Weeks Posted Saturday at 07:10 PM Share Posted Saturday at 07:10 PM If the unloader is stuck, it holds the intake valves open, not the exhaust, so it would not leak back from the tanks when the truck is turned off. It does sound like the exhaust valves are leaking . I would likely remove the outlet fitting and run the truck a max rpm and try and "blow out" any debris that might be keeping the valves from closing. Doing this will pass the max amount of air through the valves. Anything else will require pulling the compressor and/or head. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587055 Share on other sites More sharing options...
cruiseliner64 Posted Saturday at 08:09 PM Author Share Posted Saturday at 08:09 PM Thanks Geoff,I will try that tomorrow.If it doesent work Ill remove the head and see whats going on.I will let you know.... Paul Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587066 Share on other sites More sharing options...
mowerman Posted Saturday at 10:10 PM Share Posted Saturday at 10:10 PM Well these guys usually know a lot more than me. …im just a do it yourselfer but I had the same problem with mine around 20 years ago and a new governor did the trick best of luck 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587075 Share on other sites More sharing options...
Popular Post cruiseliner64 Posted 19 hours ago Author Popular Post Share Posted 19 hours ago Geoff,Joey I cant thank you guys enough for your tech support.The compressor is now working fine.I sprayed brake cleaner in the exhaust side and blew it out with shop air.I then ran the engine at high rpm and tapped the head gently.It blew out some debris onto a shop rag.After reassembly it worked just fine.Many thank again guys..... Paul 3 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587100 Share on other sites More sharing options...
Joey Mack Posted 19 hours ago Share Posted 19 hours ago Awesome !! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587101 Share on other sites More sharing options...
Joey Mack Posted 19 hours ago Share Posted 19 hours ago Id say a lot of black carbon like debris was restricting flow out of the compressor. Is there a pressure relief valve on the copressor head ? If not, i suggest adding one. We use 150 PSI releif valves. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587102 Share on other sites More sharing options...
cruiseliner64 Posted 19 hours ago Author Share Posted 19 hours ago 16 hours ago, mowerman said: Well these guys usually know a lot more than me. …im just a do it yourselfer but I had the same problem with mine around 20 years ago and a new governor did the trick best of luck I know what you mean Bob.I woukd say Im the same.I did serve my time as a mechanic but that was 40 years ago.I have restored a number of cars and pick ups over the years but this is my first big truck.Sometimes I need reminding of things I once knew but have forgotten.The guys on this site is just great for that.... Paul 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587103 Share on other sites More sharing options...
Joey Mack Posted 19 hours ago Share Posted 19 hours ago Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587104 Share on other sites More sharing options...
cruiseliner64 Posted 19 hours ago Author Share Posted 19 hours ago 2 minutes ago, Joey Mack said: Id say a lot of black carbon like debris was restricting flow out of the compressor. Is there a pressure relief valve on the copressor head ? If not, i suggest adding one. We use 150 PSI releif valves. Yeah a fair bit of black carbon debris came out on the shop rag.No theres no pressure relieh valve on the head,would I fit one to the outlet and adjust the pipes to suit?... Paul Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587105 Share on other sites More sharing options...
cruiseliner64 Posted 19 hours ago Author Share Posted 19 hours ago Just seen that pic now.I dont see a port to fit one on the head... Paul Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587106 Share on other sites More sharing options...
Joey Mack Posted 19 hours ago Share Posted 19 hours ago I wish i was familiar with that compressor, i cant tell from the pictures. On Bendix Tu-Flo and I think Midlands pumps too, there is a plug in the head on the air side not the coolant gallery. They can accept the releif valve. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587108 Share on other sites More sharing options...
Geoff Weeks Posted 19 hours ago Share Posted 19 hours ago I don't think the TF501 has that. Replace the elbow from the tube with a T fitting and a pipe to flare adapter and put the relief valve there. Also inspect or replace the copper line. If the head had carbon build up good chance the copper line does also. Be sure to use a high temp relief valve as the outlet temp can be quite hot 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587110 Share on other sites More sharing options...
Geoff Weeks Posted 19 hours ago Share Posted 19 hours ago P.S. glad it worked for you. disconnecting the line and running at high speed is kind of a "hail Mary" type situation, may work, but sort of last ditch effort before pulling the compressor. Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587111 Share on other sites More sharing options...
mowerman Posted 18 hours ago Share Posted 18 hours ago Yeah, Paul pretty much had the same background 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587117 Share on other sites More sharing options...
Geoff Weeks Posted 16 hours ago Share Posted 16 hours ago 2 hours ago, Joey Mack said: I wish i was familiar with that compressor, i cant tell from the pictures. On Bendix Tu-Flo and I think Midlands pumps too, there is a plug in the head on the air side not the coolant gallery. They can accept the releif valve. The earlier compressors in the Tru-Flo series, TF500,600, 700 and TF501 I don't think had the provision for a relief the TF 550 I believe does. It is a later compressor. I still have some 500 and 700 models, I'll have to check if I have a 501. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587120 Share on other sites More sharing options...
Geoff Weeks Posted 16 hours ago Share Posted 16 hours ago here it is from the horses mouth (Bendix) 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587121 Share on other sites More sharing options...
Joey Mack Posted 16 hours ago Share Posted 16 hours ago Yep. That was my point about the safety valve. Its good that you found that info.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76229-low-air-pressure/#findComment-587122 Share on other sites More sharing options...
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