StoneandSteel Posted March 13 Share Posted March 13 On my ai400 the valve bridge on cylinder #1 and #6 keeps jumping off even after doing a full valve adjustment. It will run for a few days but eventually I notice a decrease in power and a lot of white smoke which tells me the bridge came off again. I don’t see any noticeable damage to the valve springs or rocker arms. Any idea why this is happening? Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/ Share on other sites More sharing options...
fjh Posted March 13 Share Posted March 13 So is it possible you have a sticky valve on one cylinder ? one slow returning valve could cause what your seeing! I have only seen it happen once and never resolved the issue! Note be sure to replace the rocker bolts these have had breaking issues in the past! Have you checked the push rods for straightness! Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571252 Share on other sites More sharing options...
Joey Mack Posted March 13 Share Posted March 13 Did you run the valves by the book, or the same way as Caterpillar or John deer 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571254 Share on other sites More sharing options...
Solution Joey Mack Posted March 13 Solution Share Posted March 13 Have you looked up at the cam lobes recently? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571255 Share on other sites More sharing options...
StoneandSteel Posted March 13 Author Share Posted March 13 I followed the valve adjustment procedure per the manual and a video off of YouTube on an ai400 with a Mack mechanic. I did pull the push rods and roll them across a flat surface. They seemed fine. I’m going back into the engine today to start all over from the beginning and try it again. I’ll check all the suggestions so far. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571262 Share on other sites More sharing options...
StoneandSteel Posted March 13 Author Share Posted March 13 Found the problem today. It’s for sure 2 bad lifters and I would expect the cam should be replaced as well. My question now is, does the engine need to come out or can I do the repair in-frame? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571280 Share on other sites More sharing options...
Joey Mack Posted March 13 Share Posted March 13 In frame. You will need a jack or a jig to hold the front of the engine up a few inches for support, and to let the cam gear clear the front x-mem. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571281 Share on other sites More sharing options...
StoneandSteel Posted March 13 Author Share Posted March 13 Thank you for the info. I’ll get started ordering the parts and tearing her down. Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571288 Share on other sites More sharing options...
Joey Mack Posted March 13 Share Posted March 13 This engine has lifters with ceramic rollers. They will crack very easily when installing the cam. Steel lifters are available. Without insulting you, i assume you havent done one of these cams based on the question about inframe or out. Myself , i have most of the essential tools to do this job. I strongly suggest you read the Mack procedures. Most of the job is common, but there are a few procedures that have to be followed. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571290 Share on other sites More sharing options...
StoneandSteel Posted March 13 Author Share Posted March 13 1 hour ago, Joey Mack said: This engine has lifters with ceramic rollers. They will crack very easily when installing the cam. Steel lifters are available. Without insulting you, i assume you havent done one of these cams based on the question about inframe or out. Myself , i have most of the essential tools to do this job. I strongly suggest you read the Mack procedures. Most of the job is common, but there are a few procedures that have to be followed. You are correct, so any input or advice are much appreciated. Someone said that the E7 and the ai400 were actually the same engines. I only ask as I begin my search for the rebuild kit for cam and lifters. Any thoughts on this question? Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571301 Share on other sites More sharing options...
Joey Mack Posted March 13 Share Posted March 13 P.A.I. has a quality product. As you go forward, post questions. Like about front hub and seal and cam gear removal and install.. you will need am oven to bake them. I wish i had extra cam books. I had a bunch, but gave away most of them.. Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571305 Share on other sites More sharing options...
880joe Posted March 14 Share Posted March 14 It's a good time to replace the AI emissions cam with pre emissions CCRS cam 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571310 Share on other sites More sharing options...
fjh Posted March 14 Share Posted March 14 15 hours ago, StoneandSteel said: You are correct, so any input or advice are much appreciated. Someone said that the E7 and the ai400 were actually the same engines. I only ask as I begin my search for the rebuild kit for cam and lifters. Any thoughts on this question? Do you have a press? As joey stated there are procedures the cam gear is sweated on ! If you don't have an oven you can use a torch! And start from the out side of the gear and work to the center slowly heat it up to around 475 I believe not positive on the temp and don't forget the cam retainer you'll be hating life if you do! 😡 Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571329 Share on other sites More sharing options...
Joey Mack Posted March 14 Share Posted March 14 Yes on the temp. With a torch you need to be even or the gear will warp Quote Link to comment https://www.bigmacktrucks.com/topic/75278-%E2%80%9807-mack-ai400/#findComment-571332 Share on other sites More sharing options...
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