Hey all. I have a 1991 Fleetwood Bounder motorhome that is having engine trouble. It is a Chevy 454 engine. I did a half assed compression check and found the following the back 3 cylinders on the passenger side have 50, 0, and 50 for the compression. Keep in mind that I am not a mechanic and I did not remove all the spark plugs when i did the test. I just removed one at a time after replacing the spark plugs and plug wires. my question is that since the compression is bad on those three cylinders is it possible that I blew a head gasket? No, I do not seem to have milky oil and I also took out the plug on the 0 cylinder and using a endoscope I can see the cylinder head is moving up and down. I am really hoping not to have to remove the whole engine as doing so would be more then this thing is worth by a couple thousand dollars. I also have positive pressure pushing out the dip stick. Is it worth it to either try to do the head gasket myself(I have not done one yet) or pay someone to do it for me? I need a mechanic's opinion on this.

Thanks for any help you can give.

James

 

Sounds like a head gasket and if you do it they both should be done and definitely get a complete compression test of all 8 cylinders with all plugs removed. In the low compression cylinders you should do a wet test. That is where you squirt some motor oil in the cylinder and run the compression test again. If the pressure goes up, that means the piston rings are bad and that means a complete engine tear down. If the pressure remains the same, that means the problem is the heads or head gaskets. You may have valve problems causing the low compression. DO NOT remove heads and just do the head gaskets. The heads should be sent to a machine shop for resurfacing and a valve job with new seals and guides and checked for cracks.

Here is the caveat. If you have no mechanical background, no knowledge and no correct tools, leave this job alone and let a qualified tech do the work. There is also the need to inspect the cam and push rods and lifters while apart and replace in sets as needed.

 

I do most of my own work so far. I usually don't work on engines other then to do injectors, spark plugs, coil packs, and stuff like that. about the most I have done is taken a valve cover off and replaced it to get rid of a leak. My thoughts are that on this the if the head gasket failed in two spots(between the two cylinders) that could be the reason why 4 and 8 are sitting at 50 psi and 6 is at 0. I do have the space(barely) to pull that head out through the dog house. Anything on the lower end would end up in a full engine pull. I can't pull the oil pan. when I did the compression test I basically pulled the main line to the distributor so that the engine could not fire off and did each cylinder one at a time. It starts much better now but I can not really move it to test for power yet. I also have pretty much most if not all the tools to do it myself as well. The only really bad thing is that I am not sure I can get my torque wrench in to torque it down. that should be interesting. I know a lot of the theory but not the practical on this.

 

Motorhome engine work sucks. I have dealt with that here in the PNW when I was running shops because this area is a haven for motorhomes. I would do anything to not work on an engine in a motorhome. You need to do the wet test compression check to pinpoint the area that is causing the problems. You could do a beautiful job on the heads and still have piston ring problems that means you wasted your time.

 

Yeah, I will do that. I will have to go in through the wheel well for the back two cylinders. Ugg. It is a bit of a contortion game to get in there. This would also be easier if it were on cement instead of grass. Where in the PNW are you? I am down by Centralia.

 

I am in Eugene (Pewgene) Oregon.

 

Ok. I will try to do a wet test after thanksgiving. while I am ok with using the endoscope that I picked up cheaply to look at that cylinder I don't know what else to look for other then the piston going up and down.

 

You can't see broken piston rings until you remove a piston but the wet test tells you if you have ring problems. The oil that you put in that cylinder before you do the wet test compression test, will seal around the broken rings and the compression will come up. If the compression stays the same, the problem is in the heads and head gaskets.