Hi guys,

I came back from a big trip some days ago with my 4.9L 300 motorhome, there was a big vacuum leak at the EGR valve. I tried to make some tempory gasket with RTV and let it dry for 2 days. It worked great, the engine was running better than ever, but after about 1 hour of driving, the gasket was completely gone, I was on the highway and the temperature gauge went really high before I realise it. So I stopped to find that the RTV didnt last. After that, the engine then suddently started to shake a lot on idle. I feel it inside the motorhome. And it's better on high RPM but I still feel it.

I guess I could have damaged the internal engine because of the 1 minute high heat right? It's still runs fine but there is a deep intermitent shaking.

Also, I started the engine today and the oil gauge indicates low pressure even if the oil pan is full.

What do you think?

Thanks.

 

RTV does very bad things when sucked into the oiling system. I can't think of any way to even start on this one. This will bring it back to the top and maybe you'll get some help.

 

I don't know if RTV got inside the engine but it could be possible. Wouldn't it just get out by the exhaust after a couple of highway miles? I mean, if it burned on the EGR valve and made like small white non sticking particules looking like sand. It would do the same thing inside the cylinders? So the compression would push it out by the exhaust system, no?

If it's not the RTV. What does high temperature usally breaks so it makes that shaking sympton?

Thanks.

 

same here...not sure where to start. but since you're not getting a lot of response, i'll give it a whirl.

so- your RTV got sucked into the EGR, which re-opened the vacuum leak, which leaned out your air/fuel mixture, and caused the engine to overheat.

you asked what high heat would normally do to damage an engine...my first guess would be a warped head. but you say the vibration is intermittent, which muddies the water.

so, three questions:
1. how hot did it get?
2. how long was it hot?
3. how often do you feel the vibration?

 

Hi,

Thanks for your answer.

1. The temperature gauge was on H
2. For about 2 minutes at about 2500 rpm
3. The vibration is really for here at idle and it's really intermitent but never stop. I mean, it's not always vibrating at the same time.. sometimes there is a vibration after 3 seconds, sometimes after 10 seconds, etc. But it's not going away.

I did take a drive yesterday and the EGR valve is still leaking because my EGR plate is bend.. I did not give attention if it was still vibrating this morning but I think it was less intensive. Probably the RTV is going away. It was the orange RTV, the cheap one.

Except for the vibration, the engine is running really fine.

Thanks.

 

i wonder if the vacuum leak is messing the mixture up enough that the engine is knocking.

i'd say you should apply a permanent fix to the EGR leak, then see where you are.

Engine knocking - Wikipedia, the free encyclopedia

 

You have more than one problem, probably just a start from the egr.


What year is the motor? carbed or efi? that will help determine what step to take.


I think the over heating will probably not be an issue, unless you kept driving until it quit.