So I just got a new to me 1999 Ram 1500 5.2L with 57K miles on it this week and noticed that when running low grade fuel I would get spark knock and it felt a little low on power. After talking to some people in the non tech section about it I decided to check for a failed plenum gasket. I pulled the air box off and looked down the throttle body and didnt see much but it looked like a tiny bit of oil. I watched a couple of videos about a failed plenum and decided to check vacuum at the pcv valves, and holy crap it has more suction than my shopvac. So I see a replacement plenum gasket in my future. Is there anything else I need to do while I have it apart? Is it worth it to go ahead and replace the water pump while in there?

Link to my other thread. Moving to here because it is now a tech issue.
https://dodgeforum.com/forum/2nd-gen...ack-again.html

 

I wouldn't just change the gasket, I would change the plate to an aluminum plate. I personally would at least do the timing chain. I didn't change my water pump and its still going (although I think it's starting to go out) and that was a year ago.

 

I ordered the Hughes plenum kit. Could a blown plenum gasket cause excessive vacuum from the valve covers?

 

That would be a question for @Hey You I always did the oil filler cap trick

 

Yes. The plenum will draw vacuum from the valley between cylinder banks, and that is open to pretty much the entire engine. Blown gasket will make the engine run a bit lean, which leads to spark knock, another contributor is the oil the intake is now free to suck in, and burn, which leaves carbon deposits in the chambers, and on the valves, which contributes to hot spots, (another great cause of spark knock) and low compression from fouled valves.

The aluminum plate isn't required, but, it's not a bad idea either. The real issue is the bolts are too long, or, the gasket is too thin.... Shortening the bolts, and using a good quality gasket is all it really needs. Some folks talk about expansion rates of dissimilar metals.... (aluminum intake vs. steel plenum plate), but, I did the math, and given the materials involved, and the temperature range, the difference in movement is measured in thousandths of an inch, and single digit ones at that. Dissimilar metals is not the problem. The bolts are.

Your truck is pretty low mileage though, isnt it??? I would be tempted to do water pump, and timing set anyway. (double roller chain and gears please. ) Also, do the cap/rotor/wires, and plugs if you don't know the last time they were changed.... It won't getting any easier than when you have the intake out of the way.

 

Yea, its crazy low miles for a 20 year old truck. I went ahead and got some plugs (NGK V-Power copper), cap and rotor, and plug wires. I'm still torn about water pump and timing chain. Its got so few miles I'm not sure it needs it.

 

Timing chain might be ok, but, the water pump is still 20 years old. It's like six more bolts to change it out, since you are removing the intake anyway. But then, once the pump is off, it's only six more bolts for the timing set as well.

 

I went ahead and ordered a double roller timing chain set and water pump. Might as well do it while it’s apart.

 

You will not regret the decision.

Gotta be careful pulling the timing cover itself, as it also seals to the oil pan gasket at the bottom. (and there are two bolts going UP thru the oil pan into the timing cover as well.....) I broke it loose at the top first, and then tilted it forward to break it loose from the oil pan seal, I managed to NOT tear it up that way.

When you get your timing gasket set, get the normal one, NOT the one with the sleeve for the balancer. I really don't like those, and have had zero success installing them. (maybe it's just me. )

 

So I got my plenum replaced with the Hughes kit and holy crap what a difference. No pinging even when pulling my trailer up a hill, and the truck feels like it has so much more power now the the plenum isn't leaking. Very happy with the results!