2004 Disco with rebuilt engine. NEW: cam, pistons, rings, bearings, rods, tappets, water pump, oil gears, radiator, low temp thermostat, wires, plugs and pcv valve. Just got it running about a week ago so I am still in the break in period with only 300 miles on the engine. The short block was professionally built on a bare block that had been cleaned up and pressure tested. Valve seals done and heads professionally milled.

Symptoms: Engine is running around 221 at idle and between 212 and 221 on the highway. When accelerating, the engine sounds like a diesel with a bit of a rattle and a high frequency chirp. Sound is not noticeable unless accelerating. Sound does not appear localized to a specific part of the engine.

I realize I might have two unrelated issues here but have posted them both together so everybody can see all the info.

Whats Been Done: Coolant system has been bled while cold and topped off for the past couple of mornings with no apparent change. PCV valve was replaced due to a (unrelated?) P0441 error. Cats have been checked and appear solid.

Next Steps In Order Of Priority

1. Replace fan assembly. This should help my cooling and I have also read where people have said the viscous clutch fan creates a diesel like noise.
2. Test thermostat. This was a Britpart 180 stat but I need to boil it to make sure it is functioning properly. Replace if necessary.
3. Check oil pressure: No oil light but as Disco Mike has stated, if there is a noise coming from the engine, check the oil pressure before you start digging around in the engine.
4. Check flexplate: I read on the forums that a cracked flexplate can make this type of sound. I checked it before I put it back on and it looked solid. I will inspect again but not sure it has anything to do with the heat.
5. Exhaust leaks: Some people have suggested this but I read that the exhaust leaks make a "chuh chuh" sound - not a higher pitched diesel rattle. Will retorque exhaust manifolds.
6. Oil pump: I replaced the rings but didn't change out the front cover because it appeared to be in good shape. This would be a fair amount of work and I won't go here if the oil pressure looks good.
7. Valve noise: Valves were ground and seated when the heads were done so not sure this could be it. This one is lower priority. Maybe try a thicker oil to see if that quiets things down before I start pulling the valve covers off.
8. Rockers? Same old set. Worth exploring once heat issues resolved and oil pressure verified.
9. Rod issues? Unlikely - there are new rods and lifters installed. I guess it is possible but its low on my list.
10. Slipped Sleeve: I'm skeptical of this. The block and sleeves were solid. Not sure there's much I can do to prove or disprove this except take the heads off so I am putting this at the bottom of the list for now.

Am I on the right track? What else might I be missing?

 

Regarding the "sounds like a diesel" symptom, in the case of my truck that was caused by a failed exhaust manifold to down pipe gasket. It made the noise only under acceleration. The gasket is an $8 part, and perhaps I was lucky but in my case the nuts came off the studs with no trouble. Good luck.

 

As far as temps go, You're on the right track with the thermostat. There have been a lot of posts on here about Britparts labeled as 180 but actually not. Your temps look exactly like a stock stat would look.

That being said, do keep checking through the bleed hole for air until you see it full.

I also had an exhaust leak at the down pipe, not a chuh chuh, higher pitched rattle sound. Retorque your down pipes in addition to your manifolds. I had the chuh sound when it leaked from the joint after the cats ahead of the silencer and also at the joint in the Y after the passenger side cat. Had to get a better clamp for that to work. The one Magnaflow shipped was crap. You need the flanged one:

 

Definitely keep checking the bleed port at the T connection for air and refill. I checked mine once and filled it up thinking the air problem was sorted. NOPE! I had to keep checking and refilling on a cold engine at least 4 more times to get the air out.

Also I didn't see you mention what kind/brand of coolant you are using.

 

I hope you are right about this. Seems like an easy fix!

 

very cool. Thank you for the the advice! Will let you know how it goes.

 

yep I will keep checking on this. Don’t want to start a flame war but I am using Dexcool.

 

If you have a shop vac, it's pretty easy to check for leaks in the exhaust system by connecting the shop vac from it's outlet to your tail pipe so that the shop vac is blowing into the tail pipe. You can then use a spray bottle with some soapy water around the exhaust connections to see where you get bubbles. Sometimes you don't even need to spray the soapy water;you can hear and feel the leak.

 

that is pretty cool! Doing that tonight for sure!! Thanks!

 

I think there are YouTube videos showing how to do it.