Help me diagnos... 3 symptoms: Coolant, rough idle, strange noise.

MomoJeep

Basic User
Member
City
Seattle
State
WA
I just got my Jeep back from the shop. I have a rebuilt 258, 4.0L head, MPI. They put a new head on it, new lifters, new valves, etc.

However, (1) as soon as I started it, it seemed to idle a little rough in a "stumbling" kind of way.

(2) The noise. When I accelerate gently, it's fine. But if I hit the gas and put a load on it, a new noise shows up. Kinda like an exhaust leak, expect I checked all the manifold torques (good) and the manifold to exhaust pipe coupler as well (nuts were very tight).

(3) Also, after only driving around town for a few short trips, the coolant level dropped and coolant is not visible when looking inside the radiator. The radiator is brand new, the heater core only 1yr old. I check all hose connections and the radiator drain, etc. No sign of leakage.

Any ideas?
 

barrys

Scrambler Junkie
Lifetime Member
City
East Norriton
State
PA
I just got my Jeep back from the shop. I have a rebuilt 258, 4.0L head, MPI. They put a new head on it, new lifters, new valves, etc.

However, (1) as soon as I started it, it seemed to idle a little rough in a "stumbling" kind of way.

(2) The noise. When I accelerate gently, it's fine. But if I hit the gas and put a load on it, a new noise shows up. Kinda like an exhaust leak, expect I checked all the manifold torques (good) and the manifold to exhaust pipe coupler as well (nuts were very tight).

(3) Also, after only driving around town for a few short trips, the coolant level dropped and coolant is not visible when looking inside the radiator. The radiator is brand new, the heater core only 1yr old. I check all hose connections and the radiator drain, etc. No sign of leakage.

Any ideas?
3.....check your oil, hope it doesn't look like a chocolate milkshake.
 

Jeep Crazy

New member
City
Jefferson NC/ponce Inlet FL
State
Fl
I just got my Jeep back from the shop. I have a rebuilt 258, 4.0L head, MPI. They put a new head on it, new lifters, new valves, etc.

However, (1) as soon as I started it, it seemed to idle a little rough in a "stumbling" kind of way.

(2) The noise. When I accelerate gently, it's fine. But if I hit the gas and put a load on it, a new noise shows up. Kinda like an exhaust leak, expect I checked all the manifold torques (good) and the manifold to exhaust pipe coupler as well (nuts were very tight).

(3) Also, after only driving around town for a few short trips, the coolant level dropped and coolant is not visible when looking inside the radiator. The radiator is brand new, the heater core only 1yr old. I check all hose connections and the radiator drain, etc. No sign of leakage.

Any ideas?
Check your oil for water/ antifreeze
 

jammer1

Scrambler Junkie
Lifetime Member
City
Maple Hts.
State
Oh
If coolant in the oil, don't drive it or run the motor much. Anti-freeze will destroy the bearings. Contact who did the work on how they want to handle it. If oil level is correct an no water maybe you were lucky and the shop didn't get all the air out of the cooling system.
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
If coolant in the oil, don't drive it or run the motor much. Anti-freeze will destroy the bearings. Contact who did the work on how they want to handle it. If oil level is correct an no water maybe you were lucky and the shop didn't get all the air out of the cooling system.
Well damn, I already drove over 300 miles. :-/

I checked the dipstick today, oil looked fine. But would it show on the dipstick? Or do I have to drain some?
 

barrys

Scrambler Junkie
Lifetime Member
City
East Norriton
State
PA
Should show on the dipstick and sometimes the fill cap also.
 

Sfisher

Basic User
Member
City
El Dorado Hills
State
CA
(2) The noise. When I accelerate gently, it's fine. But if I hit the gas and put a load on it, a new noise shows up. Kinda like an exhaust leak, expect I checked all the manifold torques (good) and the manifold to exhaust pipe coupler as well (nuts were very tight).

Any ideas?
I have the same the setup and have a whistle from the air filter sucking in air. Its loud enough to be clearly heard when hitting the gas. When the whistle goes away, the filter needs cleaning or replacement. Just a possibility.
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
3.....check your oil, hope it doesn't look like a chocolate milksha

I have the same the setup and have a whistle from the air filter sucking in air. Its loud enough to be clearly heard when hitting the gas. When the whistle goes away, the filter needs cleaning or replacement. Just a possibility.
I get that annoying whistle too. Mine has never gone away. At least it's like an indicator for you to check your filter. What kind of filter do you have?
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
Should show on the dipstick and sometimes the fill cap also.
Correct me if I'm wrong.. If the head gasket was leaking, the coolant could go directly into the oil galley where the pushrods are. On the other hand, the coolant could go into a cylinder and not directly to the oil. If in the cylinder, wouldn't most of it end up going out the exhaust pipe (and causing the engine to run a little funny maybe?)?
 

jammer1

Scrambler Junkie
Lifetime Member
City
Maple Hts.
State
Oh
Into the cylinder you would get white smoke and the exhaust would smell like anti-freeze. Into the oil, depending on the amount (example if you lost a quart of coolant into the oil would raise the oil level, like adding a extra quart of oil on a oil change). If you lost a quart of coolant into the oil you should see it on the dip stick. If you had air is the system you could just be a quart or so shy on coolant, Could also run hot on the temp gauge till the air pocket gets to the radiator.
 

Sfisher

Basic User
Member
City
El Dorado Hills
State
CA
I get that annoying whistle too. Mine has never gone away. At least it's like an indicator for you to check your filter. What kind of filter do you have?
This one. Would like to have a factory air cleaner but the wish list is ,infer than my bank account!1617715156178.jpeg
 

bigwalton

Alaskan Postal nutjob
FORUM MANAGER
SOA Member
City
Dexter
State
MI
I was going to say that they didn't sufficiently burp the coolant too. If it's not leaking out, the oil doesn't look like a milkshake and the exhaust isn't white smoke, I'd top off the radiator and see what happens. Just keep a close eye on the oil condition.

I always described exhaust noise as "fluttery" where the sucking noise of the filter or a vacuum leak is a "whistle". I'd have a hard time ever confusing the two but maybe you have a vacuum leak? Could explain both the noise on acceleration and the rough idle. \

For exhaust, is there any chance that the exhaust manifold is cracked? The removal/reinstall process maybe too much for it?

On the vacuum side, check all those connections/hoses. Again, removal/reinstall could have cracked something. Then, when dead cold, start it and quickly (before it gets hot) shoot some starting fluid around various vacuum connections and the base of the throttle body, see if the idle picks up from sucking in the fluid.
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
I do think the coolant was a burping issue. I took three top off but seems to be holding now. No problems in the oil. Exhaust looks normal.

Somehow the overflow reservoir is well above the full mark. I'll probably suck some out to make it right.

The idle is still off. Runs smooth above idle, but idle feels like it's dropping a cylinder a little.

The noise: I don't think it's an exhaust leak. Here's why: it doesn't happen at idle. And doesn't seem to happen at the higher end of the RPM's in a given gear. But it does happen at the low RPM end of a gear, and then only when I accelerate. Could be like a "pinging", expect not in all cylinders. It's more like ONE cylinder is having an issue... hmmmm!?
 

jpnmaine

Active member
Member
City
East Wilton
State
ME
Overflow reservoir. If it fills again and you are still burping the coolant system could indicate head gasket issue pressurizing coolant system.
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
I think this is resolved. My worst nightmare would have been a bad head. Next worst, head gasket. Turns out these symptoms are probably not all related. The coolant was due to a combination of a hose connection not tight enough (no visible drips, but small amount of coolant must have been escaping while driving (engine hot). Overflow due to faulty (4 month old) radiator cap.

The rough idle and engine noise were due to a bad fuel pump. Very low psi in the fuel rail. That would explain pinging while accelerating at low end of rpm band (highest fuel demand combined with engine closest to lugging). But I still don't know how it explain the rough idle(?). If there was enough fuel to run well at highway speed, how is there not enough for a smooth idle!?
 
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