I think I have an Over Heating Problem

[AMC86Kid]

ok so tell me what you guys think about my 3.4 liter 

here's the pics i took with an IR Thermometer

 

this is the temp on the (temp sensor)

 

 

here's the temp on the block where the top radiator hose connects 

 

here's the temp in the hole in the header valve cover 

 

and here's the new 16 inch fan i installed it blows towards the engine 

 

so i ran the motor for about 15 to 20 minutes and i feel like its getting to hot what do you guys think 

is the hole in the engine valve cover suppose to be that hot ?

[Jeep Driver]

If you're aiming at an exhaust valve..............probably, yeah. 

 

I'd run that engine at 180............my guess is you have a POS Stant 195 stat. 

 

Get a MotoRad 180.

[Jeep Driver]

Good shroud, BTW. 

 

You could have done with a few less holes..............however...........people don't think to relieve the hot spots..........corners are hot spots. Turbulence is actually created where air cannot flow. 

[AMC86Kid]

i actually don't have a thermostat i am currently running it without one

i got a new 180 just havent put it on yet 

 

what temp should i be with no thermostat

and any ideas on what can i do to get the temp down ?

[Jeep Driver]

Install your stat, you need to slow down the flow and give the coolant some time in the radiator, it's there for a reason. 

[AMC86Kid]

ok i will try that out and see how it goes 

[omega_rugal]

You are probing the hottest spots in an engine...

[AMC86Kid]

so ideally with a 180 thermostat

i should not be getting over 200 degrees on the engine block with the IR thermometer 

does that sound right to you guys 

[AMC86Kid]

ok so i put in the new thermostat and ran the engine for about 20 minutes 

the IR thermometer on the temp sensor read 207 degrees 

and after the 20 minutes went by i had to shut the engine off because it started to slow down 

and it started to make a weird knocking sound under the passenger side valve header cover  

 

any ideas on whats wrong or what i can do to check it out 

i will take a look at it again tomorrow and maybe run it a little more to see if it still does the sound

so far not good i sure hope i can figure it out  

[Ωhm]

Different vehicle but same problem. Look for air bubbles in the coolant recovery bottle, if equipped. I could see one bubble every one or two seconds, took about 20 minutes before engine started making noises and major overheat. In my case, it was the head gasket.

[AMC86Kid]

do you think i have to replace my head gaskets and the my overheating issues damaged them ?

[Ωhm]

In my case a faulty head gasket (was a known problem) caused my overheating problem. Can't say which came first for you, overheating, then head gasket or head gasket, then overheating.

[AMC86Kid]

ok i will run it tomorrow and see if i get any bubbles not sure with my radiator cap being rated at 18 lbs 

but its worth a try and if i do end up replacing my head gaskets then i have to go back to 

figuring out why my engine keeps over heating (so i don't blow the new ones)

maybe my radiator is not big enough I'm using the one from the 2.8 

i guess i could try a bigger radiator that should cool down the coolant better id imagine 

do you know what temp your motor runs at Ohm?

[Green Mesa XJ]

Radiator is plenty big enough as long as it is clean enough to have proper circulation. If it’s clogged it would cause it to run hotter. I’m not sure what kind of upgrade would fit in the same spot, probably something for the 2.5 XJ/mj.

You said it slowed down, how so? RPM?
The carburetor may be out of adjustment for operating temp idle. I think it can be adjusted easily enough if that’s the case.

The noise is bothersome, If I were to guess without actually seeing or hearing I’d wonder if the noise was a bent push rod or lifters clatter do to low oil pressure. Since it’s rebuilt might be a good idea to check the push roads are adjusted correctly or at least nothing looks amiss.
If you do more testing oil pressure can tell you a lot along with compression testing. I’m thinking oil pressure in case the bearings took a dive.

Why do you keep thinking the motor is overheating? Did something else happen? Something possibly wrong with the engine rebuild?
Just wondering because since the beginning you were concerned about how hot it got.

Generally speaking iron head and blocks are more forgiving than aluminum head engines as Long as the gaskets are properly installed. You can run 195-210 and be fine, although my 2.8 seems to run 180-190 (haven’t tried IR temp reader to verify, didn’t have those in the rickety past or else I would have. )
only time I ever had the temp spike was high altitude and really pushing it to climb, other time was when the water pump died.

I would hate for you to have to tear that engine down to fix it.


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[Green Mesa XJ]

Almost forgot is the timing correct?


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[Ωhm]

I'm not sure if you have bad head gasket(s) or not. Didn't mean to imply that. I had a bad head gasket with bubbles in my overflow bottle, causing my overheating problem. 18psi cap seems a little high to me. Fine line between raising pressure to control overheating and maximum system pressure (all engine gaskets). Does coolant recovery bottle work properly? Could engine be running extremely lean (check spark plugs)? Don't know engine temps using IR reader. Are you using a 50/50 mix? Anti-freeze is also a coolant.

[AMC86Kid]

Yes Green Mesa after i had ran it for 20 min it started to slow down in RPM

it just wasn't running as smooth and as steady 

i took the valve covers off to see if something was loose and i didn't notice anything 

i don't see why the timing would be wrong after all these test runs that have gone smoothly 

 

i guess i will run it with no thermostat again for 5 minutes just to see if i get any bubbles with the radiator cap off 

if no bubbles then i will put the thermostat back on and run it and see how long till i get the sound back 

if i do get the sound back then i will try to record a video of it to show you guys "i would really hate to have to take this whole engine apart"

and i will probably have to put it up in a new post since its not about "over heating" or at least i don't think it is 

[AMC86Kid]

ok so here a link to the radiator coolant flow after i took the thermostat off

i didn't really notice any air bubbles other then the air that was trapped in the upper hose from taking the thermostat off

https://streamable.com/wyrr2

the engine did not make the weird sound (this time only ran if for like 3 minutes i guess my head gaskets are good)

so i will let it cool down and then put the thermostat back on then run it for 20 minutes again and see if the sound comes back 

[Green Mesa XJ]

The thing about the bubbles is you could still be burping out air. Just as part of the normal process of having swapped the engine out. air gets trapped and can take time to get out, also pin hole leaks and lose clamps can cause it too.


I’ve had cars with blow head gaskets, it’s not subtle when it happens, not a few bubbles it was belching up huge amount of air and the temp would fluctuate between too hot and normal as air pockets circulated past the temp sensor.

That’s what a normal BHG does followed by white smoke like you are electing a new pope.

Then there is seeping BHG where minuscule amounts of coolant escape to the combustion chamber, looking for signs of this can drive a body nuts because any little change might indicate it when tests don’t show it. Well except for oil test where you send it off for analysis.

Overheating, if that is what is happening, can be a old radiator, bad water pump, something else in the plumbing keeping the circulation off.
It can be the fuel mixture is too lean.

The timing can be way off and the engine still runs. It might or might not drive for $#!&, it’s kind of one of those things you’ll feel driving it.
Timing off can cause it to ping. And other noises depending how bad it is off.
The 2.8 (in general ) is supposed to be set for 10 degrees before top dead center mark, I think mine says 17 degrees BTC on the sticker. The 3.4 didn’t uses distributors so whatever you are using now was added to the motor after the rebuild. If it was done correctly I wouldn’t give it a second thought cause it not going to change except with vacuum advance if that is what your jeep had.

That motor shouldn’t have blown the head gaskets easily unless it was done wrong, or really and truly ran past 250-280. I don’t necessarily trust the rebuild was correctly done, but I wouldn’t jump to the BHG ship just yet

The rpm dropping is probably normal for it reaching operating temp and opening the choke all the way. You should just have to bump it up a little to get 700 to 1000 rpm curb idle.
Engine dropping rpm also drops oil pressure. Oil pressure should be around 10psi at idle and 50-60psi at 2000 rpm. My old 2.8 has great pressure at idle 20 to 30 psi, which is partly why I never swapped it out. It never failed outright. I know it was high milage engine when I bought it (probably not the original motor...maybe) and I put another 100,000 miles on it.


That auto zone link ought to have the instructions to bump up rpm..,,
yes it does
http://www.autozone.com/repairguides/GM-S10-S15-Sonoma-Pick-Ups-1982-1993-Repair-Manual/IDLE-SPEED-AND-MIXTURE-ADJUSTMENTS/Carbureted-Engines/_/P-0996b43f8038eee0

All of this is crap you’d never normally have to do just swapping the motor. Not knowing the history of the old motor or parts you are using is kind of like starting from zero because any questionable setting might have to be rechecked even if it’s not normally done in diagnosis.

BTW if the head gasket really is just seeping a retorque to spec of the head bolts might reseal it. Long shot but it can work.

But like I said the head gaskets maybe fine, you’d see oil level increasing and eventually muddy oil, as well as air bubbles in reservoir tank, and white smoke when it really got serious letting coolant in to the combustion chamber.
Does the reservoir work? It should increase with the engine reaching temp the decrees as the coolant cools.






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[AMC86Kid]

Green Mesa the coolant reservoir dosent even really move

like i said i have a 18-lbs radiator cap its the correct one for the 3.4 ltr maybe thats why it runs so warm 

but any ways i will post a new link here for the new video on the engine slowing down 

[Ωhm]

10 hours ago, Ωhm said:

Does coolant recovery bottle work properly?

 

[AMC86Kid]

i have the coolant recovery bottle hooked up correctly 

and i put fluid in it as well 

 

 

oh hers the link for the new post :

https://comancheclub.com/forums/topic/53998-34-ltr-engine-stalling/

[Ωhm]

Hooked up correctly and operating properly are two different things. Does coolant level rise and fall within the bottle as temperatures rise and fall within the radiator? Disconnect hose at radiator and blow back (air hose) towards coolant recovery bottle. Make sure cap is for a coolant recovery system.

[Strokermjcomanche]

Just my shot in the dark ........ 

 

the 2.8 had a v-belt setup and you're running a serpentine belt( with the 3.4 or 2.8 pump/pulleys?) , is the rotation /  direction of the water pump flow correct ? 

[AMC86Kid]

how is the cap on the recovery tank suppose to be cause mine is cracked 

is it suppose to just sit or is it suppose to be completely sealed ?

 

also i looked and i do believe that the water pump is moving the flow correctly