79, 304 cooling problems

[TGCJ5]

Hello All, I’m new to the site & not computer expert.
I am having cooling problems w/304 amc engine on a 79 CJ5 SA mostly original. Any help will be appreciated.
Rad. cap 16 lds, new rad., new hoses, original water pump & it’s turning & flowing good, checked thermostat & opening at 195 degrees, 4 blade fan w/ no fan clutch, have fan shroud. Installed a VDO temp gauge & sender. Wire running from sender straight to gauge. 45 mph runs right at 195 to 200 degrees. Run up to 60 or higher mph engine runs approximately 210 to 215 guess. Needle doesn’t go pass the second 0 on 200 number. Hope you understand that. Have flushed out block & heater core & rad. 3 to 4 times. What am I missing?

 

[jp360cj]

If it never gets over 215*F then you aren't overheating. 210*F Thermostats aren't uncommon with these engines.

Did it previously stay closer to the 200* mark all the time?

 

[Lumpy Grits]

:ww:

215* is not over heating. The t'stat isn't even full open, till about that temp.
LG

 

[TGCJ5]

It’s hard to know. I used the original cold-hot no numbers gauge. Temp & fuel gauge kept quitting so I’m replacing with better gauges. Fuel gauge has to be a specific ohm range. Didn’t know if temp gauge was in the same type perimeters.
It isn’t blowing out the overflow, just hotter than 195 regulated thermostat. Only had the jeep for 3 years.

 

[Lumpy Grits]

The ele. temp sender and oil pressure sender have to be 'matched' to the gauges for accurate readings.
Also-Think hard about adding a dedicated GND wire from your dash panel, to the battery NEG(-) post.
The biggest electrical issue with these old CJ's, is the GND circuit.
Also-Mount your battery NEG(-)lead that goes to the block, to the top bolt of your starter.
LG

 

[TGCJ5]

Ok. Thanks. I didn’t know the oil pressure & temp gauge had to be matched set. I’ll have to get a VDO oil pressure gauge, cockpit, to match. The temp gauge has a dedicated ground wire to the firewall. I’ll change it to run straight to the battery neg. post. I’ll have to change the main neg battery lead wire to the starter too. I have it bolted to the passenger head. I do know the old org. Temp & fuel gauge use the 5 volt jumper wire in the speedometer cluster to work properly. I’m finding out the electrical system is finicky.

 

[jp360cj]

Ok. Thanks. I didn’t know the oil pressure & temp gauge had to be matched set. I’ll have to get a VDO oil pressure gauge, cockpit, to match..

The oil and temp gauges don't have to be matched to one another.

What LG is saying is that the temp gauge must match the temp sending unit and the oil gauge must match the oil pressure sending unit. Same with the fuel gauge and any other electric gauge. You can either match the new gauges to the OEM sending units, or get new sending units to match the new gauges.

 

[TGCJ5]

Thanks jp360cj. I miss understood. I’ll put in a new sending unit with any new gauge I get. That way I know the gauge has correct sender. Temp gauge has correct VDO sender, or what was recommended.

 

[Lumpy Grits]

Have installed several of these for friends over the years, no issues that I know of.
Comp II Performance Auto Gauges

TNX 360, for the clarification to my post.

LG