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1976 with 318 overheating

Cltjones

Member
Can idle all day but when under load overheats any ideas welcome
 

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tucker mule

New member
I'd suspect a thermostat first,(cool upper radiator hose) then maybe a bad radiator cap. Possibly a radiator hose has separated on the inside. Oil in water or water in oil ??
 

Track Addict

Bronze Member
GOLD Site Supporter
Thermal temp gun on some different cooling sections at overheat would be telling.

A new thermostat and cap is cheap troubleshooting.
 

Tye one on

Member
I would suspect thermostat as well but what temp do you consider overheating? Is it blowing coolant out or boiling?
 

PJL

Well-known member
Is the fan pulling enough air? Does it need a shroud? Is this a newly developed problem?
 

srs001

New member
I would be willing to bet thermostat as well. Have had a similar issue my self mine was boiling over coolant. Changed thermostat and all was well you can test your thermostat in a boiling pot of water to make sure it is opening and closing.
 

Cltjones

Member
Thanks, Have changed thermostat 160F, Rad Cap new, Rebuilt engine,, New rad hoses. Electric Fan on outside pushing air thru rad toward engine has shroud, It starts going past 210F not boiling. Will use Thermal gun tommorrow.
 

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un hook electric fan----cover rad. with a trap----start the cat with cap. off when it heats up watch in rad. to see if there is water movement when thermostat opens-----I have also seen the block air bound----one trick to a new thermostat is drill a small 1/8 hole on the outside edge to allow air out of the block and up into the upper rad. house filler neck-----and not being a wise guy------but------- when u had the motor out and most of us have to repaint everything----is the fan blowing toward the motor----is the fan reinstalled in the right direction
 

Cltjones

Member
Will give it a try covering the red with a tarp. Pretty sure there is movement in the rad. Have not drilled a hole in the Thermostat yet. Fan is blowing thru Rad. toward engine will take a picture of the setup today and post this evening.
 

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redsqwrl

Bronze Member
GOLD Site Supporter
I have seen gauges read incorrectly, Depending on pressure, boiling over is at different temps.

210 is not hot for an engine working.
 

Tye one on

Member
I had a thread on here somewhere asking the same question regarding my 343 with a 318 overheating. It would read 210-220 under a good load and I was worried that it was to hot. I had several people reply to my post that said that was within range for a 318 and I should just get a higher pressure cap and run it. I put new cap on and ran it that way for years with no boil over. I definitely think the heat gun will tell the real story of what is going on with it.


Sent from my iPhone using Tapatalk Pro
 

PJL

Well-known member
Ignition timing will make it run hotter if it not right. Carb mixture too lean will run hot.

If it was my cat I'd pull the radiator and have it gone through if it's never been done.
 

tucker mule

New member
Ignition timing will make it run hotter if it not right. Carb mixture too lean will run hot.

If it was my cat I'd pull the radiator and have it gone through if it's never been done.

If its a rebuild - was the temp sending unit changed ?? May not be correct for gauge.......Like stated before - Temp gun is the tattle tale - cheap and good investment.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Some thoughts:

Generally speaking, the stock Tucker cooling system works well and cools the engine without issue, even when the engine has to work hard. Is the electric fan in addition to, or in place of, the stock mechanical fan? If you are using a mechanical fan, is the blade the original one?

The 210º temperature really isn't that high.

What concentration of anti-freeze to water are you using. While anti-freeze increases the boiling temperature of the coolant, it isn't as efficient as straight water in giving up heat. A 50-50 mix is generally considered to be the right mixture as long as that meets your freeze protection needs.

Depending on the thoroughness and detail of the rebuild, it's not unusual for a rebuilt engine which has tight clearances to run somewhat hotter initially until the engine has been broken in.

Measure the radiator inlet temperature (top hose) and the radiator outlet temperature (lower hose) and compare the numbers. That difference tells you how effective the radiator's cooling is. I think you should see at least a 20º drop.

I bought one of the laser heat guns mentioned above and found its readings to be of questionable accuracy. Moving the laser spot only 1/4" could give a reading many degrees different... to the point it wasn't believable. I then purchased a digital thermocouple thermometer (https://www.amazon.com/gp/product/B018QHQSB8/ref=ppx_yo_dt_b_asin_title_o04__o00_s00?ie=UTF8&psc=1)

I found it much more accurate, and with two leads I could compare the radiator inlet and outlet temperatures simultaneously.

Very nice looking Tucker! The mirrors are interesting. Can you tell me what they are/where they came from?
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
I had this problem with my jeep I even replaced the radiator. at the end of the day it was the electric fan I stuck the belt drive one back on and cured the problem. that said also when the engine is warm not hot look for little bubbles in the radiator you could have a head gasket leak or the rebuilder might have missed a cracked head.
 

Cidertom

Chionophile
GOLD Site Supporter
One more item to check: Actually feel for air flow. in modifications etc: is there a change that restricted the OUTflow. You should have just as much open area out as radiator area in. Some of the rigs I've seen had very little in the way of outflow due to extra shields and plumbing. One way to check would be block the hood open with a 2x4 and bungee it down to keep in place. Take a drive if it keeps its cool then you have a flow issue.
 

Cltjones

Member
Thanks for all you comments. Will definitely check them all. Do not have a mechanical fan installed what size should i have the Rad is 2'x2'x4". Looks like it is weeping from the top seam of the rad. If using a thermal gun what would the temp be on top of the engine 265F? Top rad hose around 190F- Bottom rad hose 175F. Mirrors are off a Bus. Electric Fan has been removed and am going to purchase a mechanical fan. Shroud on the Electric fan covered 1/3rd of the Radiator. It was also mounted in front of the Rad. blowing air thru the radiator toward the engine.
 

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Blackfoot Tucker

Well-known member
GOLD Site Supporter
The electric fans I'm aware of are more efficient as pullers than as pushers. If the electric fan's shroud only covered 1/3 of the radiator it didn't have a chance... My snowcat buddy and I installed a Griffin Thermal Products "Universal Combo" which had two fans with one shroud and would allegedly cool 550 HP. Except it didn't cool a whole lot less than that in a snowcat application! We replaced the totally misrepresented Griffin product with the largest radiator we could fit from Ron Davis Racing Products. It also has two fans and the shroud fits tightly. Great craftsmanship and the best thing is that it does the job! Both of those setups used the fans as pullers.

Either way though, they aren't nearly as effective as a mechanical fan with a shroud. I think you'll find when you go back to the stock setup your cooling problems will be over.

A radiator cap allows the cooling system to pressurize, and that increased pressure allows higher temperatures before the system boils. If your existing radiator is "weeping", that likely indicates it can't handle the system pressure. You should take the radiator to a shop and have them check it out. In addition to the weeping you may find the tubes need to be cleaned out; a process called "rodding".

Good Luck, and thanks for the mirror info.
 

redsqwrl

Bronze Member
GOLD Site Supporter
given your temp data, your problem is the electric fan.

They add load to the engine via the alternator, they are not usually very effective on three or higher core radiators.

stay the course you are on the right track.
 

TalleyHo

Active member
GOLD Site Supporter
I have heard the same thing about electric fans not working on 4 core radiators. Just not enough flow.
 

Cltjones

Member
Hi Looks like we almost have it figured. Put in 7 blade Mechanical fan dropped the temp to 180F. One problem is under the Carb still at 360F. Restricted exhaust flow. Not much room to change things any ideas? attached is a photo
 

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TalleyHo

Active member
GOLD Site Supporter
No Bueno!

I have a similar machine. My exhaust goes down and out through a cutout in the "frame cover" panel. Maybe get the exhaust routed correctly then reroute hydraulic lines... That dead head of the exhaust looks like all kinds of scary to me.
 

TalleyHo

Active member
GOLD Site Supporter
Here you go. Machine just happens to be right outside at the moment. I've got a pretty tight sweep on passenger side as well... As you can see I got away from the glass packs up the front of the cab and went to a single exhaust out the back.

Hope this helps.
 

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Blackfoot Tucker

Well-known member
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That dead head of the exhaust looks like all kinds of scary to me.

I agree with the comment about the exhaust system. I can't believe someone would have a hard 90º bend, let alone right after the exhaust manifold. That would both rob power from the engine and cause the pipe to run hotter. The exhaust pipe being in such close proximity to the oil filter is also a poor design...needlessly heating the oil, which adds heat to the engine and reduces the oils lubricity.

While there isn't gobs of room to work with, you can definitely improve on that system as suggested. For example, the rear cover on the hydraulic pump is held in place with four bolts, and one can re-index that rear cover so the fittings (which can also be changed) better align with where you want the hoses to run.

A competent exhaust shop should be able to do a much better job. Perhaps bring the machine to such a place and discuss both exhaust and hydraulic component re-positioning?

I know a fair number of Tuckers have dual exhaust systems, and if that's your preference, that's fine. Running a single exhaust smooths out the exhaust pressure pulses from the respective cylinder heads and reduces the blatting sound common to dual systems. That said though, it's considerably more difficult to build such a system with the engine installed and working in such tight confines. I can highly recommend a guy in SLC, but that probably won't help you...
 
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