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If that's a picture of your radiator, then I'd lean towards the "too much radiator" answer. Seems to be a 4-row or equivalent.. Also looks like you might have a mechanical fan.

One way to check is to block off some of the radiator (there appears to be ample room between your intercooler and the radiator to slip some cardboard in front of it). If it gets better, then you likely have too much radiator, or too much airflow through the radiator.

If you have a mechanical fan, it should have a clutch on it. If it's direct drive, I'll guarantee you'll be moving too much air in most situations. Electric seems to be quite popular with these, as they don't really require all that much cooling.
 

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Jon

Do you have a shut off valve in one of the lines going to your heater? When the heater is properly plumbed in the path of the coolant some of the coolant will bypass the thermostat and cause the engine to run at a lower temperature along with a larger coolant temperature fluctuation if there is not a shut off valve in the heater coolant circuit. Do you have your temperature sensor located in the front of the cylinder head just before the thermostat?
 

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Isn't some sort of bypass *required* in a cooling system? That was what i was taught.

Now, where that bypass dumps / the route it takes might make some difference:

On my Chevy, bypass is through the heater core only, and a hose goes from the intake, to the heater core, then to the radiator on the same tank as the lower radiator hose, only at the top. You shut off all flow through that heater core and bad things are a gonna happen.. Air temp is controlled by air doors in the heater box.

This is probably not optimal plumbing for quick warm-up, as it means the bypass coolant that normally should stay in the engine and heater core is getting to intermix significantly with the bulk coolant sitting in the radiator way before the thermostat opens. But, it may pay off by including the transmission cooler built into the radiator as part of the bypass loop. Dunno.. It would tend to smooth out temperature swings due to thermostat opening / closing a bit.

Older Chevys returned coolant to a nipple on or very close to the water pump intake. This would have much less intermix with the coolant in the radiator, which means faster warmup.

Other vehicles have dedicated bypass loops, or have a two-way heater control valve that shunts coolant flow to a bypass loop when you shut off coolant flow through the heater core.
 

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I had the same problem in my 96. I ended up pulling the return heater line out of the rad and placing it in the lower water inlet. This helped a lot. I could get 175 out of the engine running the stock 6.5 diesel rad.
 

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Could it be as easy as a stat stuck open? Had a piece of trash stuck once that kept it from closing... Just an idea.
 

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I use a 195 Tstat but if you're not hitting 180 then it makes no difference.

Ditch the fan and grab an electric run on a relay to only turn on when you hit 190 or so.

I haven't turned my fan on in 3 months since it doesn't overheat. It helps save some power being robbed off fan pulley.
 

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Correct me if I'm wrong, but is there really a problem with the 4BT running at 165 instead of 195? I thought that (to a certain extent) an engine that ran cooler than one at "normal" tempature would suffer no ill effects.


Pantherman
 

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Most engines are designed so that they are at their "correct" dimensions only once they reach full operating temperature. Too cool and you can be looking at excess wear, blowby, and such.

Also, you really need your engine oil to get to over 160 or so so that any moisture, etc in it can flash off. (Ditto for trans oil, but not of concern with this problem..) It also will not be the right viscosity per engine design if it doesn't get to the full temp.

And the final problem is that you'll be building carbon in the cylinder, getting poor fuel economy, and all that goes with it.
 

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On my Chevy, bypass is through the heater core only, and a hose goes from the intake, to the heater core, then to the radiator on the same tank as the lower radiator hose, only at the top. You shut off all flow through that heater core and bad things are a gonna happen.
If you shut off flow through the heater core, what bad thing will happen? The outlet on the intake that directs the hot water to the core is in the same portion of the intake as the outlet to the radiator on a small block Chevy. If you block flow through the hose to the core the water will instead be pumped straight out to the radiator via the top hose after the thermostat opens.
 

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"Correct me if I'm wrong, but is there really a problem with the 4BT running at 165 instead of 195"

That's a good question, and it might defy common sense.

My background is in Mechanical Engineering and one of the subjects I worked on was tribology or bearing wear. In a nutshell, yes, an engine can wear quite quickly if it does not attain proper running temperature. My guess is the best temp to run the 4bt would be about 180deg F, with a narrow margin of about 10 degrees.

One element that we found to increase the bearing life was Ph. An acidic lubricating medium almost eliminated wear!!! Problem was the detrimental
effects of acidic solutions on other parts. Ceramic engine parts were under scrutiny at that time to counter this. (Car manufacturers can design/build engines to last much longer than they do but this would counter the "fashion" aspect of the entire package: and engines would outlive the rest of the stuff).
 

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I use a 195 Tstat but if you're not hitting 180 then it makes no difference.
Aren't the Tstat's on our engines different than the typical gasser Tstat? I was pretty sure i read somewhere that it isn't just open or closed, it opens incrementally as the engine warms up and this was why they were slow to warm up sometimes?

Mine runs pretty cold as well, but my gauge doesn't have numbers :rolleyes: workin on a good gauge but haven't gotten there.
 

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If you shut off flow through the heater core, what bad thing will happen? The outlet on the intake that directs the hot water to the core is in the same portion of the intake as the outlet to the radiator on a small block Chevy. If you block flow through the hose to the core the water will instead be pumped straight out to the radiator via the top hose after the thermostat opens.
The Chevy system uses the heater core as the bypass path (I think it's called a "full flow" heater core). Other manufacturers do it, as well. Cut the flow through there and you have no bypass flow.

No bypass means that coolant cannot effectively circulate in the engine before the thermostat opens.. Which in turn means that the heated water can't move to reach the thermostat to open it or will be seriously delayed in reaching it, and then you have formation of hot spots in the engine. Also can cause pressure in the system between the pump and the thermostat to go way up. Depending on which exact engine you're doing this to, what happens next ranges from blown head gaskets and cracked heads to wiped out cylinder bores..

You can bypass the core if needs be (if you were driving on Broadway in Knoxville yesterday afternoon, you would have witnessed a "in the parking lot" bypass operation, as that's how I got home), but you still must have some loop to allow the flow. Which is why I don't leave home without a 3/4" to 5/8" hose adapter in the toolbox. (OT: Does ANYONE make a heater core for 90 Chevy that lasts more than 2 years?? Original equipment one went 13 before it needed replacement..)
 

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Discussion Starter #18
The Chevy system uses the heater core as the bypass path (I think it's called a "full flow" heater core). Other manufacturers do it, as well. Cut the flow through there and you have no bypass flow.

No bypass means that coolant cannot effectively circulate in the engine before the thermostat opens.. Which in turn means that the heated water can't move to reach the thermostat to open it or will be seriously delayed in reaching it, and then you have formation of hot spots in the engine. Also can cause pressure in the system between the pump and the thermostat to go way up.
What about drilling a small hole in the thermostat flange to allow a small amount to circulate?
Does anyone have the part number for the 195deg thermostat? The kids at the NAPA by us, doubt it's existance!
 

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Just some passing thoughts, is your front of the cylinder head higher than the radiator? If you take the radiator cap off are you seeing any circulation? Any possibility of an air lock where the temp gauge is in an air pocket instead of liquid? Can you loosen the plug near the temp gauge to see if fluid is against the thermostat?

Also, are you using a Cummins thermostat? I remember we covered this previously on the Yahoo side:
http://autos.groups.yahoo.com/group/cummins4BT/message/4029

From there:

Re: thermostat


> Terry, my 4bta is running a regular old GM thermostadt along with
> the rubber seal.
> Carl
>
Carl,

You really should try get the proper thermostat. The Cummins design
has TWO sealing areas: one to the water outlet to the radiator, and
one to the internal bypass in the front of the cylinder head. The GM
one only closes to the radiator there by permitting a constant bypass
condition through the cylinder head. I don't know if this would cause
any problems other than causing excessive warm up time situations.

Bob
 

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What about drilling a small hole in the thermostat flange to allow a small amount to circulate?
If you put the hole where I think you're meaning (in the flange that surrounds the center opening of the thermostat) and make it big enough to flow enough to not have the hot spot / pressure problem, then you're back to the overcooling situation again, as you'd be defeating the thermostat's ability to block off the flow through the radiator. Note that most thermostats will have a SMALL hole in the flange to allow air to purge from behind the t-stat.

Bypass flow needs to be from the "engine" side of the thermostat to the suction / intake of the water pump w/o going through radiator.
 
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