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Unread 04-12-2013, 06:52 PM   #1
ForeverNoob
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Troubleshooting another hot 304

Based on the factory gauge, my 304 is running far too hot.

Common causes and my solutions:

Retarded Timing - checked and set at 8* BTDC

Thermostat not opening - replaced with new 180 stat, verified opening using spill proof funnel

Water Pump - replaced with new NAPA unit

Clogged Radiator - Used Prestone Super Flush

Defective Cap - Replaced with new 13lb cap.

I am running a 7 blade belt driven fan with a clutch. The clutch seems to be operating fine (how do you test these? It moves a TON of air). There is also a fan shroud.

When I bought the Jeep a few weeks ago, it was not overheating, but it was also colder out then. Also, the PO removed the thermostat and was running a 9lb cap with no overflow bottle. I am seeing a consistent and steady 19 in Hg at the manifold, so I don't believe there is a head gasket issue. At the time my thermostat opens, the needle on my factory gauge is buried. The ported vac switch for distributor advance changes positions shortly after the stat opens (seems logical). This leaves me with 2 questions:

1. Is there any reason to believe this thing is really overheating based on a 36 year old gauge?

2. Where can I get a cheap mechanical gauge with a 1/8 NPT sensor to fit the (I assume) factory location in the manifold? Everything I've found is either 1/4 NPT or electrical.

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Unread 04-12-2013, 08:19 PM   #2
lucdog
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Does it feel or smell hot? Any pinging on Acceleration?

My DD 7 with a 304, shroud, and a ton of miles on the radiator runs just past center on the '78 factory gauge.
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Unread 04-12-2013, 09:31 PM   #3
ForeverNoob
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No ping at all... it seems to be running cooler now than it was before. Heater hoses and top hoses are hot to the touch, bottom hose is significantly cooler. Seems like I have decent flow. The heater will bring the temp gauge back down in the normal range. On cooler days, before all the work, the needle would run just about center on the gauge. I'd sure like to know for sure where it is before I trust it. I'm thinking the gauge is wrong because the fuel gauge doesn't work correctly either, and I haven't researched it yet, but I know they are tied together somehow. Thinking maybe the PO thought it was running hot and pulled the stat, which brought it down into the mid range on the gauge until the pump went bad on me...
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Unread 04-12-2013, 09:37 PM   #4
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I'd get an accurate gauge on there before assuming that it's running hot. As long as you have the fan and the shroud and no leaks in the system you should be fine.
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Unread 04-12-2013, 09:41 PM   #5
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similar problem, howell, dui,...replaced radiator cured problem
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Unread 04-12-2013, 10:06 PM   #6
ForeverNoob
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Quote:
Originally Posted by Galt View Post
I'd get an accurate gauge on there before assuming that it's running hot. As long as you have the fan and the shroud and no leaks in the system you should be fine.
Quote:
Originally Posted by ForeverNoob View Post

2. Where can I get a cheap mechanical gauge with a 1/8 NPT sensor to fit the (I assume) factory location in the manifold? Everything I've found is either 1/4 NPT or electrical.
I'm with ya... but I'm not sure I want to trust an electrical gauge. Any idea on where to get a mechanical one?
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Unread 04-13-2013, 12:24 AM   #7
82JeepCJ7
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Any autoparts store will have a mechanical temp gauge.
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Unread 04-13-2013, 06:31 AM   #8
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Quote:
Originally Posted by 82JeepCJ7 View Post
Any autoparts store will have a mechanical temp gauge.
And they do... in fact, every parts store in town has at least one. But they all use 1/4 NPT. The tap for the sensor in the manifold is 1/8 NPT...
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Unread 04-13-2013, 08:31 AM   #9
82JeepCJ7
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There should be an assortment of adapters that come with a gauge.



On the 304, there are several locations you can put a mechanical gauge. They have been covered on here a bunch of times, so I will not regurgitate that information, but its very easy to do. On mine I used the port on the thermostat housing. I have both the stock gauge and the aftermarket gauge to cross check each other. 9 times out of 10 the stock gauge reads off and the mechanical confirms I'm at 190

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Unread 04-13-2013, 09:13 AM   #10
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Quote:
Originally Posted by 82JeepCJ7 View Post
There should be an assortment of adapters that come with a gauge.


On the 304, there are several locations you can put a mechanical gauge. They have been covered on here a bunch of times, so I will not regurgitate that information, but its very easy to do. On mine I used the port on the thermostat housing. I have both the stock gauge and the aftermarket gauge to cross check each other. 9 times out of 10 the stock gauge reads off and the mechanical confirms I'm at 190
I haven't seen several locations, I've only seen 2. I'll do a little more looking. I don't want to use the port on the waterneck for 2 reasons: 1, it is post thermostat, and my stat opens after the factory gauge is buried. 2, the waterneck is physically much cooler than the manifold location even after the stat opens. I don't know if this indicates a problem of some sort, or if the waterneck dissipates heat faster. Not being a smartass here, just an honest question: How can you verify that the aftermarket gauge is giving you an accurate reading when the sensor is in the waterneck?

The adapters sold with a mechanical gauge are simply pipe bushings to go from 1/4 NPT (the thread on the nut for the thermocouple) to either 3/8 NPT or 1/2 NPT. The reducer you have pictured won't work. You can't use a bushing to reduce the size of the nut on the thermocouple because the sensor won't fit through a reducer bushing. I could, in theory, use a long pipe nipple or a piece of threaded pipe and a coupler to house the end of the thermocouple, but again, it will dissipate heat and likely give an inaccurate reading.

It's beginning to look like my only option for a sensor before the stat is going to be an electrical gauge...
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Unread 04-13-2013, 11:49 AM   #11
82JeepCJ7
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That section in the thermostat housing is part of the bypass. My mechanical gauge starts to read the increased temp as soon as the water starts to warm up. There is always water flowing though there no matter if the thermostat is open or not.

When I installed my gauge, the capillary tube end fits down into the adapter. The threads on the thermostat housing are much larger than the capillary tube end.

Here is mine. Take my advice or not. But I've actually done this and it works.
img_1589.jpg  
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Unread 04-13-2013, 01:50 PM   #12
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Okay, apparently your water neck is different than mine. I have one threaded port. It is post thermostat and would not supply an accurate reading. The only thing on the bypass side of my water neck is the hose nipple. You are using a bushing to go from a smaller nut (thermocouple side) to a larger hole (water neck side) which works fine. I would have to use a bushing to go from a larger nut (thermocouple side) to a smaller hole, which the thermocouple would not fit through, assuming I used the only other port I have available, which is the factory sensor location in the manifold.

I'm really not trying to be argumentative. I would love to take your advice. But it doesn't work in my application. If I could show you a pic, it would be easier for you to see that...

On the bright side, I did find a list of ohm readings that the factory sensor should read at different temp readings, and I'm pretty sure I'll be able to use that to determine what temp I'm actually running at, assuming my temp sender is not bad. For 6 bucks, I'll probably just go ahead and slap a new one in it...

UPDATE: Checked ohm readings on a new temp sender, and the engine is running exactly where it should be. Looks like a gauge problem. Anyone ever used one of the Omix Ada aftermarket replacement gauge clusters?

Last edited by ForeverNoob; 04-13-2013 at 05:10 PM.. Reason: Update
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Unread 04-15-2013, 03:43 PM   #13
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For lack of having any other available place to thread in a mechanical temp gauge I pulled a steel pipe plug that the P.O. stuck in here (that was a chore, to not gall the threads) and it's been working well.



...and there was juuuust enough room to mount the gauge in my dash here, just to the right of the defrost ducting;

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Unread 04-15-2013, 03:51 PM   #14
82JeepCJ7
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FYI: Any of the threaded ports in the thermostat housing are going to be in the bypass system. The one in the intake will not see adequate flow until the thermostat opens.
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Unread 04-15-2013, 04:13 PM   #15
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Quote:
Originally Posted by ForeverNoob View Post
Okay, apparently your water neck is different than mine. I have one threaded port. It is post thermostat and would not supply an accurate reading.
Umm...isn't the port on the thermostat housing the factory location for the electrical temp sender?

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