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Strange engine overheating...on a V8?


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I thought even though its not jeep I would open up the mechanic side of this to see if anybody had any ideas. The engine that is now in my truck is a good strong running 305 because it is what I found in short order that would have the same motor mounts as a 350 or ls1...anyway. I cannot for the life of me keep it cool. I have a custom, quality aluminum close to stock size radiator and two decent CFM fans that run constantly(was told it kept a hopped up 360 in line). It has an edelbrock carb that I have adjusted jets and rods to try to run richer and leaner to maybe cool it down. I have also tried different timing. It has stock manifolds, pretty much stock 305 I think. Only thing I can think of is maybe it is something internal, that is where my question starts. I have another 305 that I am going to put in and see if it makes a difference. I have heard guys running there v8s on stock jeep radiators. Anyway if anyone has any engine tech I would be interested in it, before I pull the motor or dump the change for a remote radiator setup. Also I have a cowl hood that is open in the back to let alot of heat out.

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A neighbor swapped in a brand new Ford engine into a wrangler last year. He could not keep it from overheating, had a custom radiator made, hood scoop, fan shroud, everything. He finally found out the brand new engine was shot (That's Ford for you) and had to replace it. I can't remember exactly what was wrong with it, but it sounds like a similar issue you're having.

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V8's in XJ/MJ's need special cooling system modifications. heck the freaking things are marginal with a 4.0 and they LIKE it hot. Chebys are cold blooded engines.... NOT the best combination. It can be done, but it also can be quite costly...

 

I have wanted to build a street MJ with a crate 350 2WD for some time.. This "minor" dilemma is my biggest stumbling block...

 

CW

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I have a custom, quality aluminum close to stock size radiator and two decent CFM fans that run constantly(was told it kept a hopped up 360 in line).

 

What fans are you running and what's the actual combined CFM? Most aftermarket fan manufacturers are wildly optimistic on their CFM ratings. Are they both shrouded close to the radiator? I tried several adaptions at first keeping my stroker cool with the two electric fans until I finally found the combination and installation that worked well.

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i'd also like to make sure you're reading the temperature with some sort of accurate gauge. #1 preference being a laser thermometer on the thermostat housing and radiator necks. check to see that you're not being lied to!

 

edit: and one other thing,

when you say "hot" are we talking 220 or are we talking boiling over and blowing radiator caps every-time it runs? how hot is hot?

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My first piece of advice is to not jump to the most expensive, time consuming solution to your issues. Converting to full hydraulic steering to fit a larger radiator? Swapping the engine to fix a cooling problem? Take a deep breath and think this stuff through logically. It is not wise to throw parts at a problem without having a good understanding of what is going on. That is what counter jockeys at chain parts stores do that don't know any better.

 

Now some questions that need to be addressed:

What is the history of this engine?

Did it run fine in the donor vehicle?

How old is it?

Has the cooling system ever been flushed?

Are you running a high flow water pump?

Have you replaced the thermostat?

If yes, what did the cooling passages look like that you could see?

Was there a lot of build up and crap in there?

Was the old coolant rusty?

Is the radiator hose collapsing?

 

As previously mentioned, make sure the gauge is correct and check the temperature with a laser thermometer. Good photos of the engine bay and fan/radiator set up will help too.

 

Willy

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  • 3 weeks later...

The engine swap would be cheap, just time consuming. I have another good running 350 in a grand prix, that I could have out and in the truck in a day. If it is not something internal, then I think my next step is a a remote radiator in the bed. That would probably be my best long term option I would think if I ever wanted to drop a 400 in down the road. I might just throw a lift on the old cherokee and call it quits for awhile on the truck.

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My first piece of advice is to not jump to the most expensive, time consuming solution to your issues. Converting to full hydraulic steering to fit a larger radiator? Swapping the engine to fix a cooling problem? Take a deep breath and think this stuff through logically. It is not wise to throw parts at a problem without having a good understanding of what is going on. That is what counter jockeys at chain parts stores do that don't know any better.

 

Now some questions that need to be addressed:

What is the history of this engine? Don't know picked it up from a friend who got it from a friend

Did it run fine in the donor vehicle? No idea, was told it was fine

How old is it? I'm guessing 80's

Has the cooling system ever been flushed? Yes, plus it has a new custom (close to stock size all aluminum) radiator

Are you running a high flow water pump? Stock waterpump

Have you replaced the thermostat? No thermostat during the summer, I cut the guts out of the old one and just left the ring

If yes, what did the cooling passages look like that you could see?

Was there a lot of build up and crap in there? Not that I noticed

Was the old coolant rusty? No

Is the radiator hose collapsing? No

 

As previously mentioned, make sure the gauge is correct and check the temperature with a laser thermometer. Good photos of the engine bay and fan/radiator set up will help too. I will take some when I get home

 

Willy

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Yeah I have tried it all. More flow less flow. I don't think I have enough radiator but everyone that looks at it seems to think it should do good enough with normal in town driving. I am about at wits end. It sounds great has plenty of extra power I just can't use it for what I want to at the moment.

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This might sound stupid .... But is your thermostate right side up :dunno:

And how long has this motor been in the jeep. I ask because I'm thinking there might be soom kind of blockage in your coolant system.

Just an idea because i know my time is coming with the LS1 running hot too..

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  • 2 weeks later...

I will get some pictures of the current setup, and next time I am around an IR thermometer check the radiator. I have myself pretty much convinced that the end all cure will be to relocate the radiator to the back and get a large enough radiator to not have to worry about it. My biggest issue now is finding someone in my area that can help me do it. I am sure I could figure it out, I just don't want to create a monster that is impossible to bleed properly or indirectly create another problem :doh: .

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I seem to remember reading somewhere that one of the later model Jeeps had a steering gearbox that was positioned differently and allowed more space for a bigger radiator.

Do you have an AC condenser in front of the radiator?

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That's funny. I just want to drive my damn truck out on the trails longer than 20 minutes without shutting down. I have two electric fans with shrouds that move a decent amount of air, I built a cowl hood to let the most heat out as possible. I had a custom aluminum radiator built ( granted it is pretty much the same overall size as stock) I have rejetted my carb, tried different timing settings, checked and rechecked gauges used IR thermometers to double check again. I have tried every coolant additive on the market........anyway you get the point. This truck is going to be over budget before I even get a chance to go out and break something.

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I seem to remember reading somewhere that one of the later model Jeeps had a steering gearbox that was positioned differently and allowed more space for a bigger radiator.

Do you have an AC condenser in front of the radiator?

 

 

No this truck doesn't have an A/C condenser

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If I am going down the road with the thermostat out, It will get back down to around 160, if it sits idling the temp slowly creeps up. I bought a taurus fan in hopes of fitting it in, but it would hit the water pump in any configuration I put it in. I hate to spend big bucks on fans that will still have to run non stop draw tons of amps and still potentially not be enough. If I knew someone with the fans I would try it, but to blindly go out and drop that kind of money it is what was leading me towards the remote radiator.

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If it'll stay cool on the road, then the radiator is theoretically good enough. Sounds to me like you're just not moving enough air with those fans. There are plenty of cars in the junkyards that had pusher fans. I think my fan came from an Aerostar. :dunno: (it's in my hood scoop pulling air out of the engine bay). Should be a relatively inexpensive way to experiment.

 

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