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The thermostat determines the minimum operating temp of the engine. The fan/clutch determines the maximum operating temp of the engine. The radiator is merely a passive participant. Since a properly functioning OEM system can keep the engine at 190-220 degrees easily on its own, there is no room for improvement unless some part in the system is failing in which case only repair or replacement of the faulty part is necessary, not aftermarket upgrade.
Thanks. The system as designed discussion is an awesome and robust conversation. It takes skill to simplify it. Starting with the assumption that the system should function is a good starting point for trouble shooting a malfunction. Internal combustion drawbacks aside, always wondered if the heat soak issue wasn't muddied by Bandaid fixes.
The thermostat determines the minimum operating temp of the engine. The fan/clutch determines the maximum operating temp of the engine. The radiator is merely a passive participant. Since a properly functioning OEM system can keep the engine at 190-220 degrees easily on its own, there is no room for improvement unless some part in the system is failing in which case only repair or replacement of the faulty part is necessary, not aftermarket upgrade.
I'm in full agreement an XJ unless it's highly modified needs only an OEM style radiator to cool properly. I off road mine in the summer in the Ozark mountains most of the time on tough trails with the AC on and a stock AutoZone radiator <$100 lifetime in store warranty. It has never over heated where anti freeze was lost and as soon as the electric fan kicked in it cooled back to normal in short order.
If I wanted to improve heat management, the first thing I'd do is put a heat shield between the intake manifold and header. The second thing I would do would be some form of venting.
Actually, I'd do venting first, but to answer your question, no, there isn't a product made. Why should there be? It's just a matter of fitting a sheet of aluminum under the intake manifold. If there was a product sold, it would be overpriced and still be 99% of the work involved it doing one yourself.
Venting doesn't do anything effective. Letting hot air out of your engine compartment doesn't cool down the internal temperatures of the fluids in your engine block and cooling system, which are battling with constant micro-explosions at the core of the engine. That is why the point of the radiator is to extract these hot fluids from the block and force air through them externally. Venting is just an aesthetic and will mess up the air-flow designed by the cooling system engineers.
Last edited by thatXJguy; Feb 19, 2017 at 01:16 PM.
Venting doesn't do anything effective. Letting hot air out of your engine compartment doesn't cool down the internal temperatures of the fluids in your engine block and cooling system, which are battling with constant micro-explosions at the core of the engine. That is why the point of the radiator is to extract these hot fluids from the block and force air through them externally. Venting is just an aesthetic and will mess up the air-flow designed by the cooling system engineers.
The OEM cooling system handles all of that just fine. Most of the time, cooling problems on 4.0's with healthy cooling systems stem from ambient heat accumulation and heat soak especially at low speeds.
I don't have vents because I don't crawl around and/or idle a lot. I also don't have cooling problems. I ALSO don't have any aftermarket cooling "upgrades."
Last edited by mschi772; Feb 19, 2017 at 04:06 PM.
I guess I should clarify that my comment about shielding and venting was for anyone who happens to be in that 0.5% of XJ guys whose cooling system isn't cutting it. Usually it's slow-movers who just get too warm under the hood.
I suppose there's the 0.1% of guys who have a 4.0 (or 4.X) that is so hot-rodded that it actually IS producing more heat than the OEM system can dissipate, but I'd hope they are knowledgeable, skilled, and/or wealthy enough to know what to do about that.
Is that heat shield a product that exists? I don't think I've seen that before.
There is a heat shield that goes on top of the intake manifold to help prevent the heat soak issue that vaporizes fuel in the injectors and causes hard starts. It doesn't do anything to reduce engine temperatures. It's a different solution for a different problem. If you don't have a problem with difficult hot starts, you don't need it.
Some people have also put aftermarket heat reflective material between the exhaust manifold and intake manifold. But again, that may help with heat soak, but it won't do anything for engine temp.
Last edited by extrashaky; Feb 19, 2017 at 11:39 PM.
There is a heat shield that goes on top of the intake manifold to help prevent the heat soak issue that vaporizes fuel in the injectors and causes hard starts. It doesn't do anything to reduce engine temperatures. It's a different solution for a different problem. If you don't have a problem with difficult hot starts, you don't need it.
Some people have also put aftermarket heat reflective material between the exhaust manifold and intake manifold. But again, that may help with heat soak, but it won't do anything for engine temp.
You have a link where to purchase? I've seen it before and wouldn't mind installing it.
Getting back on topic, I've been researching this quite a bit recently as I'm also in the market for a radiator. The popular aftermarket units are the CSF and Champion aluminum units. Two or three row doesn't seem to make a difference. I'd prefer two row for the sake of it fitting well. The issue is both of these radiators have a ton of reviews saying they started leaking within a few years of being installed. Also, the Champions require some slight modifications to work. I think somebody eluded to "martinbuilt's" youtube video comparing the two but they got the manufacturers mixed up. I looked long and hard into an all aluminum two row radiator made by FF Dynamics. I searched every forum I could to read every possible review and talked with one person who had it for several years. From what I gathered it is a higher quality product than both the CSF and Champion and has a lifetime warranty but the company left a bad taste in my mouth. Issues with customer service and whatnot.
All said and done, I will be buying a Spectra OEM replacement from Autozone. I talked myself out of spending the extra $100 on a shiny radiator that I don't need.
I'm new to wheeling, so limited experience. My 90 has the closed loop system with a 5 year old radiator. The trans has a cooler on it. I have been doing a fair amount of wheeling on the beach in the Outer Banks. The sand is very loose and deep in some areas. When I hit the loose stuff the temp climbs up to 210 and the trans jumps to 180 (typically 190 and 150). It makes me nervous, so I pull it off to the side or get out of the loose stuff to cool it down. Is this a situation that would benefit from a larger radiator to handle the spike in heat build up? Or is there an issue with the cooling system? I hope my questions are seen as contributing to the discussion rather than derailing and hijacking.
