Running hot: Denso radiator problems? Next best alternative?

[B.E. Coyote]

W

I would say say swap it out if you've had cooler temps prior. I am working on my engine rebuild and am getting rid of my Denso in the process. Ran hotter (10-20) than any other radiator I have had in it including standard Advance Auto replacements. Sure it works, but hotter consistent temps long term don't help longevity and I believe it may not have caused but did contribute to my current engine situation. Everything was fine until, like you OP, swapped out all the refresh items at the same time.

I have had a lot of good experience with other Denso products is why in part I went with the radiator. I still think they are good, I just won't buy or recommend one of their radiators again.

It has always been in central NC area. Climates shouldn't be part of the discussion though. Who wants to buy a product (other than an emergency patch) that would only work in certain areas or certain times of the year? If I wanted to road trip south or out west I shouldn't have to worry that the parts I am running are not up to the local conditions for basic stuff...like driving.

What are you swapping it with? Im not sure what the temps were before. Jeep is new to me and the coolant was awful and rusty. I was getting some boil over into the resevoir. It was nasty enough that I figured a refresh was in order.

 

[macleanflood]

I was sold on Denso until folks brought up issues. I'm trying a Koyorad. So far so good. Drove all the way to Sand Hollow and back. Highest temps were 93 outside. Lots of high rpm pulls in the sand dunes. Dunno if it's the answer but I'm giving it a shot.


View: https://youtu.be/FFGzGCquRq0?si=lxk7FslURhFcKP-P

-Mac

 

[User4574]

W


What are you swapping it with? Im not sure what the temps were before. Jeep is new to me and the coolant was awful and rusty. I was getting some boil over into the resevoir. It was nasty enough that I figured a refresh was in order.

I have a Koyo new in box I bought on a sale. On the fence about a CSF but don't know if I'll go there or not. Honestly other than the inconvenience when they blow out they aren't hard to swap so I will probably go with the Koyo and see and if not try another. Denso will get flushed, plugged and on the shelf as an emergency backup for now.

 

[rweathers2001]

I had the same issue a few years ago with the Denso radiator. On the highway it would run over 210 on the gauge. I changed it out for a Nissen radiator and a Robert Shaw thermostat and have had no issue since. It stays right below 210 on the gauge now no matter what.

 

[Harold&Cat]

I just did a complete swap of the cooling system on my new to me jeep and it is running really hot. 2003 4.0 auto 103k

Mopar wp, denso radiator, gates hoses, belts and new tensioner and idler. Hayden HD fan clutch

Burped completely, zerex o5. did a pressure test and a block test.

Currently doing a 2nd flush with thermocure and considering swapping out the brand new denso radiator for something different. I have read a few instances of others having a similiar experience.

It will idle at 212 per the torque app with the heat on but climbs up to 230 with the AC on, maybe higher but I don't let it. This is in temps in the high 70's low 80's.
Same temps with the thermostat pulled.

Any suggestions

Have you checked the thermostat ? The 195 Robert Shaw high flow thermostat is highly recommended .

I installed a Hayden 2771 fan clutch in March along with a Flowkooler water pump . I honestly can't hear much difference in noise . I let it idle for over 30 minutes sitting in the sun with 91 degree outdoor temperature with the AC on . The temp gauge stayed just below the 210 mark and the AC was blowing cold . We took it for a short trail ride and the temp stayed the same and the AC was nice and cold . It actually runs cooler sitting still or putting down the trail than at highway speed. Highway speeds it runs 210 or just to the right of 210 but still touching it . Air conditioner blows nice and cold at all times .
I would say this combo is a win , only time will tell about durability .
Koyorad A2102 radiator
Hayden 2771 fan clutch
Flowkooler water pump
Robert Shaw 195 thermostat

 

[B.E. Coyote]

Thanks, currently doing a thermocure treatment and I dont see a change even running no thermostat. Admittedly , it is water and not 50/50 coolant.

Im going to assume the wp is good. Brand new mopar, not leaking and I know it is moving water.

I did order a CSF oem type replacement radiator and a gates thermostat to try.

I have a new Hayden hd fan clutch on it but Im suspect of it. It doesn't roar like people complain about and doesn't seem to spin all that fast or increase in speed after it is hot.

 

[KennethS]

Thanks, currently doing a thermocure treatment and I dont see a change even running no thermostat. Admittedly , it is water and not 50/50 coolant.

With no thermostat it should run a lot cooler. Just for a data point, after a water pump replacement I ran mine with no thermostat to ensure no leaks and the temp gauge stayed a bit below the tick mark between 100 and 210.

And FYI, straight water will cool better than 50/50 mix, but the straight water will allow massive rust and corrosion.

 

[B.E. Coyote]

I have a Koyo new in box I bought on a sale. On the fence about a CSF but don't know if I'll go there or not. Honestly other than the inconvenience when they blow out they aren't hard to swap so I will probably go with the Koyo and see and if not try another. Denso will get flushed, plugged and on the shelf as an emergency backup for now.

What did you end up using? Did it also stay 10-20 below the denso?

 

[B.E. Coyote]

Fan clutch made a big difference but still having issues, swapping out the Denso this week for the CSF 3244

 

[B.E. Coyote]

Got rid of the Denso today and I am thrilled.

Yesterday I used the Denso to do one last flush, all water and a bottle of thermocure. Drove it for 2 hours.

Flushed it well 3x with distilled and installed the CSF, 3 heat cycles of burping it, and then filled with zerex shooting for a 50/50 mix.

Long test drive

Yesterday was 87 with all water

Today 92 degrees and 50/50. Driving I was at least 10 degrees cooler at all times. Average moving range was between 206 and 215 with AC. It would creep a little higher at lights but go back down quickly/

I also noticed the temp would rise slower and drop faster.

My only concern was when I came home the temp was about 215 when I pulled in the driveway. I sat for with it idling and full AC and it was slowly climbing. Got to 227 before I drove it around the block once with the AC off to get it to 210 before shutting it down.

I bought this in October and have worked on it until now. Probably driven it less than 200 miles and that was mostly test drives and thermocure flushes. I finally feel like I am safe to go enjoy it a little.

 

[Bad Larry]

I’m running a Denso with a UMW-22160 clutch in South Texas and haven’t had any issues. It always sits right below the 210 mark.

I wonder if there is a QC issue going on with Denso. Will have to keep an eye on mine

 

[B.E. Coyote]

I’m running a Denso with a UMW-22160 clutch in South Texas and haven’t had any issues. It always sits right below the 210 mark.

I wonder if there is a QC issue going on with Denso. Will have to keep an eye on mine

I did a complete restoration of the system after buying this in October. The coolant was disgusting. After all the new parts and coolant flushes, I started having problems as soon as we started having warmer weather. I never suspected the radiator until I came across this thread.
https://wranglertjforum.com/threads/denso-radiator-marginal-in-hotter-climates.89550/

Then I found others with the same bad experience even though many if not most Denso reports were positive.

The stock radiator has 55 tubes, the Denso has 47 and the CSF has 58. I know there is more to cooling than just tube count, but that and the bad reports from others made me think it was worth the try.

 

[SRCustom]

I was sold on Denso until folks brought up issues. I'm trying a Koyorad. So far so good. Drove all the way to Sand Hollow and back. Highest temps were 93 outside. Lots of high rpm pulls in the sand dunes. Dunno if it's the answer but I'm giving it a shot.
-Mac

One thing I never see mentioned in discussions about radiators here is the core thickness/number of core rows. I'm in the process of replacing my radiator, and this is what I've noticed: While the Denso may (or may not) be the best quality, the cooling capacity is marginal at best. The Densos I see listed have the thinnest cores.