Oversized Radiator/Hood Augmentation

[YoungSage]

Hello Team!

 

My 88 Sunrader has just returned from the shop with a newly machined head, newly machined exhaust manifold, new head gasket, valve cover gasket, timing chain, new timing chain guides, new water pump, new hoses, and a new radiator. As I believe the overheating problem was caused by a faulty and too small radiator I am considering replacing the new radiator (which is not oversized but a regular sized plastic version) with a larger, ideally metal radiator which will sit too high for the hood to close and latch due to structural metal supports beneath the engine bay. 

 

Has anyone out there put an oversized radiator in their rig and modified their hood (ie cut a hole in it or put an air scoop in it) to fit a larger radiator? Does this sound like a good or bad idea? 

 

Having had all of this work done to rebuild the cooling system I would like to see the engine running cooler that it currently is. Thanks in advance for any wisdom you may have to share. 

[extech]

what temp is it running at?   should be over 180 or you lose performance and longevity

[extech]

also did you replace the fan clutch?

[fred heath]

Aftermarket electric cooling fan might help. Will pull more air consistently than a fan clutch setup.

 

Cutting the hood would be a bad idea.

You might want to sell in the future. That would be a deal breaker for me.

[YoungSage]

Thank you for the feedback!

 

I had the stock heat gage replaced with an analogue one. The day I picked it up and drove it home, the temperature on a 75 degree sunny afternoon going 60 mph on a flat section of interstate was about 240/50 as I recall. My mechanic said I should pull over and let it cool down if it got to 280. It never did. I have yet to take it up the grade south of town to see how it does with a hill. 

 

I replaced the fan clutch last year with an electric cooling fan. 

 

I am more concerned about damaging the engine again through it chronically running too hot than about resale value. I think it could be possible to create an aesthetic air scoop/ bump in the hood to accommodate a larger radiator which might even increase its appeal. But that’s just like, my opinion - to quote Jeff Lebowski. 

 

Thanks again for your thoughts and wisdom. You people amaze me. 

[extech]

it should not run that hot.  i would be checking timing and check for excessive exhaust back pressure  

[Scott iv]

I installed a 4 row aftermarket aluminum radiator that does not have the ports for transmission cooling. I added a separate transmission cooler. The aluminum radiator is thicker than the stock metal and holds more coolant. The trade off is the thing is delicate and you have to be very careful when working near it or you are flattening fins. My main problems with overheating were a bad clutch on my fan, and exhaust leaking into the motor from a bad head gasket (coolant eventually as well). I feel my decision to replace the radiator was not necessary as many folks here use the stock metal one without over heating issues. 

 

Sounds like you had a lot of work done. Kits for checking if exhaust is getting into your cooling system are cheap and easy to test. Perhaps head bolts were not torqued sufficiently. Electric fan system may need to be evaluated further also. 

[Scott iv]

Couple additional considerations: condition of the fan shroud, and ensuring air is out of your cooling system (burping). 

[YoungSage]

Thank you Scott iv , Extech, and Fred Heath! I am bringing her into the shop today to get a new cap and rotor put on and I will ask about the timing (though I imagine that was set when he replaced the timing chain and guides) and also about checking for excessive exhaust back pressure. I may also take it for a spin up the grade and see what happens with more of a challenge. 

 

Again, thanks so much for taking the time to share your thoughts here. I really appreciate it. 

 

 

[extech]

they likely checked base timing after assembly. your problem may be in mechanical advance or vacuum advance or a combination of the 2

[YoungSage]

Thanks! I’ll check into that. 

[thewanderlustking]

Mechanic here.  Be careful how you approach this and "pre-diagnose" it.  You spent a small fortune having the shop do a head job (and more) for you.  Honestly, it is their responsibility to do that diagnostics and then to MAKE SURE the system is now functioning correctly.   If you go in there with the mentality of "it is this" you inadvertently write them a blank check with no guarantee of it solving the problem.  I have an awesome boss and an equally amazing service writer.  Usually they ask customers the right questions and prevent this.  But as honest and as much of straight shooters as we all are, if I am replacing a radiator (or anything else) and don't see a reason why and I ask "Why are we doing this, it isn't leaking?" and the response is "This is what the customer asked for, give them what they want." I am no longer worried about actual diagnosing the issue.  At this point I have no responsibility to do more than make sure the job I did, is done to its best.  

 

Anyways,, I am not saying you are doing this.  I just see this pretty often where people come into the shop after having done a lot of internet/forum diagnostics and have preconceived ideas of what the problem is and waste lots of money and time throwing parts at it instead of letting the shop do a proper diagnostic job.  And I also know there are a LOT of shops I wouldn't let diagnose a stuck thermostat either...  

 

With that disclaimer out of the way, here is where I would start as a mechanic.  I would verify there is an actual overheating problem first.  I would check the temperature right at the sensor with a laser thermometer and verify the new gauge is reading correctly.  Do this at a couple points as it heats up.  As it gets hotter, a bad sensor frequently has more drift from the actual temp point.  I had a customer come in last week with their jeep claiming it was overheating, and it was actually fine, but had a bad sensor.  At 120, the actual temp and the reading in the scan tool were identical.  As it got to 190, the temp in the ecu was actually reading 215.  When it hit 200, the temp the ecu was seeing was 250!  And the fan of course was screaming.  Obviously this is a slightly different scenario than yours, but the general concept is the same.  

 

Verify the concern, then systematically check and see what is actually causing the concern.  In your case I would be checking the basics, thermostat working?  Fan working effectively?  Look at the radiator with a thermal camera for hotspots and flow.  Verify the last job done, is there air in the system?  Water pump correctly installed?  Timing?  

 

Unless your mechanic already knows there is an issue with the gauge...  280 is an INSANE amount of heat.  I would be concerned as soon as it went to 220-230.  An efficient cooling system on an older vehicle really should operate closer to 200-220.      

 

BTW, internet and forum hunting/diagnoxtics is still extremely valuable tool.  I am NOT knocking that.  Heck, I do it also when I see something out of the norm to at least give me a direction to start in.  Just realize that a GOOD shop should be doing proper diagnostics themselves.  And If I had your truck at my shop, it would have been test driven and verified after the job was done.  It probably would have sat idling for 2-3hrs first, and then been driven at least 10-15 miles.        

        

Edited November 2 by thewanderlustking

[YoungSage]

Thank you Wanderlustking. Great points. I will ascertain if the engine is actually overheating. Time to get a laser thermometer. 

[RaderDog]

I have read all posts. Totally understand what thewanderlustking is saying. 

 

Hoping I can get in on this discussion since it was a post I was going to create anyway. I am about to have my Timing Chain and Guides replaced. While we are in there the mechanic will do the oil pump, water pump, new timing cover, valve cover gasket and tune up(cap, rotor, plugs and wires). He has asked me if I want to put in a new radiator. I understand since he will be already in there. My SunRader runs fine has plenty of power & good gas mileage. I am having him do this because I am leaking oil. Engine is a 1986 22REC with 85,000 miles on it. I have no cooling issues if anything it may run a little cool. About 1/3 instead of 1/2 on the temp gauge(factory on the original dash). I do not loose any coolant and it is clean. Looks like you just filled it with new coolant. Has anyone had a radiator fail? Any suggestions on brand or brass/copper vs aluminum? I appreciate any help in advance. 

 

[extech]

if your cooling system has been properly maintained there is no reason to replace your radiator. regular flushing and coolant replacement will keep the system up to spec indefinitely

[extech]

make sure to get the valves adjusted

[RaderDog]

That's what I thought. I will replace all the hoses while we are in there. I think a valve adjustment is a definite add to the list. Any other advice is appreciated. Thanks.

[extech]

clean the throttle plate and adjust the throttle position sensor

[IdahoDoug]

Former vehicle planner for GM and Lexus here.  I suspect your problem is with switching to the electric cooling fan.  Too many folks research on the net and find themselves being told "electric fans are awesome" by some 18 year old who did it on his Honda Civic and thinks everyone should. Aftermarket electric fans and the motors that drive them usually/often have less max cooling capacity than the powerful engine driven fan that was replaced.  I have over 12k posts on one forum, 3k on several and have seen this internet phenomenon across the nearly 10 makes I currently own and play with.  Your engine and its cooling system were designed to work together by one of the finest engineering teams in the world, and the Toyota truck is known as the gold standard in harsh desert environments the world over - particularly 3rd world environments where they are grossly overloaded, and there is no such thing as maintenance.  Those folks just fix them when they break.  So your cooling system is easily up to the task.  Put the original fan back on it, with a new thermostatic hub (these age and loose effectiveness), confirm the sensor is not the issue (good advice above), be sure the radiator shroud is on it, and drive the wheels off it.  This applies to anyone here with a stock Toyota Sunrader engine.  Be advised, there are more powerful fan hubs likely available for your truck as Toyota made a variety of these hubs to account for extreme applications such as a 1 ton diesel sold into Africa.  Both of my LandCruisers got the blue hubs (less slippage, more forceful cooling) decades ago when I learned of them, for instance.  Best!

 

PS - I acknowledge you had some kind of overheat issue that caused you to have all that mechanical work done and I'm skipping over it not out of disrespect, but because the amount of work you had/are having done would have corrected the damage, and now having a functional factory fan/fresh hub with a new radiator and you should be ready to go.  One comment  I allude to above.  Do you have the radiator shroud in place?  Often, a prior owner will damage it, or accidentally leave it off and then choose not to disassemble everything to put it on.  This part is CRITICAL and often missing on vehicles this age.  Is yours on?

Edited November 4 by IdahoDoug

[WME]

2x Yes, on fan shroud and factory fan and clutch. 

I pulled a 5x8 cargo trailer over 10,000ft passes in 95 degree weather, running the A/C with the factory cooling setup

If you must use an electric fan, use it as an aux pusher in front of the radiator.