Background
GS400
HARD highway miles
Mods, TC, Exhaust, LSD(lower gears), full suspension package.etc...
Maintenance: Religous. Oil change every month. Gear/tranny change every 6 months. All synthetic except for trans which is Toyo Type IV. Steam clean engine one a month,etc.....
Issue:
With A/C engaged, GS would go to RED at low speed in hot climates(above 90). Now this being my 3rd Lexus, I know those needles rarely even budge yet alone go to red. This is unfortunate as a new RM blower is going on shortly.

Tried the usual: Original thermostat tested OK, but I replaced it to be on the safe side and the new one was a improved version that also opened even further. Cost $12.00- Problem still existed
Replaced OEM radiator cap with a new one. Cost $9.50. Problem still existed. Hoses replaced in case lower hose was collapsing. No dice.
Tested Fan switch. Good.
Checked AC pressure: Tested good.
Water pump was replaced when timing belt was done. Everything checked out good.
Ran radiator flush. System was clean. No rust.
Both fans working great, though they stayed on a bit longer than usual at temperatures
Once at speeds over 40mph the system stayed cool. So I decided to pull the radiator since everything pointed to poor efficiency.
Much to my surprise, the one issue I overlooked was a blocked radiator between the condenser and the radiator. Now, I always spray water through the fins of the condenser to clear any debri from the fins. Well, apparently I was pushing all of this junk on the fins of the radiator.
To solve this issue, the radiator can be cleaned while still in the car if you would rather not deal with the trans lines.
I took off the fan shroud (5 minutes). Remove top hose and ECU cooler hose. Removed the top 2 12mm bolts holding radiator to bracket. Pulled radiator forward 6 inches and removed the debri with a shopvac. The debri was packed in there. I then placed a large piece of cardboard between the condenser and radiator . Spray water from the engine side of the radiator to the front to remove the junk. I was amazed at the debri removed as it covered my driveway. See pics.
15 minutes for a really good clean. Be careful as too much pressure will bend the fins.
Final result. Perfection-no overheating whatsoever. The needle never moves and the AC blows even colder than before. So how did it happen. Well the garbage that goes through the condenser cannot be prevented. However I notice that the cheap seal on the top of the radiator and condenser was worn away. This is directly in line with the grill so anything that gets through the grill will easily pass through this space. I replaced all of the original seals with some quality weather stripping.

 

pic2

 

All of the dark spots is dirt packed between the fins.

 

Yow-wee!
That is quite a build-up of stuff..thanks for the tip.

 

I know what you mean about the cheap foam seal. Mine was wearing out also and practically useless. There is also one at the bottom that I saw the other day when flushing my tranny fluid.

I fixed or replaced my top one with something better. I went out an bought a strip of that black rubber scuff board stuff from Home Depot. I think a 6 ft. strip was like $1.50. You know, the type they use as a baseboard around walls in commercial areas.

I measured the width between the radiator and condensor, viewing how it would sit with the lip part resting on the radiator and used a yard stick to make a straight cut. I cut a strip from the side of the scuff board that has the small lip, that lip is the part that goes on the floor.

After carefully cutting it with a box knife, and I'd trimmed it a couple of times after fitting to make it lay on top perfectly, I had to cut sections out to make it fit around the brackets. I then used some J-B Weld expoy (Very heat resistant) to epoxy the lip part to the radiator. I only epoxy'd one side, the lip side and let the opposite side just rest in place on the condensor.

It looks very professional and like it belongs there.

Also, before I did that I also bought some round weather stripping. It comes in different sizes like 3/8, 1/2, 5/8, 3/4, etc. I think I used the 5/8, but I took the round weather strip and pushed it in the crack at the top of the condensor, right under the front engine compartment cross brace. There was another piece of foam in there and I just pulled it out and put the round weather strip in it's place.

You'll see it.

Anyway, the job went smooth and it all looks nice and professional.

 

Wow, so it was a simple solution. I will keep that in mind. Thanks for the tip and your time to take pics.

 

As RA40 said, that is a huge amount of debris, as if you drove through Kansas during harvest season!

How many miles worth of debris is that? And what does your air filter look like?

I wonder what the point of that foam seal is. Is it to channel air through the radiator? This air has already been forced thru the condenser- I don't see why it needs any further help. But maybe it is to keep the debris where you found it, and not dirty up the engine compartment.

 

120,??? miles. Very hard miles. Air filter is cleaned once a month. Like I said, in terms of service, this car is taken care of very nicely which is why the whole radiator issue came as a shock. Though I replaced all of the factory foam with higher quality stuff, the one at top betweek the radiator and condenser appears to be the all important one. But like you said, there is no way to prevent anything from getting through the condenser to the radiator. Especially since the fins on the condenser are larger (more gets through) than the fins on the radiator.

 

Dang dude....do you go off-roading with your GS? LOL!!!

In any case, thanks for the info.

Pete

 

Most of the time when your car runs hot at idle or low speed it is the radiator...........I made a long extension for my vacuum to clean this area and it works well but I did not have as much as you had..........Also be carefull with your coolant to water mixture .........to much coolant will make car run hotter than normal.