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Cool Lower Radiator Hose Driving Me Mad

foggy agave
Go to solution Solved by TobyB,

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Hi everyone, I'm new to 2002 faq, but have read helpful postings often. Sorry for the long post, Thanks in advance for any help!


I'm worried that the cooling system on my 1971 2002 is not circulating correctly. Spent all weekend wrenching - scratching heads with my local independent garage - even had a phone convo with Thee Mike MIller ("go see Bill Arnold") - now it's toying with my mind!


I noticed a close to red temp gauge while driving a few days ago (normal temp is 1/4 above blue) I touched the lower radiator hose - it was cold - which I thought meant a bad thermostat - so I replaced it.


• Tested new thermostat in hot pan of water (btw - old one works too)

• Flushed the radiator with a hose top and bottom

• Forgot to set heat lever full on until after filling and running engine (me = idiot)

• Burped system by parking on steep street, running engine without cap

• Radiator is a new Silicone Garage 3 core less than 2 years old

• Water pump is less than two years old

• I just rebuilt the top end (those two years ago) so I know what's at stake!


Car drives at normal temp so far today (2 test drives of a several miles each in cool foggy coastal weather.) Big but...


• Lower hose is still cold, so is the bottom of the radiator!!!

• Thermostat, top hoses, top of radiator are hot

• Driving temp is normal - so far! - 1/4 inch above blue


This doesn't seem normal to me - cool lower hose - I seem to remember that all hoses are normally hot after a few minutes of driving. I'm planning to drive from SF to Monterey this weekend for Festorics - hence, the worry.


Do you think I'm dealing with trapped air that isn't allowing thermostat to function correctly?


Or am I just in denial… R-A-D-I-A...


Or - What??


Thanks for any help - otherwise it's off to see Bill in San Rafael!


Mark : )


"One blown head - hoping to keep it that way"


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Lock into the top of your radiator, if you see any rust flakes plugging the tubes, the rad needs to be be rodded. This usually happens when the engine overheats severely and the rust flakes break loose in the engine block.

Edited by allbim

No amount of skill or education will ever replace dumb luck
1971 2002 (much modified rocket),  1987 635CSI (beauty),  

2000 323i,  1996 Silverado Pickup (very useful)

Too many cars.

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Thanks allbim - radiator is new - looked clear - no severe overheat has happened - not even running hot other than the other day. Fluid came out bright green, hose water went right through, came out clear. Can a new radiator go bad in two years? My problem sounds like it's the radiator though, right? All the hoses should be warm or hot under normal running?

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 the only thing which makes "sense" to me is a blocked radiator at the bottom outlet ??


 Did you remove the lower hose, then put the garden hose in the radiator top inlet pipe (leaving the rediator cap in place) and get water coming out of the radiator bottom ??  In other words, verify that you actually have good flow through the radiator from top to bottom ??


 Here's a wild idea:  how about the concept of a small clump of crap in the bottom of the radiator ..... too big to wash through the outlet pipe, thus acting as a "valve" which restricts flow out of the radiator ??

  ---  remove the radiator is the only way to check.


2 years ago I had a heating problem.  Turns out there was quite a bit of "gooey stuff" in the cooling system that washed out of the head and into the radiator.  I just happened to see it on top of the tubes when I removed the radiator cap one day.

     I'm thinking that while the goo was in the head, it was "coagulated" and partially blocking the coolant flow out of the head.  Then it migrated into the radiator and I just got lucky and saw it.  I removed the radiator, turned it upside down, and flushed out quite a bit of the goo.  Don't know what it was.  But the cooling system has remained nice and cool since then. 





Edited by OriginalOwner
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  • Solution

That would be a properly functioning radiator.  And now, a properly functioning thermostat.


You've got some hot water entering the top, air cools it on the way down,

and by the bottom, it's nice and cool.  Since it's nice and cool, the t- stat

only ingests a bit of it, and recirculates most of it to keep the coolant in the

engine at a toasty 180f or so.  The recirc hose on the t- stat should be too hot to touch, as should

the body of it.


If you heat- soak the engine, it will get hot at the bottom eventually- take off the fan, or block the air from getting into

the radiator and run it

a while.  But it takes a while. 


With the fan, naw, if it's an effective radiator, at idle that motor's not putting out that much heat.


If you want one of the best tools to reassure yourself, go get an infrared thermometer,

and start shooting things.  You'll find that it helps when you see how the fins of the

rad cool as you go down them.



"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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Thanks Carl and thanks Toby for your insights. Carl, it's a new radiator which has been working great, when I blew a hose through it, water came right out, fast and clear. That's what's throwing me - all new parts - should be flowing like a champ.


Toby, I think you hit it spot on - the system is working normally - I'm just not aware (until now) of how a proper cooling system functions (some areas warm, some may stay cool for quite some time) - I think my original diagnosis that higher than normal driving temp and cool lower hose automatically meant a bad thermostat was incorrect.


I think timing was actually the cause of the high temps - I had recently driven the car on a few longer than normal adventures - which threw the timing off a bit (4-speed at 75 mph!) It has been idling funky, and making valve noise ever since. I backed off the distributor a bit, and I think that's helped the temp get back to normal - until I can properly time it and adjust the valves.


I have to agree that I think my cooling system might just super efficient with the new 3-core radiator, new thermostat and new water pump. I can't say enough about having my original radiator recored by Mark at Silicone Garage (BTW, I've seen that he's gone missing - sorry to hear - hope he's okay and that he eventually makes good on anyone he left in the lurch.) Any good radiator shop will be able to recore your original radiator though - made all the difference in my driving temp.


I'm going to drive the car further today - will post again with a follow-up in a few days - thanks again for the great advice!



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Just curious what an average price for a rad garage would be to charge for the 3 core job.

1995 Toyota Landcruiser

1975 2002A

1989 Dodge Raider (sold)

1974 Toyota Landcruiser (very sadly sold)

1994 BMW 530i (sold)

1992 BMW 325i (sold)

1970 2002 auto sunroof (sold)

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Just curious what an average price for a rad garage would be to charge for the 3 core job.


I payed about $450 two years ago - less than a new one - with more cooling capacity than the original - and I liked the idea of having my original radiator rebuilt. They totally rebuild your radiator into a new radiator - so expect that it should cost the price of a new radiator. Any good local radiator shop that recores radiators and cares about their craft should be able to do the job for you.




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 I also have a Silicon Garage 3-row core ...... bought just the core, my local shop did the work.


 Before installing the new 3-row and a new 70-deg thermostat, I had the cooling system flushed twice.  Nowadays, though the engine running temp is always OK, the "system" is still "funny."  When the outside air temp is cold-to-cool, the temp gauge needle hovers at 3 o'clock.  When the outside air temp is over 80 degrees, then the temp needle hovers at 4 o'clock.  In other words, on cold days the engine runs hotter ..... on hot days the engine runs cooler.  Go figure.





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... Before installing the new 3-row and a new 70-deg thermostat, ... In other words, on cold days the engine runs hotter ..... on hot days the engine runs cooler...

With the new rad and a 70deg t-stat you are cooling too much, so the stat is closed more often, giving warmer readings of the recirculated water exiting the block.

On hot days the system is running at proper temps, the stat is open more and less water is recirculated just around the block - giving you normal temp water leaving the block.


Do your car a favor and put a normal stat in and you will get more miles out of it.

JMHO Beaner7102

1971 - 2002 RHD VIN 1653940. Agave (stock with Pertronix & 32/36 Weber) - "Cactus"

1972 - 1602 RHD VIN 1554408. Fjord (with 2L motor, 5spd & LSD - Weber 40/40 to come) - "Bluey"

1984 - E30 318i VIN WBAAK320208722176 - stock daily driver

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