Datsun Roadster Forum-311s.org

Hey guys,

What would you think the best course of action would be to cure my cooling problem?

Background,

spl311-09552's r16 will warm up to almost pegged on the temp gauge in about 5 min of driving. I've tried 2 different radiators, one is an original high density 2 row, the other is a re-cored 2-row low density, Density meaning the # of rows per inch and the # of fins per inch. The original has about 2 times the rows per inch compared to the recore. Both radiators are vintage (old). I've tried 160 and 180 thermostats. The system is completely purged. New water pump. I've tried both timing settings for smog and non smog dizzies. I've tried 2 different temp gauges. The only thing i have not swapped is the sending unit, it is frozen in the head to the point the the brass collar to remove the unit snapped off, which means if i re-use this head once i get an h20 block, it will need to be machined out. I'm using the stock metal 4-blade fan with shroud. The expansion tank cap is good and holds pressure. The system does not overheat to the point of puking out water.
I know the head gasket is good. No water in the oil,no bubbles in the system on a leak down test. System does not loose water. If i run cool water on the radiator when it's warm, it will cool down to thermostat setting.

I think the problem is the radiators. They maybe clogged after who knows how many years of neglect.

My question is;
A: Have one of the radiators rodded (cleaned internally) $?
B: Have one of the radiators re-cored with a new high density re-core which runs about $250 here in Las Vegas.
C: Get a new radiator like Steve's or TR's which i think they said runs about $350
D: None of the above because i'm a morron and missed something i should try first.

Any ideas would be appreciated.

Keith

Well, I had a 1600 that was an overheating monster. The first problem was a cooked sending unit. It was no longer accurate. My retaining nut did the same thing yours did. What we did was to drill out the sending unit and then from the thermostat side, punch out the remains of it. The nut was a little more difficult. We used a Dremel tool to grind one side of it through to the threads, then we used a small punch to collapse it into itself. Once we did that, it came out. It took the better part of an afternoon, but it solved the problem. without removing the intake or the head. No machine work either. Once it was out, we just put some teflon tape on the new retaining nut and put the new sender in. It was still an overheater at that point. Apparently, the rear water jackets are marginal. What needed to be done is that the head needed to come off, and then bore brushes of various sizes used to scrub the rear water ports. Remove or open the drain (pre 67.5 had valves on the block while 67.5 and later had a brass plug) and make sure that it flows freely. You would be surprised how many have so much crap in them that the drains no longer work.

Anyway, I would use the above procedure to replace the sender. If that did not solve it, pull the head and commence to scrubbing! Get the radiator checked, and if you need to recore it, get it upgraded to a 3 row.

Thanks Sid,

I was able to remove the sender the way you desribed. I also removed the block drain as it was frozen shut. Once removed, a couple pieces of crap came out the hole but the passage was clear, i could see the cylinder wall and it was surprisingly clean. I connected a high pressure water hose to the inlet in the head above the sender and back-flushed the block for a couple of min while examining the water that came out. Again just a couple of little pieces of crud but that was all. I installed a sender that was in another head that was recently rebuilt. Add coolant/water,purged and ran the engine for 5 min. The temp gauge did not move at all. I grounded out the sending lead and the gauge pegged. so i guess i've got a bad sender now, off to autozone i go for a new sender. The radiator top tank did get warm to hot to the touch in the 5 min it was running. I'm still running the 160* thermostat. I'l try the new sender and fill ya in to what happened.

Keith

If you do the little stuff - thermostat, radiator, etc. - and the car still overheats, it's likely a head gasket leak. I've had this problem. Does the overflow tank get overly pressurized? If you have a leak from exhaust into water, you'll get lots of pressure in the coolant and it'll overheat very quickly.

Of course you need to make sure the temperature is accurate. Use a meat thermometer in the top of the thermostat tower and see if it agrees with your temp. gauge.

part 3

I installed a new wells tu62 sending unit from Autozone for $9.99+ tax. It comes with the collar machined as part of the unit housing. A much higher quality part than stock. Gauge now reads about 195-200 steady as long as i'm moving. It'll rise as soon as i come to an idle, then back down again once i'm moving. This is still with the 160* stat. So i guess it's back to the radiator itself not doing a complete job of cooling. I'm sure in must have a good quantity of clogged rows. I did the meat thermometer in the stat housing and it pegged at 190 (highest reading on the unit). Tomorrow i'll check around and see about just having it rodded.

Keith

Do you still have a fan clutch installed? They are prone to failure. Duct tape or bailing wire (my two favorite things) the fan clutch so that it doesn't slip. See if you still have overheating problems. You should also verify that the water pump is pumping. Pull the upper hose and start it up. See if water comes out. I've bought lots of bad new parts.

I think the best thing going is a Miata radiator swap. Some fab work, but cheap, easy to find, etc.

Next would be a good recore.

Those are probably the best values.

My radiator was embarrasingly expensive, but I didn't want to melt down the drivetrain and turbo's produce a lot of heat.

Congrats on getting that sender out in such short order. I invented a new language consisting entirely of short words in long run on sentances when I removed mine...TR

My 1600 is a 67. It doesn't have a fan clutch. 4 blade metal fan attached directly to the water pump pulley.

TR,
Having all the tools you need to do a job is a big plus. 25+ years of tool hoarding is a good thing. Once i got it in my mind that the job was do-able, i went for it. I used an inpact gun and just burped the gun to remove the 2 water outlets, the one above the sender and the one on the water pump for clearance. Then i pulled the guts out of the sender with some needle nose pliers. I then drilled out the end of the sender and pushed it into the head below the thermostat where i could again grab it with the needle noses. At this point i took the dremel with a 3/8 inch barrel grinder die and slowly removed material on the bottom of the sender and collar until i could just see the threads in the head. I then used a small cold chisel to collapse the sender and collar on itself and used the needle nose to pull out the remnents. All told it was about an hour's worth of carefull (go very slow) work. tools make all the difference.
I was trying to keep spl311-09552 as stock appearing as possible. I already have an sr20-det conversion in progress in the garage so 09552 was to be a stocker if possible. But in the battle of cost vs originality, low cost improvisation is going to win for the time being just to make a runner. I can get an aluminium del sol radiator for about $50. It's a 1" core ( bigger than 2 row, smaller than a 3 row) but cools way better than a 2 row would. I can do the mounting mock-up on the sr20 body than transfer if to 09552. simple right?

Keith

My opinion would be to spend the $250 to have a new 3 core section in the radiator. I just had mine done and my motor stays where it is supposed too. I would have thought initially it would have been the sending unit.

I guess you have been using used radiators in the past??? Just pony up and get a good radiator, its like having insurance down the road. If your car continues to over heat your head may be shaved too much or have a bad head gasket.

Alexi

I didn't think 200 degrees is overheating for a Roadster. Don't these cars run best at 200? My race motors always ran at 200.

If you want to remain stock, a recore is obviously the way to go and will provide plenty of cooling.

For the SR conversion, the $50 aluminum Del Sol unit might work well. You could also test the overheating car on it. Good luck, TR

I had a cooling problem with my 2000. It ran at 195-200 all of the time. I messed around with thermostats but that didn't make any difference. I had the radiator recored and now she runs as cool as a cucumber

Thanks for all of thr replies.

I was pretty sure it was a radiator problem when i started out, but i wanted to be sure i didn't miss an easily overlooked item. Thanks again for all the suggestions.

I'm sure they'll help more people than just myself.

Keith

If it's any help, I have an extra 2000 radiator, tanks are good, core is in rough shape, but if you're going to pay for a recore, might as well upgrade to a 3 row. PM me if interested.

BTW, I took out the freeze plugs and flushed the motor every way I could think of. Probably got about 2 soda cans full of solids, grit, rust flakes and stuff I couldn't even identify. Also, the freeze plugs themselves were about to rust through. Wasn't a fun job, but worth it, would hate to have a freeze plug let go.