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Cooling System "Refresh"


NAXJA Member
NAXJA Member
I've had a very small leak in my radiator for some time now. It's so slight, there's no coolant on the ground and it takes about 500 miles or so (mostly short distance drives) to require topping off the tank. So it's not been a priority until now. As I prep for my biannual smog test, I decide to finally address it. The radiator was last replaced in 2007 about 35,000 miles ago. If you do the math, that's an average of 2K miles/year. Water pump was changed in 2009. Thermostat and heater valve about 4 years (blew the old heater valve). Fan clutch never (in the 24 years I've owned it). Some of the smaller hoses where changed with the heater valve. The line from the aux cooler to the rad looked a bit sketchy and I was able to find a NOS one. So the time finally came.

I bought a radiator, water pump, fan clutch, fan shroud, thermostat, thermostat housing, radiator fan switch, upper hose, lower hose, hoses from thermostat housing to heater valve, NOS trans cooler line, serpentine belt and some gaskets and antifreeze.

The weekend prior, I ran some radiator flush through the system to clean things out. I pulled off all the hoses and flushed/back flushed the core, the block (as best as I could) and even the leaky radiator. I installed all the new hoses and refilled with fresh coolant. I reflushed the system (no chemicals) when I replaced everything else.

Being in Socal, rust is not really an issue. Except for the water pump bolts, everything came out OK. The water pump bolts did put up a fight despite a generous application of PB Blaster. Turns out the issue was not the bolt threads in the block, but the bolt threads that passed through the water pump were all caked up with corrosion. I did get them all out without breakage. Gave all the hardware a good cleaning, wire wheeling and thread chase.

A few issues. The little rubber isolators that mount in the brackets that hold the condenser to the radiator disintegrated. I manage to jury-rig (or is that jerry-rig) it using some other o-rings, flat washers and some plumbing seals. Seems both solid and allows a bit of flex.

I experience a bit of frustration loosening the belt. I just couldn't reach the bolt just under the PS pump on the backside of the bracket. So I ended up taking the air cleaner box out. Those with a Renix know how perilous this can be with all those small, fragile vacuum lines around it. In the end, it worked out.

On the Renix, the water inlet pipe (line from the heater core) is a straight pipe. I couldn't find one and didn't trust the existing one (on since last water pump change). I bought one for a '91 and later that has the 90 deg bend. This took a bit of trial and error to get the angle correct so I could mount the pump and not have the inlet interfere with other hoses and the ac compressor and bracket.

The aftermarket thermostat housing was a bit taller around the mounting bolts so the bolts I took out didn't have enough thread. I managed to scrounge some hardware form my "old hardware" bin that fit. The lower bolt head is closer to the belt than before but appear to have enough gap. No sign of the belt rubbing.

So I get enough of it back together to fill it, start it up and test for leaks. I don't have the upper radiator support on and have bungee corded the shroud to keep it away from the fan. I pull the fuel pump relay and hit the starter for a few turns. Did this to make sure the belt was seated and aligned. All good. Pop the relay back in and crank 'er up. It lights up and I see a huge spray of transmission fluid! Quickly shut down. Seems I forgot to tighten the upper trans cooler line. OOPS!!! Tighten it down, clean up the mess and try again. Keep checking the coolant level in the tank and top off as needed.

So runs great, kept checking the temp with my IR thermometer and the cluster gauge. At idle didn't go above the 210 line on the gauge. IR showed about 204 at the housing exit to the radiator return. No immediate signs of further leakage (neither green nor red!) Let it idle for 20 minutes at full temp. Shut down, let it cool for about 2 hours. Start it up, get it hot, and let it idle some more. Add coolant to the tank as needed.

Actually did this Sunday and have driven it around including a 30 minute drive. Temps are good, engine tuns good, heater blows out about 130F on full heat.

One thing I did see some trans fluid on the ground Monday morning. I didn't think the trans line leaked and it all looked pretty dry around the fitting. I assumed it was just some residual fluid dripping out from all those little crevices around the structure. So I spent some time with degreaser and brake cleaner making sure I got any old oil and coolant out. Haven't seen any since.

Some pics for you (I know, pics or it didn't happen!)

The parts (I had installed the hoses the week before so they are not showing in this pic).


The old radiator (Note all the green) the other lower corner was just as bad.


My old fan clutch. I suspect this is the original. You can barely see the spring!


The thermostat housing. Note all the pitting where the hose mounts. It's a miracle it didn't leak.


Same with the water pump inlet tube.


The water pump itself still felt good. The bearing was smooth. No sign of coolant in the weep hole. The impeller looks good too.


Sorry for the length of this post. For those that will ask "Why didn't you convert to the open system?" I prefer to keep things as stock as possible. The water valve that blew was also likely the original as I didn't change it prior. I've had only 1 bottle blow up. I have had a ton of cap failures but they went away when I went to the Volvo cap. After that, no further bottle blowups either. So the closed system works just fine for me even in the Socal summer heat.
Sounds like some of the bolts are to long, they are also wet bolts so thread sealant should be used.
So a few more pics for ya.

I cleaned up my old fan clutch a bit to see if there are any markings. These appeared. My guess is this is the original. Completely cold it very hard to spin the "axle". When I shut down (while still cold) the fan would stop turning almost immediately with the old clutch. The new fan clutch will continue spinning for a few seconds. Not bad for 37 years!

old fan clutch.jpg

My old radiator was a CSF 2 row. Not only did it leak but some of the fins corroded away in 2 major spots on the forward side. Still not bad for 17 years! Apparently CSF doesn't make the 2 row anymore and only has the 3 row. This was 2 to 3 times more expensive than the OSC one I bought from RA. Given that I don't tow, don't drive much, and how much I spent on the other parts I'm Ok with it.

old rad 2.jpg

old rad 3.jpg

Old radiator.jpg

Next steps, tune up stuff and smog check.
1988 Laredo - 4L-Auto -2WD - 208K