How bad is my radiator

WaltNYC · Jun 29, 2017

My truck builds heat at idle with the A/C on. The temp steadily rises to 210 at which point I lose my nerve and open the windows. Any engine speed above 1200 RPM resolves the situation and temps fall back below 200. Electric condenser fans run normally with A/C on (though frankly I'm not sure how effective they are at the age of 20 years).

I bought myself one of the fancy IR thermometers with the laser sight and last night took some readings of different areas of my radiator. This is what I found....

So, what next? Does this look like a radiator that is clogged or restricted, or a radiator that is doing its job?

Tugela · Jun 29, 2017

How hard does the upper hose get? How much pressure is in the coolant reservoir?

WaltNYC · Jun 29, 2017

upper hose, not firm at all. Res pressure, not much. I replaced the cap on the res last year, but I suspect there may be an issue there.

Tugela · Jun 29, 2017

That's a good sign. It suggests that you have good flow through your cooling system. Neither your radiator nor your heater core sound like they are impeding flow. A little pressure buildup is necessary to circulate, but too much indicates a problem.

WaltNYC · Jun 29, 2017

So where to next? Replace e-fans? or water pump? It is truly puzzling that with the A/C on, at 650-700 RPM my truck is on its way to over-heating, yet at 1500 RPM all is well.

gimebakmybulits · Jun 29, 2017

My 98 would run 212-215 at idle with the A/C on but was fine at speed. Replacing the radiator was my solution, it now runs at 186 (180 tstat) with or without A/C. I did not check temps on the rad like you did though so I can't give you a temp data comparison.

Tugela · Jun 29, 2017

Can you clarify your fan setup? If you are running electric fans (for the radiator, not the AC condenser fans) then that might be a contributing factor. Some folks replace their viscous fan setup with electric units. If you have the viscous fan clutch then you should test that. A viscous fan clutch that is functioning properly will pull a substantial volume of air across the radiator. If your fan clutch isn't engaging at the right point or driving the fan hard enough then this could be a factor in your temps climbing. It's a cheap and quick enough fix (I just did this on my Disco, took ten minutes), although it's worth testing the existing unit first to understand if that's the problem.

Also, is your fan cowl intact and snugly in place? Both the square-ish plastic frame that sits behind the radiator as well as the cap that latches on top? That's an important component in the cooling system as it directs air movement more efficiently.

Even with a new radiator and thermostat my temps fluctuate between idling, driving in heavy traffic, and driving on the freeway. The difference is that the peak is a little lower and the cooling system brings them back down faster.

WaltNYC · Jun 29, 2017

A/C condenser fans and viscous fan clutch are stock. No mods at all. Fan clutch is absolutely engaging (new OEM last summer) as the well known roar of the fan is present and obvious.

Cowl is complete and intact.

The only variable seems to be engine RPM. When in traffic I can put the truck in neutral and use gas pedal to raise RPM to 1200-1500 and temps recede accordingly. Only at idle is it problematic.

Running down the road at any speed above 20 mph with the A/C on my temp settles in around 193-195 even on the hottest days.

At this point I'm trying to decide whether to replace A/C condenser fans, radiator, or water pump first. I'm inclined to start with electric fans because they are easiest to do.

p m · Jun 29, 2017

Walt, FWIW - in all of my trucks, there's approximately 15-degree difference across the top row of the radiator. My guess is the bottom one-third of your radiator is nearly completely clogged up with scale.

Nick - the fact that the top radiator hose is not rock-hard only indicates that there are no exhaust gas leak into the cooling system (no head gasket failure). You can squeeze the hose just fine at coolant temperatures up to 220F.

ptschram · Jun 29, 2017

If it's the stock radiator, replace it!

It's 20 years old!

German Gruner · Jun 29, 2017

Just a couple of little things that help
To unscrew upper radiator frame and wash with hydro washer the straw and insect cumulus between condenser and radiator.
With care you can wash externally radiator panel from rear to front
Part MXC1944 is present? Electric Fans try to force air thru radiator, but if this plate is not present, a lot of flow is lost to the ground.

Regards

Devildog01 · Jun 29, 2017

Instead of wasting money on a infrared heat gun you could just call Erik at Lucky8 and buy a new tstat and radiator. He will also send you pictures of his balls.

JackW · Jun 29, 2017

I've had a lot of experience with clogged radiators in Range Rover classics. They start building up scale in the lower passages due to aluminum from the block transferring scale into the radiator passages. I've found it best to just replace the radiator at around the 120,000 mile mark before the engine overheats and blows a head gasket. At 140K you've definitely gotten the use out of that radiator so replace it now before things get really ugly. And while you're at it if its got those stupid plastic plugs in the radiator replace it with a brass one before it crumbles and causes the engine to overheat.

WaltNYC · Jun 30, 2017

OK, fine. Radiator it is. I'll do the lower hose while I'm at it.

What is the best value in radiators for a very pampered 1997 Discovery these days? I've seen everything from $150 to $500 and beyond. Is a 'three row' really all that important?

No wheeling, just an urban escape vehicle which generally means highway driving and (hopefully) sitting at idle with the A/C on while kids practice various sports so I don't need some super -rugged, over engineered, beast of a unit. That would be a waste of money. Just something that fits properly and cools well under fairly normal conditions.

(yes, I know, I have no business owning this truck given how I use it. But I like it and can maintain it almost entirely myself so I'm gonna hang on until something terminal happens unless someone wants to pay me stupid money for it)

P.S. the fancy infra red thermometer was $12 delivered from Amazon and has already helped me get empirical data from which to form an educated opinion. Far too often I see people just throw parts, time, and effort at these trucks yet end up frustrated. I see no need for a t-stat and certainly am not interested Erik's private parts.

JackW · Jun 30, 2017

I use a local old time radiator shop that has been in business over forty years. If you can find something like that nearby you might be able to get a pretty good price on a replacement without shipping costs. Otherwise shop all of the usual suspect vendors.

p m · Jun 30, 2017

I paid $485 for a complete recore of a D1 radiator here in San Diego. My only regret was that I haven't done it earlier (it happened around 200kmi mark).

gimebakmybulits · Jun 30, 2017

Will Tillery has some D1 takeouts for $150 delivered posted in parts. I bought one of the $250 eBay jobs and it's been just fine.

WaltNYC · Jun 30, 2017

Have always had good experience with Will, and the price is right, but not confident that a used radiator is a good idea.

distrovol · Jun 30, 2017

Had exact same symptoms on my D2 and it was the radiator. Ended up replacing the viscous clutch and t-stat before I got to the actual problem.

Tugela · Jun 30, 2017

WaltNYC said:
Have always had good experience with Will, and the price is right, but not confident that a used radiator is a good idea.

I bought one of Will's used radiators. He said he installed it new in the donor truck and it only had 5,000 miles on it before he pulled it back out. If that's the case, and I have no reason to doubt him, then it should be a sound investment. It's going into my Disco this week, so too soon to tell how the performance is.

Also, on my last Disco, I bought an aluminum aftermarket radiator for about $250. In the two years of ownership after installation it worked great. Then I got rid of the truck so I can't speak to the longevity of the radiator beyond that.

How bad is my radiator

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