Radiator blockage?

[db]

Drove to work in the 7 today and noticed the temperature rising (not in my fingers -- just the water).

 

The pipe into the rad were warm and the fan kicked in and was working. The top of the rad was very hot to touch. The pipe out of the bottom of the rad was cold. Coolant levels in the expansion bottle were in range.

 

It sounds like a blockage in the radiator -- is there anything else it could be (there is a bleed nut that I'm scared to touch). Any easy test to do / fix?

 

Current solution will be to run with the heater on full as an alternative cooling circuit (and toast my grateful legs). Any suggestions or views?

[Bob L]

Is your antifreeze mixture up to scratch? You don’t want any frozen bits ☹️

Possible thermostat issue.

Air lock is the most common if recently bled.

 

[db]

Thanks Bob. It's pre-mixed Comma Xtream and the car is garaged so doing think there will have been freezing.

 

I assumed thermostat ok / not an issue as the fan had kicked in and was whirring merrily away.

 

It's a K-series. I have a bleed nut on the radiator and a T in the lower pipe. I think that means it's easy to bleed. A quick search on blatchat doesn't bring up the definite thread on how to bleed it with just a White Suit and an Amex. We can assume low technical knowledge.

[myothercarsa2cv]

Unlikely to be a blockage. And I guess if it was fine before, it's unlikely to be an airlock. My money is on the stat.

 

Quite easy to do, I managed it 😬 You could even go to PRRT to make it easier to swap the stat in the future.

[db]

Hi John - thanks. If the fan is whirring, how does a dud stat affect things? Can it block the flow?

 

I have a pair of ramps I can drive the front wheels up -- do I just run it nice and hot and then open the radiator bleed valve. Should I do this in the burns unit car park?

[Graham King]

db, the stat does block flow but it shouldn't block it as far back as the bottom hose, the stat opens as the water temp on the inlet side of it reaches a specified temperature (82-88 depending on what stat you have fitted). So the bottom hose should get warm even if the stat is jammed. However in this really cold weather I suppose it is possible that the combination of cold air flow and fan running constantly may have allowed the bottom of the rad to cool down significantly.

 

The fan is controlled by the temp switch in the rad so some part of your rad is hot enough to trigger this (approx 96 from memory).

 

What temp did the gauge indicate? did it continue to rise until you switched off or did it stabilise? Did you see what happened if you stayed stationary and ran the engine (i.e. did the bottom hose get warm).

 

Graham.

[db]

Hi Graham -

The top of the radiator was hot hot hot. The crinkly bit and the bottom hose were cold to the touch.

 

Temperature on the gauge was showing 100 (edited from 110) after about 20 mins of commute and when I turned the heater off the temperature gradually rose towards 120 when I shut everything down. My car usually is rock steady on 80 (edited from 100): nothing moves the needle.

 

I ran it again with the covers off to see what happened. Much the same -- temperature started to rise until I got scared and turned it off.

 

 

I'm assuming bleeding is easier than changing the stat? Do I just undo the nut on the rad?

 

 

 

Edited by - db on 21 Nov 2013 23:15:32

[Graham King]

db, 100 sounds really hot for normal running, I suspect the gauge isn't that accurate as at that temp the fan would be on permanently. It should run at (or around) the stat opening temp. I have a K and it runs about 80 (I have an 82 degree stat). The gauge and the fan work off different sensors, the gauge sensor is in the water rail, the fan sensor is in the rad.

 

You're correct it is easier to try to bleed than change the stat (it is very difficult to get at). If it were me I would do the following:

 

1) Let it all cool down and make sure the heater control is open

2) Remove the cap from the expansion tank, remove the screw in the top of the rad, undo the heater hose that connects to the water rail

3) Gently pour some coolant in the hose that you have just undone until water starts to come out of the hole in the top of the rad.

4) Put the rad bleed screw back in and put the hose back on to the heater

5) Grab hold of the bottom hose and manipulate it (a lot)

6) If any air comes out top it back up through the header tank

7) Warm it all up gently feeling all the hoses as they warm, keeping an eye on the temp

 

Graham.

[mav]

Cold outside temps will cause an effct like this. See the late Johnty Lyons posts on this very subject.

 

At Spa earlier in the year, I needed to blank off 2/3's of the rad to get proper running temps and the stat opening as it should. Left to its own devices the bottom hose and hence stat would have remained stone cold whilst top of rad and temp gauge indicated 100+

 

Question, if left idling does the stat open and bottom hose get hot?

[garybee]

Quoting Graham King: 

db, 100 sounds really hot for normal running, I suspect the gauge isn't that accurate as at that temp the fan would be on permanently. It should run at (or around) the stat opening temp. I have a K and it runs about 80 (I have an 82 degree stat). The gauge and the fan work off different sensors, the gauge sensor is in the water rail, the fan sensor is in the rad.

 

The fan won't necessarily run when the engine is at that temp due to the fan sensor being in the position you describe. If coolant isn't circulating through the rad (for whatever reason) the engine will heat up but the fan won't run as the coolant there is still cold.

[db]

I meant 80 not 100. I'm an idiot. Post edited.

 

Drove home this evening -- took 90 mins (with a broken CRB) in slow traffic (better to be the bloke stuck in traffic than the bloke being cut out his vehicle by Trumpton, I reckon).

 

Bloody needle didn't move off 80.

 

This morning was first run for 10 days or so -- perhaps an airlock from...errrr... dunno.

[Graham King]

db, I think what you describe, supports what Mav and I said about cold air flow causing the issue. I would do a stationary warm up over the weekend and check the hoses warm as expected and the temps look fine. If so I would leave it alone and maybe consider blanking off the lower portion of the rad/nose cone to restrict airflow in the colder weather.

 

Graham.

[db]

Thanks Graham -- the CRB has trumped this issue now. I'll* replace thermostat while the engine is out and see what happens, although I'm still guessing a good bleed will do it. I suspect that's a necessary part of putting the engine back in.

[Graham King]

If you are removing the engine anyway then it will be easy to replace the stat, you have 3 options to consider;

 

1) Replace stat as is. If you do this drill a small (3mm) hole in it. It will reduce the need to bleed in the future as it will aloow air locks to bleed past the closed stat.

 

2) Install a PRRT. Rimmer Bros do these. Plenty in archives about installation and benefits.

 

3) Install a PRT. Think Auto do these. Also plenty in archives. I have one of these and used to be a big fan but now not completely convinced if you are driving in cold weather. They're excellent for summer and track days though.

 

2 & 3 are both similar and have the benefit of using a remote stat that is easy to relpace in the future. Whichever one you choose, also consider the temp stat you want to use.

 

Graham.

[db]

Thanks Graham.

[skydragon]

leave it alone and maybe consider blanking off the lower portion of the rad/nose cone to restrict airflow in the colder weather.

*thumbup*

 

If I don't block the bottom half of the rad off in cold weather on my car, I get high temps too. It's counter-intuitive I know but the rad over-cooling part of the cooling circuit can cause the water temps to creep up.