Overheating problem

[Tawny]

The car runs fine if just urban driving, but if I take her out onto national speed limit roads, after a while the fan kicks in and she starts to overheat. If I pull over and stop when she does, I can hear the coolant gurgling from the drivers seat. The only way to keep the temp gauge in the middle is to keep her running below 2500.
I asked a local mechanic I know, but he wasn't sure.
The coolant levels are fine, so it's not that. Any ideas?

 

[mmc757]

Sounds like the pump.
It may be drawing air in through the shaft seal at higher RPM's interfering with coolant flow.

If your heater is also blowing cooler than it should, that would be confirmation of a coolant flow problem.

 

[Tawny]

If your heater is also blowing cooler than it should, that would be confirmation of a coolant flow problem.

Now that you mention it...
Yes, it does seem to suddenly heat up when the gauge hits the red, and things start bubbling. Is that the sort of thing that a dodgy pump would cause?

 

[DOH]

From previously experiencing the same and curing the problem .The following are the things to check:

1) If the Thermostat isn't opening fully, this will cause this issue. So start by purchasing a replacement with seal and change the thermostat for the Eurocarparts Circoli item I have recently posted about.

2) Upon removing the 2 hoses from the thermostat housing , one of them has a restrictor inside the hose .
it is easily identifiable as you will not be able to squash the hose.
On mine I found & there is no mention of this on the forum or elsewhere on the Web that part of the heater matrix core had detached floated along to the restrictor in the pipe and would partially block off the waterflow.
This was incredible hard to find because the hoses are pointing downwards after removal and I had to shine a torch down the hose that revealed what looked like wire brush strands, which I pulled out with long nosed pliers.

So check that carefully as that also causes the problem you have.


3) Flush out in both directions the heater matrix with garden hose , as any debrit or radiator sealand blocks the fine mesh heater matrix.

That can also cause your issue.


4) The water pump can cause the above , but should be showing evidence of red antifreeze loss or a grinding bearing noise if it's on it's way out.

So start with items 1-3 first.

 

[mmc757]

Its the pump.
Doing a coolant flush and fresh thermostat while you have the coolant system open is always a good idea, but I would bet a nice steak dinner that its the pump.

You may not have significant leakage or bearing noise if the mechanical seal is leaking. There should be a little tell-tail weep hole on the pump housing...you may see a snail trail of residue running down from that weep hole, but you might not see actual coolant.