New water pump and overheating problems

R

rov6

New Member
I've replaced the water pump (following joys of snapping 2 bolts, drilling out and cleaning threads and snapping tap off then grinding tap out and helicoiling) and the car now warms up at a normal rate but keeps getting hotter until its just in the red. Then the thermostat opens and it cools to normal. Its then fine if working quite hard (up hill or reasonable speed on the flat) but gets hot again on long, slow down hill runs (its automatic so I think the revs are virtually at idle - series 1 car so no rev counter).

So far I've checked tower waterway is clear (good flow back to radiator). back flushed the system. Taken temperature sender out and put the garden hose on to that waterway for 10 minutes. Cleaned the water system with the 'dishwasher cleaner' method. back flushed it again. Fitted a new thermostat. Following a chat with Pikie at the Bristol classic car show (nice to meet him), I re-filled the cooling system with the front of the car on ramps to ensure all the air came out.

I convinced myself that the bypass pipe must be blocked so removed the pump tonight and its clean and clear.

I've also bought a handheld Infra red temperature reader and the stat is opening at the right temperature and the sender is telling the truth (when its hot on the gauge, that part of the inlet manifold really is hot).

before I changed the pump I've never had overheating problems (owned the car 20 years) and the radiator was new a couple of years ago.

The only thing I can think is that the new pump doesn't pump very well. It looks different inside, the new one having straight impellers and the old curved ones. Does anyone have any advice?

Thanks,
James
 

Attachments

  • DSC_0594.jpg
    DSC_0594.jpg
    44.8 KB · Views: 436
Hi James,

I have used both of those types of water pumps with the impellers shown, and not had any problems from either in terms of increased running temperatures. What I have experienced before is a themostat that does not open until the coolant temp was at or in the red, which you describe.

The thermostats that you have been using, do they have either a jiggle pin or a bleed notch? If they have neither, then that can allow an air pocket to form behind the stat, with the symptoms following that you describe.

Ron.
 
Thank you both for quick responses. It did get hot when left idling for a while but not all the way back into the red. The new thermostat did have the hole in it (I put at the top) and a jiggle pin.
 
Thinking more about your question, Harvey, I've overhauled the carbs and its idling really well now so I've slowed the idle down to about 550 rpm (help the gearbox a bit).
 
First time just put coolant in top of radiator, ran up to temperature at fast idle. Topped up as necessary. Thought I might have air lock so next fill did the same but also took a heater hose off to check. Was coolant there as well. After discussing with Pilkie, put it on ramps for last fill. Same again though. Filled, started and ran at fast idle. Topped up as the air came out.

In between fills and flush, thermostat replacement, I've driven it about 20 miles each time. Not needed any topping up after a drive.
 
You don't need to go to all that trouble to bleed the system of air, and don't run it up to temperature with the cap off. That is the best way to see localised boiling around the exhaust valves.

Fill the radiator, start the engine, bring the level back up the base of the filler tube, put the cap on. Go for a drive, 15 or 20 minutes. Switch the engine off. Next day, take off the radiator cap and start the engine. The level will be down a little as air has now risen to the top of the radiator, top up the coolant to the base of the filler neck, fit the cap and you're done.

On the thermostat front, you don't need to drill a hole in it if it already has a jiggle pin.

There were a lot of dodgy thermostats that came onto the market, and when I had similar problems to what you describe, changing the stat, even 3 or 4 times would eventually cure the running temp problems.

Ron.
 
I suggest you try running it up with the cap off until the stat opens, at which point the level should drop, at that point, with it still running, top it up to just below the neck, then with one hand operate the throttle so it's running at 12-1500rpm, and while it's at that speed, (which should make the level drop again), top up to about 2" below the neck and put then put the cap on. Only then let it come back to idle. You need to get as much coolant in as possible, while still maintaining an air gap.
 
Ok, thanks both for the advice on bleeding the system. Sounds like I should try another thermostat and give it another go.
 
rov6 said:
Ok, thanks both for the advice on bleeding the system. Sounds like I should try another thermostat and give it another go.
Click to expand...


I'd agree it would indicate a faulty thermostat if you had the problem after fitting it, but from how you've written it I take it you had the problem after fitting the pump, and then tried fitting a stat to cure it. That said, there were dodgy stats about, and fitting another one isn't too much trouble.
 
if as you say you are getting a good flow from the carby tower then your water pump is fine, It should be a good strong flow on start up with the water pump dead heading against the thermostat before it opens, then as suggested above try another new thermostat with a reputable brand. test it first in boiling water to see that it fully opens and closes before fitting, and do the same to the old one to see how that has been operating for process of elimination. other than that, you have a good radiator as you mentioned, and I take it you have refitted the cowling around the fan to pull the air through the rad?? then all the best,
Scott
 
westOz74P6B said:
and I take it you have refitted the cowling around the fan to pull the air through the rad?? then all the
Click to expand...

We don't have those in the UK, and I've assumed it's a UK spec car, if not that's a whole different ball game and I'd be checking the viscous coupling as the cowling and the viscous went hand in hand when we did have them here.
 
Thanks for the advice. Yes, it is a uk car. Will get thermostat and put it back together evenings next week.
 
interesting what you mentioned about viscous water pump set up harvey,

the cowling and the viscous went hand in hand when we did have them here.
Click to expand...

So did the UK V8's eventually get the same viscous water pump set up the same as we got here in Australia and NZ from the NZ assembled 3500's, ie the water pumps with the 'long nose' as found on the range rover water pump which had the 'long nose' to suit the viscous hub that was fitted to it?? and can't recall if SD1's had this long nose pump as well but do remember on my '85 that it had a viscous coupling.

If so is there availability of the 'viscous type' water pump in UK as they are becoming (if not already) scarce down under, and would there be a supplier of new pumps rather than exchange??

I had a Gates part number of GWP310 if this is of any help. just wondering, not because I need one, but just if others 'down under' do,
Scott
 
Problem is solved. As a temporary measure I've re-fitted the old pump again and cooling is back to normal again. The symptoms were caused by poor flow. I did discuss the straight impeller pump with 2 mechanical engineers at work who both said it would be much less efficient than the original curved design. I will be avoiding ever fitting a pump the straight type impeller in the future. Thanks everyone for their interest and advice.

James.
 
That is very interesting James. As I mentioned, I have used both types of pump design previously, and never had an obvious problem in terms of cooling. Maybe it was an issue elsewhere that when using the straight bladed impeller pushed your engine into the red. :?

Glad to know that refitting the original pump brought things back to normal.

Ron.
 
I've been thinking about what Ron said about the straight impeller pumps working fine and that there must be something else wrong. Looking carefully at the first picture I can see that the impeller is pushed much farther on to the drive shaft on the new pump. I've taken a second picture to make this clearer. Does anyone have thoughts on the effect this might have? I'm picking your collective brains to see if I should return the newer pump to the supplier.

Thanks.

James
 

Attachments

  • DSC_0609.jpg
    DSC_0609.jpg
    29.1 KB · Views: 150
Hi James,

My understanding is that the smaller the clearance between the impeller and the pump casing, the more efficient the pump will be. There is no fault in the actual casing is there?

I don't disagree that the curved impeller blade is a better design when compared to the straight bladed version, just that when I have used the latter, there was nothing obvious to suggest that something was amiss.

Ron.
 
rov6 said:
Looking carefully at the first picture I can see that the impeller is pushed much farther on to the drive shaft on the new pump. I've taken a second picture to make this clearer. Does anyone have thoughts on the effect this might have? I'm picking your collective brains to see if I should return the newer pump to the supplier.

Thanks.

James
Click to expand...
That could just be that the shaft is a tad longer or has been seated a bit deeper on the bearings and seal and thus is sticking out a bit more. What you need to check is what Ron says, the clearence between the impeller and the casing. I'd suggest a layer of plasticine in the casing and then offering the pump up and then measuring the remaining plasticine in the areas it has been pressed down for clearence.
 
You must log in or register to reply here.
Back
Top