Is my water pump belt slipping?

richardpope50 · Post by **richardpope50** » Sat Sep 07, 2013 6:28 pm

Darkspeed, DaveEFI, Ian …. Thanks ….

Yep, only by-pass is via cabin heater and when that’s off it makes no difference.

Fan is turning correctly and sucking well. At second stage it actually blows into the engine bay cold air so that part of rad is being cooled almost 100% as earlier posts.

I’m really certain the belt is not slipping as there is no sign of it doing so.

If I remove filler plug from rad water comes out, and will also from my new bleed valve if water is warm (expansion pressure). When cold it’s full to brim so no air locks IMHO.

I just can’t believe it’s the pump, somehow.

No other Dax with same radiator as this was designed to maximise cooling(!) as I spent a long time with several rad manufacturers to get it right. Most Dax Rushes use the Dax radiator which is an ali version of a Cortina rad with a pusher fan.

I’m using the MegaSquirt temp sensor that I calibrated - cold, medium and boiling water - and checked with my multi-meter so I know things are accurate here.

It’s Dax Rush (se7en)

Rad height 310mm, width 465mm and core depth 65mm – short, stubby and fat to fit nose cone more or less exactly. Fan is actually 320mm dia and is high capacity at 1,850 CFM so huge capacity.

I have flared side panels so have a very big escape route for hot air.

Now, Ian, your suggestion on making a shroud is exactly what I may try next. However I am unlikely to be able to do it with this high speed fan but should be able to do it with my previous 950 CFM fan as there is no room. Because of how most Dax Rushes are cooled (above) they have fans spanning most of the width so there is very little hot area not at least partially cooled as the fan more or less spans the width of the radiator. In my case 30% is not cooled and I am just wondering is this is the problem.

JSF55 · Post by **JSF55** » Sat Sep 07, 2013 8:06 pm

I'd be sorely tempted to jack the front of the car up and start it from cold, with the pressure cap off to see if it burps into the header tank ?

Ian Anderson · Post by **Ian Anderson** » Sat Sep 07, 2013 9:07 pm

Ok as a comparison my radiator is 300 by 600mm by about 65mm all alloy unit
It lies with the top forward about 100 mm sorobably 60 ish degrees to fit under the low nose
It has two high capacity 12 inch fans on it running at 1580 CFM each
I sat for an hour and a half in a jam in Rouen France 40 degree air temp and fans on manual switch the gauge never moved above low 90. I cooked and the fan V belt struggled with the electric load but the engine never got too hot!

On the GT40 it has nostrils that allow easy exit of the hot air and a mouth about 2/3 area of the rad

So I would think your rad is on the me small size ........ BUT the seven has been done with v8 engines in the past so the size should work

I would suggest checking your temperature readings you may be panicking about nothing

Maplins do a value infra red thermometer for about £25 to help you keep a more accurate check of the inlet and outlet temps

Or if near Heathrow you are welcome to borrow mine

Ian

DEVONMAN · Post by **DEVONMAN** » Sun Sep 08, 2013 8:46 am

Now that you have eliminated the possibility of air locks, here is some further food for thought.

* Did your rad fur up internally slightly when it was off the road dry ?
It really depends on how it was left and how dry it was.

* The main flow through the rad may be down throught the cores directly above the bottom hose. The profile of the top/bottom tanks would normally be shaped/designed to even out flow through the cores.

* Is the thermostat faulty and only just cracking open ?

Just to add,
If the heater circuit is flowing and getting hot then it's unlikely the water pump is not doing it's job, because if it can force coolant through a small bore tube several feet long then it should be able to send coolant through the rad.

You stated earlier that the Air coming from the fan is cool. If it's removing heat from the rad then it should be fairly warm. On my car air coming out of the fan is hot.

richardpope50 · Post by **richardpope50** » Mon Sep 09, 2013 11:24 am

JSF55, Ian and Devonman. Many thanks for all your suggestions and thoughts.

As it is easy to put car on ramps and fire up without pressure cap I’ll try this first.

Temperature Accuracy: No I don’t have an infra-red gun and still really feel the readings are pretty accurate. I’ve calibrated several times using several devices and readings in ambient air, freezer, boiling water and all match across thermometers, ECU’s air temp sender, ECU’s water sender and my multi-meter temperature readings to within a degree or so at least.

Even if the temperature is out, the fan should stabilise the temp and not simply see it keep on increasing.

My point about the fan’s air being cold is that on the low speed the air being sucked through the rad is warm, but on the high speed it is cool. I suggest that this is because there is so much air being sucked through that so much air is passing straight through.

I do think I have pump circulation so agree as above.

My rad design is based on trips to two manufacturers who make bespoke rads. Both ended up with the same design as best for the se7en. The tank is a 40mm high tank top and bottom. Whilst the input is top left and outlet centre bottom, there is an internal pipe to suck from bottom right to maximise the cooling path. I am not sure if there is anything else in the top / bottom tank to shape things.

It fits leaning only a little back from vertical so something like 85 degrees.

My rad is considerably bigger than the standard Dax rad in terms of capacity and some of the Dax rad is below the nose opening and shielded. The Dax rad relies on a big pusher fan.

During the build the rad was left in several stages of water in and water out so I have no idea if it is furred up. Very little rust comes out when draining everything. I may try a rad / engine cleaner, though, just in case.

I agree that the thermostat could be faulty so may change it anyway – worth a try.

Finally, as my fan only covers 70% of the width, that leaves quite a lot of non-cooled rad either side including just above outlet hose so whilst the centre is being cooled right down, when mixed with the really hot water going straight to the outlet, it is not being cooled enough – thus only 15 degree difference.

So my current conclusion is to:
1.) Change stat and flush system with a cleaner.
2.) Devise some fan cowling so at least a full width strip of rad is cooled.

DaveEFI · Post by **DaveEFI** » Mon Sep 09, 2013 3:27 pm

I'd expect the fan and ducting only needed at very slow speeds. Once on the move, airflow through the rad should be more than enough with no fan or ducting.

DEVONMAN · Post by **DEVONMAN** » Mon Sep 09, 2013 4:29 pm

DaveEFI wrote:I'd expect the fan and ducting only needed at very slow speeds. Once on the move, airflow through the rad should be more than enough with no fan or ducting.

Ian Anderson · Post by **Ian Anderson** » Tue Sep 10, 2013 5:50 pm

What are your emissions running at?

Could you be running lean? So much so that it is running real hot?

Sorry just thinking out the box!

Ian

richardpope50 · Post by **richardpope50** » Tue Sep 10, 2013 6:11 pm

DaveEFI wrote:I'd expect the fan and ducting only needed at very slow speeds. Once on the move, airflow through the rad should be more than enough with no fan or ducting.

Yes, but it still needs to be able to idle in traffic and that it cannot do at the moment. Also, at the moment it gets hot when driving just three miles with most of that on country lanes so I'm getting to about 30mph and it needs to cope with that too.

I agree that with a cowl in a rectangle > funnel shape this will significantly reduce the free flow of air at higher speeds and so I guess the fan will be on all / most of the time.

Yes it could be running lean, but could it really be so lean as to be causing such a cooling problem at idle? The map is no doubt out as it is one given to me by the MS supplier as a starter map for my engine.

DaveEFI · Post by **DaveEFI** » Tue Sep 10, 2013 10:36 pm

I'd not expect the fan to be needed at 30 mph. Really just in slow moving traffic.

If the mixture is miles out - or the timing retarded - it will certainly get hotter than it should. Do you have a wideband O2 system fitted?

richardpope50 · Post by **richardpope50** » Wed Sep 11, 2013 9:34 am

Dave,

Yes, I agree.
Yes I agree but what I do not know is by how much hotter (at idle).
Yes - AEM

DaveEFI · Post by **DaveEFI** » Wed Sep 11, 2013 10:30 am

richardpope50 wrote:Dave,

Yes, I agree.
Yes I agree but what I do not know is by how much hotter (at idle).
Yes - AEM

If you have a working wideband O2 sensor, that should rule out a miles too weak AFR. Although I'd be surprised if you got a reliable idle with a too weak mixture. What's the advance at idle?

My SD1 gets at its hottest idling in heavy traffic on a hot day. Goes to 100C.
It has only the temperature controlled viscous coupled mechanical fan - no electric one. On the move it drops back to about 90C.

My idle speed is 600 rpm in drive with an AFR of 13.8:1 according to the O2 sensor (but I'm not sure it is 100% accurate at low revs) and 12 degrees advance. However, mine is a bog standard 3.5 Vitesse EFI. Other versions - especially with a hotter cam - will need different settings.

richardpope50 · Post by **richardpope50** » Wed Sep 11, 2013 4:52 pm

Dave, idle is around 850 / 900. AFR varies around 13 to 15 but normally 14.2 / 14.7. Timing advance is around 15 degrees according to TunerStudio.

Update: I've been able to spend a few hours today on this ..... possible marginal improvement.

First, I totally disconnected my Racelogic unit as whilst it was switched off, it may just interfere especially as it is not set up yet and it's purpose in life is to stop the fuel injectors if it thinks it should. I also note that the ones it does not control, the plugs were more sooty than the others.

Did not change thermostat as it appears to work correctly - opens at about 74. Did not flush rad either as you need to run car for a day or so to clean it with the stuff I have.

Started engine from cold and temp seemed to stabilise at 94. Went for a drive of about three miles at around 40 mph and temp reached 100. Waited for 15 mins to cool down and came home and temp reached 100. Fan on high speed all the time.

Took TunerStudio data logs and also had the VE Live autotune on and updating the changes to the ECU so map has changed a bit.

So some very marginal improvement. I also studied the rad / fan and to be honest there is some 100mm either side of the fan that is not cooled or only very marginally cooled (due to fan being round!).

I think I'll now make up this cowling and see what happens. I can easily back it out.

DaveEFI · Post by **DaveEFI** » Wed Sep 11, 2013 5:50 pm

Something very wrong if a gentle drive through the countryside gets to those sort of temps. Either no airflow through the rad or no water flow.

mgbv8 · Post by **mgbv8** » Wed Sep 11, 2013 6:56 pm

Maybe you could remove the thermostat and do the test run again?