boreOVERHEATING GRIFF

[FLOODED]

Could someone please help, my Griff 500 still refuses to run at a sensible temp. When i drive down the road the temp does drop straight away, so no engine worries, but it used to happily idle for ages at no more than 95 degrees, but after replacing hoses for silicon, recored rad for alloy radtec rad, standard 82 degree thermostat for large bore 74 degree stat and uprated spool fans, it stays below 90 for about 15mins at idle then creeps upto 100 degrees after around 20mins and blasts coolant past expansion cap (blue cap), no air locks or leaks that i can find. I have no confidence in using it now incase i get stuck in traffic. If i switch off then motor won't restart when too hot.

[spend]

Raise the idle a tad & you may find that makes the water pump circulate enough coolant to solve your worry ~ idling for 15mins is rather extreme?

[RichB]

No ideas, but if it was fine why did you replace all the waterworks fittings?

[Guillotine]

are the fans coming on...and staying on?

should cut in and out around the otter switch value. on 85 off 95.

(does sound like an airlock though)

[Alan Kee]

Try this test:
with the car stationary and the engine running and hot enough for fans to come on, feel the temp of the air coming from the rad .. is the air very hot or cold/cool?

If the system is pumping water at idle then the air will be very hot. If you have a problem with the pump pumping at low revs (a good suggestion and if you have a corroded impeller this would happen) then the water in the rad will be cooled by the fans but not replaced with hot water, so the air drawn through the rad by the fans will be cold, but the water in the engine will get hotter and boil. If you rev the engine in this case does the air from the radiator get hotter? If so replace pump.

If the air through the rad is hot though, that shows your pump is pumping at idle, but the heat from the water isn't being lost quickly enough. When you fitted the new rad did you pay attention to making sure that you blocked any holes off that would allow hot air to recirculate even more easily than normal on a Griff (ie did you fit new foam padding between rad and fibreglass bodywork etc) .. you really need cool air being drawn in the front of the rad, not warm air recirculated from the engine bay.

Also are your fans both sucking through the rad? are they both working?

[heightswitch]

your cap is faulty!

has the cap been replaced?

if you are now boiling up and everything is new / more efficient at dispersing heat then the boiling point has been lowered. Only way of lowering boiling point is to reduce pressure in system, hence cap at fault or cap not sealing effectively against filler neck.

Are you running an expansion bottle?

other possibility is a faulty new stat. Just because it is new doesn;t mean it is any good!!

N

Edited by heightswitch on Tuesday 2nd November 20:13

[rev-erend]

If all this has recently been fitted then it probably just needs bleeding properly.

[nawarne]

[quote=heightswitch]your cap is faulty!

Would not discount this reason!

I had similar problems on my Tuscan in France this summer. The pressure caps were from a company that specialises in German, Swedish & French cars (hint). On two occaisions I had a boil from the cap fitted at the time. Allegedly, both were to OE spec' and manufactured in Germany.

Upshot was that on the Monday after the LeMans Classic I went in to the local VAG dealership purchased a cap with VAG serial number on, and car has been fine ever since (OK, it was Eu 14.7 versus the £3 from the previous supplier).

Good luck with the search for your problem.
Nick

[bigdods]

Alan Kee said:

Also are your fans both sucking through the rad? are they both working?

Check this, make sure your fans are sucking air through the rad and blowing it into the engine bay, not the other way round.

[SUPERCHARGEDEANO]

Thanks for all the advice, have checked everything. Fans run all the time instead of cutting in and out. Have a 74degree large bore thermostat but haven't changed otter switch. Its still got original one fitted.

[bigdods]

SUPERCHARGEDEANO said:

Thanks for all the advice, have checked everything. Fans run all the time instead of cutting in and out. Have a 74degree large bore thermostat but haven't changed otter switch. Its still got original one fitted.

Check the otter by unplugging it. If the fans stop then you know thats the problem. If they keep running then its maybe a faulty relay or wiring.

Doesnt solve overheating though, if the fans are running all the time then it should be runnign cold. Maybe the thermostat is fault and not opening, have you checked you are getting hot water flow to the rad ?

[v8 racing]

Sorry to be the bearer of bad new BUT... if your car is happy to idle a 90 for 15 minutes then start creeping up thats excess pressure getting into the water, i see you have changed quite a bit, with current temperatures and your car idling it should certainly let the fans cut and within a minute they will cut off, Are you certain there are no air locks? when i bleed re fill a system, first thing is to make sure the rad is full, there should be a bleed on the left hand side of the rad, make sure when filling the water system this cap is off, when water is coming out tighten this back of, then find the highest point on the inlet manifold before the stat, on a serp i use the pipe from the inlet manifold to the heater matrix, remove this, put a long funnel in the water tower and fill till the water comes out the pipe, again refit, put the cap back on the water tower, but leave the cap off the expansion tank, run the engine up till the fans cut in fill the expansion tank to 3/4 full, this should be the highest it will come to, IF and i am not saying you have but if it wasnt bled right when you fitted everything there may be a chance of an internal crack, hope not.