Running really hot

satancom · Post by **satancom** » Fri Mar 20, 2009 9:01 am

The new problem in my never ending saga of woe.

My Rover 3.5 V8 is running very hot all of a sudden. A few weeks ago it overheated and spat a load of coolant out. I noticed the temp gauge rising but the engine ran fine. I pulled over and refilled the system after a few mins with 50/50 mix. Maybe 3 litres worth.

The reason it had started to get hot was that the electric fan had failed so even though it was switched on it wasn't doing anything and I was sat in traffic.

So I did a few short journeys in it without a problem, but never really giving it a chance to warm up. I took it for a long drive yesterday evening and it got warm quickly and continued to climb until my oil light flicked on when it was idling in traffic.

I instantly shut it down. Drove it home this morning and it stayed cool but it was early morning so no traffic so I had good airflow.

I have recently fitted new Carbs so maybe mixture related? Maybe the rads full of gunge, although there apeared to be no cool spots on it (it was red hot!

satancom · Post by **satancom** » Fri Mar 20, 2009 9:30 am

Must add that the thermostat is an 82 degree, and a few months old. It apears to be opening fine as the top hose gets warm!

Would a faulty radiator cap give these problems? Just thinking that it opened and dumped my coolant last ime it started to get a touch warm but hasn't done so since!

Ian Anderson · Post by **Ian Anderson** » Fri Mar 20, 2009 10:45 am

Hey Satan
Did you have the internal heater on with hot air coming through?

If so you may have too much flow going through the heater which in turn slows the flow through the radiator. Try closing the heater off and trying again.

It's also worth having a bypass switch on the electric fan so you can turn it on and have it running as you can see the traffic building before the engine get to that temp

Ian

RoverP6B · Post by **RoverP6B** » Fri Mar 20, 2009 10:47 am

The first major overheating when the fan failed could quite possibly have resulted in damage occuring to the thermostat.

As a result, the thermostat now will close during a run without warning, even though everything was fine up until this time.

I have had a number of thermostats over the years doing this very thing.....

Very annoying it is too.

If you change the thermostat, I think you will find the problem solved.

A radiator cap that is not holding pressure can cause coolant to overflow, but only if the temperature is high enough to increase the pressure well beyond the rated 15psi. Once again, the thermostat is the instigator of the problem.

Ron.

satancom · Post by **satancom** » Fri Mar 20, 2009 11:25 am

Well a new thermostat would certainly be a nice easy fix

Lets hope its that. I will pick up a new thermostat this afternoon and replace it. May opt for a cooler one actually.

Out of plain interest I will boil the old one up in a sauce pan to see if it opens!

The heater matrix is permenantly plummed in and has no tap on it. Meaning I only get warm air out of the vents. Would looping it out be a better option? I do not need a cab heater. Its an old land rover with acanvas roof, the manifolds warm the cab up more than the pathetic heater

I could put a manual tap in the hose that feeds the heater matrix and switch it off in the summer if that would help?

satancom · Post by **satancom** » Fri Mar 20, 2009 11:28 am

Also if I can't get a thermostat quickly is it ok to run it with no thermostat? I appriciate an engine runs better warm.. but its a better option than it getting cooked

ChrisJC · Post by **ChrisJC** » Fri Mar 20, 2009 11:41 am

Running with no 'stat is fine - it may well just not warm up properly and drink loads of fuel!

Chris.

ramon alban · Post by **ramon alban** » Fri Mar 20, 2009 11:59 am

Hello Satan,

Personally, from your overall narrative, I fear a new stat may not fix the prob.

# The first or subsequent overheating events may have caused damage - do a compression test on all 8 pots and they should be about 120 to 140 psi, depending upon the state of your engine. Any adjacent pair too low indicates damage to gasket, head or block.

# Is there mayonnaise in the upper parts of the engine - where coolant has gotton into the combustion process, evaporated, steam mixed with oil mist then condenses out on the cooler parts, such as rocker covers, oil filler, breather tubes. etc. leaving an amalgum of water and oil. If so this may confirm overheating damage.

# If the pressure cap is toast - the coolant boils too readily generating steam that will expel coolant, after which the problem worstens. Fix for a few quid.

# Since all this started are you NOW suffering airlocks? - Hard to eliminate on some setups, here is my personal tried and trusted method:

http://www.vintagemodelairplane.com/pag ... ant01.html

satancom · Post by **satancom** » Fri Mar 20, 2009 12:25 pm

Well I managed to find a new stat locally so thats going in later.

I will also flush the radiator out whilst I am at it as the coolant mix is most deffinatly wrong after last night. A compression test is difficult as its a tight old fit in there.. Changing my spark plugs will require some cutting of the foot wells for access (I'll do some holes so they can be bunged).

The engine has about 2000 miles on since new shells/rings/gaskets etc etc! No mayo is present, the exhuast is clear so I am not burning coolant, oil and water is clear. Although I am aware that I could still have a HGF without any signs in the oil.

Again Removing the head sis an engine out job... And I have no garage and a steep driveway

Doing the work is no problem.. Taking the engine in and out of my house is a chore and the misses gets upset!

Darkspeed · Post by **Darkspeed** » Fri Mar 20, 2009 1:40 pm

I would never advise anyone to run without a stat - this can in fact cause overheating.

Without the restriction of the stat the water flow can be too high and pass through the rad without giving up enough heat and return to the engine not cooled.

Race cars running without a stat fit an orifice plate in its place

Andrew

ramon alban · Post by **ramon alban** » Fri Mar 20, 2009 1:41 pm

Oooh Err! You are defo outside my personal comfort zone, and it good to eliminate the possibilities as they are suggested. Keep working your way thro' all of them as best you can, and eventually, as Sherlock says, whatever is left must be the solution.

satancom · Post by **satancom** » Fri Mar 20, 2009 1:47 pm

Hopefully a hose pipe flush of the rad, and a new stat will soft it out.. The block was cleaned out 2000 miles ago so shouldn't have any blockages there. I will check to see its not running lean..

If its anything worse I'll have a little cry !

Ian Anderson · Post by **Ian Anderson** » Fri Mar 20, 2009 1:52 pm

If your heater is in a "full flow" situation all the time this is not too good a thing either as you can get too much fluid using this route and avoiding the rad. This hot water will in turn get back to the engine uncooled and then repeat the process

As a try get some mole grips or clamp and restrict the water flow considerably on the heater route - it then forces the main flow through the rad

IAn

satancom · Post by **satancom** » Fri Mar 20, 2009 2:09 pm

Sounds like a plan.. I'll clanp the pipe and see if it helps, of so I will get some form of valve fitted

Post by **katanaman** » Fri Mar 20, 2009 3:10 pm

On a bad note the rover rarely burns coolant or gets mayo in the oil, usually the compressed gases go into the coolant and over pressure it. A compression test will reveal all or a sniffer test.
On a better note are you sure you don't simply have an airlock? Rover engines are well known for being difficult to purge in some configurations. Filling the system with the front of the engine higher than the back on a jack or up hill can help a fair bit with that.