P38A Coolant woes

Howdy friends,

My 01 Rover has been in the wars for a while regarding its cooling system that started with a slow-ish leak a few months ago. I got my local mechanic to have a look while it was in for a service and they said the manifold outlet pipe looked a bit busted and should be replaced. They also mentioned that the top rad hoses were looking a bit fat. So we replaced the manifold and all was good for a few days before it started leaking again.

This one took me a while to figure out, it seemed that coolant was coming out of the overflow hose from the expansion tank, I noticed the coolant expansion tank cap wasn't sitting flush and was a bit warped, so I replaced it, this seemed to do the trick until I took the Rover on a longer journey and found a pool of coolant below the radiator the next morning. I troubleshooted it down to a leaking top rad hose, and seeing as they were a bit fat anyway, I replaced it.

Once again this was all fine on my shorter journey for a few weeks, until I did a longer journey (50 minute drive) and the engine overheated. Interestingly, the Rover was fine the entire drive until I had to stop at traffic lights for a while, when it started again that's when the coolant exploded out of the radiator cap. Coolant was running all over the road. Very good.

Next steps will be to buy a new expansion tank and cap, as the expansion tank thread seems to be munted and is causing the radiator cap to warp. I'm just worried that the system might be over-pressurising, and that's what caused the fat upper rad hoses. I'm fairly confident I did a good job burping the system of air. I'm not sure what else to do :|

Any helpful hints would be greatly appreciated

Check the viscous fan, quite likely it is knackered and not cooling properly, common fault.

Datatek said:

Check the viscous fan, quite likely it is knackered and not cooling properly, common fault.

Click to expand...

Best place to start.
Fan should be stiff to turn first thing in the morning and not spin freely. Start the engine for a couple of minutes then stop again, fan should turn much more easily. Go have a brew and when you're done, fan should be stiff to turn again, though will free up quicker this time around.
If you've got a cheap generic Bluetooth obd reader, you can keep an eye on the engine temp, shouldn't get much above 96 while standing still.
If your top hose goes rock hard, then you have bigger problems

If the fan is working you should hear it roar like a tank when its started then go quiet and roar when it gets hot.

Thanks for the suggestions! I did have a feel of the viscous fan yesterday when the latest episode happened and I thought it felt okay. It was definitely spinning when idling.
I'll try tomorrow when its completely cold!

Is the theory here that if the viscous fan isn't working properly, the coolant will overheat and cause expansion? That would explain the fat pipes and it warping the radiator cap. Driving along the highway should bring enough air in to cool without the fan, right? Then, when I stopped at the set of lights, now the fan is required to bring cold air in. If the fan is faulty, it won't cool correctly then b00m.

If the fan isn't working properly then it will overheat and boil over. You'll also see the temp gauge move to the right.
The fan will always spin, even if the viscous coupling isn't working properly

Try n stop the fan with a rolled up news paper when idling and hot ,if it stops spinning ,its goosed, if you get confetti then bigger problems are afoot,or a dodgy thermostat ,blocked rad ,if its a diesel top baffle might have failed in the radiator O and the water pump could be leaking ,or not pumping ,does the heater go cold in the cab,when on hot ...

I vote rad, probably blocked... try and back flush it.
Some of your symptoms also sound like you may not have fully bled the Air/ left the right gap in the coolant system. But fix the rad first.

My 4 6 did exactly what you described when I got it. A post mortem on the rad revealed the blockages/ rad weld residue.

Alrighty, small update. Investigated the viscous fan and it seemed okay to me, had a good amount of resistance.
Next step is going to be to pull most of the cooling system apart and just replace a bunch of stuff as it all looks very tired after 430,xxx kms and 21 years of use! Definitely need a new expansion tank and cap because its warped.

I don't know who wrote the RAVE manual steps for removing the radiator, but I'll have whatever they were smokin' Looks like I'll need to remove the viscous fan to get the radiator out, as the fan housing is completely blocking the way. Will update once I've investigated!

On the diesel, the rad comes out without the need to remove the viscous fan, once freed off the cowl can be pushed back. I thought on the V8 the cowl was in 2 pieces making it easier.

2 clips on the top of the cowl and drops back.. but the fan removes very easily, worth doing for the few seconds it takes
have you checked coolant flow? take the cap off, start engine and you should see coolant feed back into the tank. it might only be a dribble at idle, but a good steady flow at 1500-2000rpm

2 clips on the top of the cowl and drops back.. but the fan removes very easily, worth doing for the few seconds it takes
have you checked coolant flow? take the cap off, start engine and you should see coolant feed back into the tank. it might only be a dribble at idle, but a good steady flow at 1500-2000rpm

Click to expand...

I removed the cowl, that was fine, but the plastic housing that goes around the rest of the viscous fan was obnoxiously large and in the way.

As for the coolant flow, I have indeed checked it. The method for removing the air was to squeeze the top rad hose, then, while depressed, place finger on the little feedback hole in the expansion tank, then release the top rad hose... rinse and repeat. That had a good flow. And when the car was idle it has a good steady flow.

Quick check of your profile says it's a petrol V8.
Sniff test for exhaust gases in the coolant to try & rule out hg/liner issues as the cause of your overpressurising.

If it's the original radiator then after 21 years & 430,000 km I wouldn't be in the least surprised if it's well bunged up internally.

Check for any odd cold/cool spots & that all the fins are in good condition & that they aren't caked up with mud/debris etc.

Back flushing MIGHT make a difference but IME (1985 3.5 Classic) if it looks dodgy then a replacement or your existing one recored (if possible) would be the better choice. When the original rad on mine finally fell apart the difference in weight between the old & new was considerable!

enjoi said:

I removed the cowl, that was fine, but the plastic housing that goes around the rest of the viscous fan was obnoxiously large and in the way.

As for the coolant flow, I have indeed checked it. The method for removing the air was to squeeze the top rad hose, then, while depressed, place finger on the little feedback hole in the expansion tank, then release the top rad hose... rinse and repeat. That had a good flow. And when the car was idle it has a good steady flow.

Click to expand...

Sounds fine, pls level the coolant cool before replacing the cap. Two spring clips on the cowl top cover, but another two slidy ones to detach the lower cowl, raise it a few cm and then it will cone off its lower lugs and you can hang it over the fan. You will also need to detach the heart to do this, but you have to do that to take the rad out anyway

Ratae said:

If it's the original radiator then after 21 years & 430,000 km I wouldn't be in the least surprised if it's well bunged up internally.

Click to expand...

So here's a fun discovery, I found a receipt for a new radiator 2 years ago as well as a new radiator cap. Surely things wouldn't have gunked up already?

romanrob said:

Sounds fine, pls level the coolant cool before replacing the cap. Two spring clips on the cowl top cover, but another two slidy ones to detach the lower cowl, raise it a few cm and then it will cone off its lower lugs and you can hang it over the fan. You will also need to detach the heart to do this, but you have to do that to take the rad out anyway

Click to expand...

Could you please explain what you mean by "level the coolant" I'm a bit of a noob Thanks for the tips!

Any suggestion that 'stop leak' or 'gasket fix' has been put in the coolant? It will look like glitter in the coolant, maybe dried around the fill area etc.
Nasty stuff that could block the small passageways in a radiator

enjoi said:

So here's a fun discovery, I found a receipt for a new radiator 2 years ago as well as a new radiator cap. Surely things wouldn't have gunked up already?

Click to expand...

Assuming loads of sealants haven't been put in in the intervening period I would hope a 2 year old good quality radiator would still be fine.

kermit_rr said:

Any suggestion that 'stop leak' or 'gasket fix' has been put in the coolant? It will look like glitter in the coolant, maybe dried around the fill area etc.
Nasty stuff that could block the small passageways in a radiator

Click to expand...

Ratae said:

Assuming loads of sealants haven't been put in in the intervening period I would hope a 2 year old good quality radiator would still be fine.

Click to expand...

I did add rear main seal stop-leak fluid to the engine oil a couple of months ago! Nothing in the coolant itself, though.

Problem with all these 'magic fixes' is that whilst they may achieve the desired result they will affect all parts of the relevant system.
The coolant leak stoppers are intended to bung up the leak - but they will also bung up other stuff in the system, esp those with small passages.
The seal leak stoppers generally cause the seal to swell by reacting with the seal material. This may stop the leaky seal, but it will also have the same effect on all the other seals.
Popular with dealers (and private sellers!) to try a cheap fix which they hope will last long enough to sell the car & in the case of the dealer to get past any warranty period.

A sniff test kit for the coolant will rule out the head gaskets.