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Discussion Starter · #1 ·
Started getting warm couple weeks ago and see bubbles in overflow (like boiling but it's probably air?). Never overheated. If drive around town temp gets 220 then goes down when accelerate (more air to cool). Top hoses are very hot and pressurized. Bottom hose out of the radiator isn't warm at all. Hoses above thermostat are hot. Radiator is about 75 degrees with thermo scanner but shouldn't it be much hotter if coolant is 200+?. I'll test it again. I removed hoses and attached garden hose to top and water comes out of the radiator bottom ok, an coolant came out of the radiator when I took the bottom hose off. 180 degree thermo installed a year ago and new hoses and water pump. Both fans come on ok. I took out the thermostat and dropped in 200 degree water but it didn't open (still in housing since not supposed to remove), but maybe it needed more water? Local mechanic said it failed block test after 10 minutes but didn't try anything else. My thought is that it could be 2 different issues. Any thoughts on the pressure and being hot at the top but cool at the bottom? Could the radiator still be bad and allow water to go through? Anything I can do to check the thermostat to see if it's working properly? Can I bypass the thermostat (how?). Lot's of questions! Thanks for the help.
 

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Discussion Starter · #3 ·
...one more item to add. It is leaking coolant and has been for a while. External head gasket leak but mechanic said it is still external so not getting in oil. But it is leaking more now and have to add 1/2 gallon of coolant every week vs. one gallon every few months before. Hoses seem ok, but can't tell where the leak is from. Could be from the pressure and getting out somewhere?
 

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Cold hose= no stat opening. Use only OEM or MotoRad.

Your radiator could also be plugged. The D2 fan clutch will wear and only partially engage. It's progressive and you don't notice the change in sound.

The truck uses a 18PSI cap. Without cap pressure, you'll reach overheat temp much more quickly. If you keep dicking around and ignoring the HG leak, you're going to find yourself in need of a complete engine.

The discovery never leaks into the crankcase when the head gasket leaks. The passages are too far away. This is a sure fire sign your mechanic doesn't know much about the Rover.
 

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Discussion Starter · #6 ·
Thanks...I'll try a new thermostat first. If this is it then surprised it only lasted a year. Any other way to check to see if the radiator is plugged? The water I put into the top of the radiator came out of the bottom pretty quickly and I didn't have it on very high.
 

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Rule out the coolant tank cap too which means put a new one and tighten it well cos there's no other way, if it fails to seal well can cause the described symptom
 
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It depends on the thermostat you bought. If it was some no-name white box stat from a chain store, I'm surprised it lasted a year. My suggestion would be a MotoRad 439-180.

Keep in mind, there's a trend in the parts industry to put the OEM part number or some other reputable manufacturer's number on off-brand parts. Even though the number matches, it may be a POS.
 

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Discussion Starter · #10 ·
Ok, thanks. Good to know. The newer thermostat has grey housing, not sure what brand. The mechanic put it in. Ordered the MotoRad and a new cap so we'll see what happens. I'll then flush the coolant system while I'm at it. After that I guess my next stop is a radiator but hopefully water coming out of the end pretty quickly when I flushed it is a good sign. But there are 125k miles on it and I've had it since 85k, and don't think it's ever been replaced. Let me know if you have any ideas on something to add when I flush it that may clear any blockages. Thanks again for the help. My mechanic suggested I scrap it since a new engine is $5k+, so trying to do what I can to figure out if it's something else first.
 

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Once you get the thermostat in it, watch the return line at the top of the expansion tank. If you're not getting a good, brisk return flow, you may have a water pump impeller erosion problem. The plastic impellers wear out.

You can't really flush a radiator in a vehicle with a hose. Pull it and take it to a radiator shop. A garden hose amount of flow will be handled by about 10% of your radiator. it can be 90% blocked and still flow coolant. it just won't cool your truck. It won't cool if a 4GPM flow blasts through ten cores. You are better off if half the flow travels slowly through the entire core. What you can do is flush and drive several times to get the old coolant out and replace with the proper spec- like Zerex G-05
 

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No coolant in oil. Since the bottom radiator hose is cold I'm thinking coolant isn't making it out? Is there a bypass or something else I can check? Thanks for the reply.
the HG leak on my truck was at the very back of the passenger side cylinder head. The only way that I could see it was shining a flashlight from the passenger side looking down at the bellhousing where I could then see the telltale sign of a leaky trail that only hit the ground on several occasions throughout course of 1-year. So if it's a slow HG leak at the back you may never see it until it lets go but my guess is that you could get eyes on it if you tried.
 

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You should replace the thermostat/radiator whatever caused the truck to run hot in the first place but the fact remains that you are still losing coolant and HG will have to be replaced sooner than later as it no longer holds water reliably and could cause bigger problems like warpage to the heads as that hot coolant passes more readily, resulting in a loss of pressure and the temp climbs. These engines don't like to be run hot; the coolant temp needs to be 180-190 for reliability sake.
 

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Discussion Starter · #14 ·
I picked up the MotoRad Thermostat today. O'Reilly's had it in stock. Also got a new overflow cap. After installed....max temp idling was 210 then turned the heater back on and it went to 204 and stayed for 20 more minutes. Success!! You all are great. Needless to say I'm going to find another mechanic since this one said for me to scrap my D2. And he only works on Land Rovers so little disappointed but everyone makes mistakes I guess. Thanks again!
 

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Not sure why people are recommending Motorad thermostats?? They have failed many LR owners the last 4-5 years...I had one separate internally myself. The only D2 thermostat anyone should refer people to use is the GENUINE OEM GREY 180*. Available from Lucky8 or AB, basically all LR parts houses carry them now. I wouldn't use the Motorad unless I was in a pinch.
 

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I bought a couple of 180 stats from Brittish parts of Utah
Was sold as o.e.m.
Box was labelled "britpart" as I recall.
No problems
Runs max 189 deg. Usually around 185
 

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Red,
What color is your tstat?
Off-white or gray or?

I would LOVE to run at under 190 (without doing Chubbs' favorite modification).

I am running at about 194 to 199.
In Arizona although how much difference really does the outside temp make at an engine temp of >180?
 

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Temperature is irrelevant as long as your cooling system is capable of keeping the radiator contents under boiling point. Being ten degrees under gets you nothing. Being 20 degrees under gets you the exact same amount of nothing. If you cut your fan belt, your temp is going to climb ten degrees in 20 seconds, so being at 180, 170 or lower gets you zero benefit.

If your cooling system can keep up with the vehicle's and the operating environment's demands, then it's working just fine. If it can't, you either need more air flow or more cooling capacity. The Rover grill sucks for airflow, so modifying it is an option. https://landroverforums.com/forum/discovery-i-39/mesh-grill-write-up-33088/page14/#&gid=1&pid=6 The Rover radiator is not exactly over-sized for the application. Fitting a four-core unit would result in a huge increase in cooling capacity.
 

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Box was labelled "britpart" as I recall.

Runs max 189 deg. Usually around 185
that's cos if they are made by Britpart not just supplied by them probably they are fully opened all the time through the missing bypass flow valve:wink
 

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Temperature is irrelevant as long as your cooling system is capable of keeping the radiator contents under boiling point. Being ten degrees under gets you nothing. Being 20 degrees under gets you the exact same amount of nothing. If you cut your fan belt, your temp is going to climb ten degrees in 20 seconds, so being at 180, 170 or lower gets you zero benefit.

If your cooling system can keep up with the vehicle's and the operating environment's demands, then it's working just fine. If it can't, you either need more air flow or more cooling capacity. The Rover grill sucks for airflow, so modifying it is an option. https://landroverforums.com/forum/discovery-i-39/mesh-grill-write-up-33088/page14/#&gid=1&pid=6 The Rover radiator is not exactly over-sized for the application. Fitting a four-core unit would result in a huge increase in cooling capacity.
I would say your statement "temperature is irrelevant" is a little bit of a stretch on generalization .
You make it sound like a steady 225 would no o.k. Ass long as it doesn't boil which of course isn't true
The reality is things stand up better if you can keep temps under 200. CT..... I'm sure that's why you did your fan mod, others do the thermostat mod, Safari grille mod. Etc. Etc.
 
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