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thejaw77
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61 Posts
Discussion Starter · #1 ·
2001 Discovery 2, 150xxx miles

I have a coolant leak that for the life of me can't seem locate! I have narrowed it down to coolant collecting at the corner bolt where the oil sump connects to the bell-housing just under the starter. It then flows down to the center of the sump/bell-housing dripping onto the crossmember before ending up on the ground. The system holds pressure (tested at 16psi) for about 15 mins before it starts to drop slowly 1 psi every 5-10mins. This issue is causing the coolant to boil after 20 mins of idling the temp gets to 235 before I shut it down. I have the recently replaced the head gaskets and every other gasket this job requires. Right now I have it taken apart to check the valley gasket, head gasket and any other possibilities. As far as I can see it is all dry back there. If anyone has any other ideas I would greatly appreciate some help. Ill try and post some pics when I get the chance.
 

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thejaw77
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61 Posts
Discussion Starter · #3 ·
Thanks for the reply and the suggestion! I should have mentioned that I also just replace the heater core (fun job....not). I have checked the heater core hoses going into the firewall and there isn't any wetness there. Also checked the heater core pipe on other side and still bone dry. I took the starter out to try and get a better look at where the leak might be coming from. Also cleaned the areas around where the coolant is collecting at the mating bolt I mentioned in the original post. Any other suggestions?
 

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'03 Disco SE
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573 Posts
When doing the initial HG job did you get the heads machined? Even if you've never overheated there's a chance of minor warpage which could prevent them from sealing properly.

What about using new head bolts? They're designed to stretch (and act kinda like springs) so if you reused them there's no way you could apply even torque across the block.
 

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thejaw77
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61 Posts
Discussion Starter · #5 ·
Bonsian Discovery - Thanks for the reply! Yes I did get the heads machined and used new bolts when fitting the new head gaskets. On inspecting the heads and valley gasket everything is dry. No coolant in oil or vise versa. I followed the Rave closely and paulp38a.com helped a bunch also. I'm wondering if the front cover gasket (even though I replaced that also) would leak and flow along the top of the oil sump collecting where the sump meets the bell-housing. Anyone seen something like that?
 

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235°F (113°C) is really hot. Aluminium heads generally don't tolerate being overheated once, let alone on a regular basis as you have described.

A coolant leak is one thing but by the sound of things your cooling system is completely ineffective. Does your viscous fan clutch work properly? Is the electric condenser fan operating?

It may not have been the initial cause of the overheating; but I suspect that you now have head gasket trouble. This leads to over pressurization of the cooling system and leaks.

This is just a guess....... do you think the cooling system could be relieving pressure via the expansion tank cap and the overflow tube is spraying coolant around the starting motor?
 

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'03 Disco SE
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573 Posts
235F is pretty damn hot and obviously the engine shouldn't see anywhere near that temp during normal operation, but it's still a bit shy of the "critical" warpage temp of 245F which is often cited for aluminum heads. It *may* have still warped your heads, but if you had them properly decked and torqued it shouldn't be an issue. What device are you using to read temps?

I also don't think the front cover leak is very likely. If it does leak it's usually from the top and is readily visible - I can't imagine that it would migrate all the way back to bellhousing.

I still think it's head gasket related but considering the amount of work you did to the engine there's also an outside chance you installed some component wrong or forgot to tighten something down.

1. Did you get a new reservoir cap? If it's not holding pressure it may be the cause of your boilover.

2. Are you sure you routed the serpentine belt correctly? It will fit "backwards" which would cause your fan to push rather than pull air.

3. Did you get a new thermostat? Are you sure it's installed correctly? If you reversed the installation it could prevent the coolant from reaching the radiator.

4. Is your throttle body heater leaking? Since the leak is at the top of the engine sometimes it finds weird ways around the block and leads you to think it's another symptom.

5. Are you sure all the hoses are routed correctly and the system is bled?

My money is still on the head gasket. The overheating symptoms, the location of the leak, the rapid loss of pressure - it does seem to point to HGs.

I think your next step should be to get a fluorescent dye test kit and a UV light as this will help you nail down the exact location of the leak.
 

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thejaw77
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61 Posts
Discussion Starter · #8 ·
Optimusduff - Thanks for the help! As far as the cooling system I have replaced the viscous fan clutch, radiator, expansion tank cap and heater core. The cooling system takes a good 20-25 mins of idling before temps start to rise. I tested the thermostat in a pot of water to make sure its opening and it does open to what may seem partial. I will replace it with the low temp 180 thermostat along with a new water pump when I put things back together. I have checked the overflow tube to see if coolant sprays but there is nothing while running. Ive only let it get to 235 once. Usually Ill only let it get to 220 during testing before shutdown. The electric condenser fan kicks on at around 210-212 (coolant temp) which I believe is normal. I get plenty of heat in the cabin.
 

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thejaw77
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61 Posts
Discussion Starter · #9 ·
Bosnian Discovery - I agree I think the heads are ok as they were resurfaced and I followed the Rave manual for torque values. Plus I see no leakage or wetness around the heads or valley gasket at the rear of the engine. Also no white smoke from exhaust. Im using a digital scanner to read what the computer is reporting for the coolant temps. I should also mention that I replaced the throttle body heater plate. I also thought maybe I routed the belt incorrectly and went back to check it in a detailed manor and it was installed correctly. During the pressure testing of the cooling system I checked hose routing while making sure coolant was flowing through the hoses (and hoses where warm/hot).
 

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Have you actually taken the Disco for a drive since you did the head gaskets? if not go for a quick run and see if you can "burp" the cooling system. Check your belt routing first as Bosnian Discovery suggests. How are you monitoring your coolant temperature? Scangauge?

I have had trouble getting the air out of my cooling system on several occasions.
 

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thejaw77
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61 Posts
Discussion Starter · #11 ·
Update: I cleaned the back of the engine/bell-housing as best as I could along with the starter area and known coolant leakage flow paths. I am sure now that the coolant is not coming from back of the engine/bell-housing area as it has stayed dry. The coolant continues to collect near the oil sump corner bolt and the area right under the starter on top of oil sump corner. The starter cavity remains dry.
 

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thejaw77
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61 Posts
Discussion Starter · #12 ·
Optimusduff - I did actually take it out for a few test drives around the neighborhood and the engine sounds great with really nice power. No smoke from exhaust. Yes using a scangauge to read the computer temps.
 

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thejaw77
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61 Posts
Discussion Starter · #13 ·
Bosnian Discovery - I think a uv light and dye kit will be a next step when get it back together. I would really like to find this leak though before I put everything back together. Or at least a possibility of where it may be coming from.
 
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